| Message ID | 20211028093059.32535-3-zajec5@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | [1/3] dt-bindings: watchdog: convert Broadcom's WDT to the json-schema | expand |
On 10/28/21 2:30 AM, Rafał Miłecki wrote: > From: Rafał Miłecki <rafal@milecki.pl> > > Hardware supported by this driver goes back to the old bcm63xx days. It > was then reused in BCM7038 and later also in BCM4908. > > Depending on SoC model registers layout differs a bit. This commit > introduces support for per-chipset registers offsets & adds BCM4908 > layout. > > Later on BCM63xx SoCs support should be added too (probably as platform > devices due to missing DT). Eventually this driver should replace > bcm63xx_wdt.c. > > Signed-off-by: Rafał Miłecki <rafal@milecki.pl> > --- [snip] > + > +static const u16 bcm7038_wdt_regs_bcm4908[] = { > + [BCM63XX_WDT_REG_DEFVAL] = 0x28, > + [BCM63XX_WDT_REG_CTL] = 0x2c, > + [BCM63XX_WDT_REG_SOFTRESET] = 0x34, I don't understand what you are doing here and why you are not offsetting the "reg" property appropriately when you create your bcm4908-wdt Device Tree node such that the base starts at 0, and the existing driver becomes usable as-is. This does not make any sense to me when it is obviously the simplest way to make the driver "accept" the resource being passed. I am going to send my patch series converting the bcm63xx_wdt.c driver over to bcm7038_wdt.c, feel free to use or discard it.
On 10/28/21 9:29 AM, Florian Fainelli wrote: > On 10/28/21 2:30 AM, Rafał Miłecki wrote: >> From: Rafał Miłecki <rafal@milecki.pl> >> >> Hardware supported by this driver goes back to the old bcm63xx days. It >> was then reused in BCM7038 and later also in BCM4908. >> >> Depending on SoC model registers layout differs a bit. This commit >> introduces support for per-chipset registers offsets & adds BCM4908 >> layout. >> >> Later on BCM63xx SoCs support should be added too (probably as platform >> devices due to missing DT). Eventually this driver should replace >> bcm63xx_wdt.c. >> Seems unrelated / irrelevant in this commit log, except maybe after '---'. >> Signed-off-by: Rafał Miłecki <rafal@milecki.pl> >> --- > > [snip] > >> + >> +static const u16 bcm7038_wdt_regs_bcm4908[] = { >> + [BCM63XX_WDT_REG_DEFVAL] = 0x28, REG_DEFVAL is an odd name for this register. I can see that the bcm63xx driver uses it, but in reality it seems to be the timeout value, not some default value, only the bcm63xx driver doesn't seem to use it properly. I think REG_TIMEOUT or similar would be a much better name. >> + [BCM63XX_WDT_REG_CTL] = 0x2c, >> + [BCM63XX_WDT_REG_SOFTRESET] = 0x34, > > I don't understand what you are doing here and why you are not > offsetting the "reg" property appropriately when you create your > bcm4908-wdt Device Tree node such that the base starts at 0, and the > existing driver becomes usable as-is. This does not make any sense to me > when it is obviously the simplest way to make the driver "accept" the > resource being passed. > Agreed. This adds a lot of complexity that could be avoided. > I am going to send my patch series converting the bcm63xx_wdt.c driver > over to bcm7038_wdt.c, feel free to use or discard it. > For my part I am very much looking forward to it. Guenter
[Rob: please kindly comment on this] On 28.10.2021 18:29, Florian Fainelli wrote: > On 10/28/21 2:30 AM, Rafał Miłecki wrote: >> From: Rafał Miłecki <rafal@milecki.pl> >> >> Hardware supported by this driver goes back to the old bcm63xx days. It >> was then reused in BCM7038 and later also in BCM4908. >> >> Depending on SoC model registers layout differs a bit. This commit >> introduces support for per-chipset registers offsets & adds BCM4908 >> layout. >> >> Later on BCM63xx SoCs support should be added too (probably as platform >> devices due to missing DT). Eventually this driver should replace >> bcm63xx_wdt.c. >> >> Signed-off-by: Rafał Miłecki <rafal@milecki.pl> >> --- > > [snip] > >> + >> +static const u16 bcm7038_wdt_regs_bcm4908[] = { >> + [BCM63XX_WDT_REG_DEFVAL] = 0x28, >> + [BCM63XX_WDT_REG_CTL] = 0x2c, >> + [BCM63XX_WDT_REG_SOFTRESET] = 0x34, > > I don't understand what you are doing here and why you are not > offsetting the "reg" property appropriately when you create your > bcm4908-wdt Device Tree node such that the base starts at 0, and the > existing driver becomes usable as-is. This does not make any sense to me > when it is obviously the simplest way to make the driver "accept" the > resource being passed. I believe that DT binding should cover the whole hardware block and describe it (here: use proper compatible to allow recognizing block variant). That's because (as far as I understand) DT should be used to describe hardware as closely as possible. I think it shouldn't be adjusted to make mapping match Linux's driver implementation. So if: 1. Hardware block is mapped at 0xff800400 2. It has interesting registers at 0xff800428 and 0xff80042c I think mapping should use: reg = <0xff800400 0x3c>; even if we don't use the first N registers. That way, at some point, you can extend Linux (or whatever) driver to use extra registers without reworking the whole binding. That's why I think we need to map whole hardware block & handle different registers layouts in a driver. Now, that is something I learnt from various DT discussions but I still may got it wrong. I'd like to ask Rob to comment on this. Let me also paste my summary of BCM4908's block I extracted from Broadcom's header: typedef struct Timer { uint32 TimerCtl0; /* 0x00 */ uint32 TimerCtl1; /* 0x04 */ uint32 TimerCtl2; /* 0x08 */ uint32 TimerCtl3; /* 0x0c */ uint32 TimerCnt0; /* 0x10 */ uint32 TimerCnt1; /* 0x14 */ uint32 TimerCnt2; /* 0x18 */ uint32 TimerCnt3; /* 0x1c */ uint32 TimerMask; /* 0x20 */ uint32 TimerInts; /* 0x24 */ uint32 WatchDogDefCount; /* 0x28 */ uint32 WatchDogCtl; /* 0x2c */ uint32 WDResetCount; /* 0x30 */ uint32 SoftRst; /* 0x34 */ uint32 ResetStatus; /* 0x38 */ uint32 ResetReason; /* 0x3c */ uint32 spare[3]; /* 0x40-0x4b */ };
On 28.10.2021 18:57, Guenter Roeck wrote: > On 10/28/21 9:29 AM, Florian Fainelli wrote: >> On 10/28/21 2:30 AM, Rafał Miłecki wrote: >>> From: Rafał Miłecki <rafal@milecki.pl> >>> >>> Hardware supported by this driver goes back to the old bcm63xx days. It >>> was then reused in BCM7038 and later also in BCM4908. >>> >>> Depending on SoC model registers layout differs a bit. This commit >>> introduces support for per-chipset registers offsets & adds BCM4908 >>> layout. >>> >>> Later on BCM63xx SoCs support should be added too (probably as platform >>> devices due to missing DT). Eventually this driver should replace >>> bcm63xx_wdt.c. >>> > Seems unrelated / irrelevant in this commit log, except maybe after '---'. > >>> Signed-off-by: Rafał Miłecki <rafal@milecki.pl> >>> --- >> >> [snip] >> >>> + >>> +static const u16 bcm7038_wdt_regs_bcm4908[] = { >>> + [BCM63XX_WDT_REG_DEFVAL] = 0x28, > > REG_DEFVAL is an odd name for this register. I can see that the > bcm63xx driver uses it, but in reality it seems to be the timeout > value, not some default value, only the bcm63xx driver doesn't > seem to use it properly. I think REG_TIMEOUT or similar would > be a much better name. I used name used in Broadcom's SDK (and as I guess also in their documentation too). Take a look at this BCM60333 example: typedef struct Timer { uint32 TimerInts; /* 0x00 */ uint32 TimerCtl0; /* 0x04 */ uint32 TimerCtl1; /* 0x08 */ uint32 TimerCtl2; /* 0x0c */ uint32 TimerCnt0; /* 0x10 */ uint32 TimerCnt1; /* 0x14 */ uint32 TimerCnt2; /* 0x18 */ uint32 WatchDogDefCount; /* 0x1c */ uint32 WatchDogCtl; /* 0x20 */ uint32 WDResetCount; /* 0x24 */ } Timer; I got impression that Linux driver registers names usually follow what is used in hardware documentation.
On Fri, Oct 29, 2021 at 01:39:02PM +0200, Rafał Miłecki wrote: > [Rob: please kindly comment on this] > > On 28.10.2021 18:29, Florian Fainelli wrote: > > On 10/28/21 2:30 AM, Rafał Miłecki wrote: > > > From: Rafał Miłecki <rafal@milecki.pl> > > > > > > Hardware supported by this driver goes back to the old bcm63xx days. It > > > was then reused in BCM7038 and later also in BCM4908. > > > > > > Depending on SoC model registers layout differs a bit. This commit > > > introduces support for per-chipset registers offsets & adds BCM4908 > > > layout. > > > > > > Later on BCM63xx SoCs support should be added too (probably as platform > > > devices due to missing DT). Eventually this driver should replace > > > bcm63xx_wdt.c. > > > > > > Signed-off-by: Rafał Miłecki <rafal@milecki.pl> > > > --- > > > > [snip] > > > > > + > > > +static const u16 bcm7038_wdt_regs_bcm4908[] = { > > > + [BCM63XX_WDT_REG_DEFVAL] = 0x28, > > > + [BCM63XX_WDT_REG_CTL] = 0x2c, > > > + [BCM63XX_WDT_REG_SOFTRESET] = 0x34, > > > > I don't understand what you are doing here and why you are not > > offsetting the "reg" property appropriately when you create your > > bcm4908-wdt Device Tree node such that the base starts at 0, and the > > existing driver becomes usable as-is. This does not make any sense to me > > when it is obviously the simplest way to make the driver "accept" the > > resource being passed. > > I believe that DT binding should cover the whole hardware block and > describe it (here: use proper compatible to allow recognizing block > variant). > > That's because (as far as I understand) DT should be used to describe > hardware as closely as possible. I think it shouldn't be adjusted to > make mapping match Linux's driver implementation. > > > So if: > 1. Hardware block is mapped at 0xff800400 > 2. It has interesting registers at 0xff800428 and 0xff80042c > > I think mapping should use: > reg = <0xff800400 0x3c>; > even if we don't use the first N registers. > > That way, at some point, you can extend Linux (or whatever) driver to > use extra registers without reworking the whole binding. That's why I > think we need to map whole hardware block & handle different registers > layouts in a driver. Yes, that's the correct thing to do. The question is whether you'd need sub nodes for the other functions. Folks tend to want to have sub nodes for convenience which isn't really needed and then requires a DT update ('cause they add nodes as adding drivers). Based on the registers, you really don't need sub nodes here. Rob
On 10/29/21 5:15 AM, Rafał Miłecki wrote: > On 28.10.2021 18:57, Guenter Roeck wrote: >> On 10/28/21 9:29 AM, Florian Fainelli wrote: >>> On 10/28/21 2:30 AM, Rafał Miłecki wrote: >>>> From: Rafał Miłecki <rafal@milecki.pl> >>>> >>>> Hardware supported by this driver goes back to the old bcm63xx days. It >>>> was then reused in BCM7038 and later also in BCM4908. >>>> >>>> Depending on SoC model registers layout differs a bit. This commit >>>> introduces support for per-chipset registers offsets & adds BCM4908 >>>> layout. >>>> >>>> Later on BCM63xx SoCs support should be added too (probably as platform >>>> devices due to missing DT). Eventually this driver should replace >>>> bcm63xx_wdt.c. >>>> >> Seems unrelated / irrelevant in this commit log, except maybe after '---'. >> >>>> Signed-off-by: Rafał Miłecki <rafal@milecki.pl> >>>> --- >>> >>> [snip] >>> >>>> + >>>> +static const u16 bcm7038_wdt_regs_bcm4908[] = { >>>> + [BCM63XX_WDT_REG_DEFVAL] = 0x28, >> >> REG_DEFVAL is an odd name for this register. I can see that the >> bcm63xx driver uses it, but in reality it seems to be the timeout >> value, not some default value, only the bcm63xx driver doesn't >> seem to use it properly. I think REG_TIMEOUT or similar would >> be a much better name. > > I used name used in Broadcom's SDK (and as I guess also in their > documentation too). > > Take a look at this BCM60333 example: > > typedef struct Timer { > uint32 TimerInts; /* 0x00 */ > uint32 TimerCtl0; /* 0x04 */ > uint32 TimerCtl1; /* 0x08 */ > uint32 TimerCtl2; /* 0x0c */ > uint32 TimerCnt0; /* 0x10 */ > uint32 TimerCnt1; /* 0x14 */ > uint32 TimerCnt2; /* 0x18 */ > uint32 WatchDogDefCount; /* 0x1c */ > uint32 WatchDogCtl; /* 0x20 */ > uint32 WDResetCount; /* 0x24 */ > } Timer; > > I got impression that Linux driver registers names usually follow what > is used in hardware documentation. Still, the key part of the register name is "Count", not "Def", and there is no "val" in there. Guenter
On 29.10.2021 16:15, Guenter Roeck wrote: > On 10/29/21 5:15 AM, Rafał Miłecki wrote: >> On 28.10.2021 18:57, Guenter Roeck wrote: >>> On 10/28/21 9:29 AM, Florian Fainelli wrote: >>>> On 10/28/21 2:30 AM, Rafał Miłecki wrote: >>>>> From: Rafał Miłecki <rafal@milecki.pl> >>>>> >>>>> Hardware supported by this driver goes back to the old bcm63xx days. It >>>>> was then reused in BCM7038 and later also in BCM4908. >>>>> >>>>> Depending on SoC model registers layout differs a bit. This commit >>>>> introduces support for per-chipset registers offsets & adds BCM4908 >>>>> layout. >>>>> >>>>> Later on BCM63xx SoCs support should be added too (probably as platform >>>>> devices due to missing DT). Eventually this driver should replace >>>>> bcm63xx_wdt.c. >>>>> >>> Seems unrelated / irrelevant in this commit log, except maybe after '---'. >>> >>>>> Signed-off-by: Rafał Miłecki <rafal@milecki.pl> >>>>> --- >>>> >>>> [snip] >>>> >>>>> + >>>>> +static const u16 bcm7038_wdt_regs_bcm4908[] = { >>>>> + [BCM63XX_WDT_REG_DEFVAL] = 0x28, >>> >>> REG_DEFVAL is an odd name for this register. I can see that the >>> bcm63xx driver uses it, but in reality it seems to be the timeout >>> value, not some default value, only the bcm63xx driver doesn't >>> seem to use it properly. I think REG_TIMEOUT or similar would >>> be a much better name. >> >> I used name used in Broadcom's SDK (and as I guess also in their >> documentation too). >> >> Take a look at this BCM60333 example: >> >> typedef struct Timer { >> uint32 TimerInts; /* 0x00 */ >> uint32 TimerCtl0; /* 0x04 */ >> uint32 TimerCtl1; /* 0x08 */ >> uint32 TimerCtl2; /* 0x0c */ >> uint32 TimerCnt0; /* 0x10 */ >> uint32 TimerCnt1; /* 0x14 */ >> uint32 TimerCnt2; /* 0x18 */ >> uint32 WatchDogDefCount; /* 0x1c */ >> uint32 WatchDogCtl; /* 0x20 */ >> uint32 WDResetCount; /* 0x24 */ >> } Timer; >> >> I got impression that Linux driver registers names usually follow what >> is used in hardware documentation. > > Still, the key part of the register name is "Count", not "Def", > and there is no "val" in there. Absolutely right. No idea where did I take it from and how did I miss that.
On 10/29/21 6:03 AM, Rob Herring wrote: > On Fri, Oct 29, 2021 at 01:39:02PM +0200, Rafał Miłecki wrote: >> [Rob: please kindly comment on this] >> >> On 28.10.2021 18:29, Florian Fainelli wrote: >>> On 10/28/21 2:30 AM, Rafał Miłecki wrote: >>>> From: Rafał Miłecki <rafal@milecki.pl> >>>> >>>> Hardware supported by this driver goes back to the old bcm63xx days. It >>>> was then reused in BCM7038 and later also in BCM4908. >>>> >>>> Depending on SoC model registers layout differs a bit. This commit >>>> introduces support for per-chipset registers offsets & adds BCM4908 >>>> layout. >>>> >>>> Later on BCM63xx SoCs support should be added too (probably as platform >>>> devices due to missing DT). Eventually this driver should replace >>>> bcm63xx_wdt.c. >>>> >>>> Signed-off-by: Rafał Miłecki <rafal@milecki.pl> >>>> --- >>> >>> [snip] >>> >>>> + >>>> +static const u16 bcm7038_wdt_regs_bcm4908[] = { >>>> + [BCM63XX_WDT_REG_DEFVAL] = 0x28, >>>> + [BCM63XX_WDT_REG_CTL] = 0x2c, >>>> + [BCM63XX_WDT_REG_SOFTRESET] = 0x34, >>> >>> I don't understand what you are doing here and why you are not >>> offsetting the "reg" property appropriately when you create your >>> bcm4908-wdt Device Tree node such that the base starts at 0, and the >>> existing driver becomes usable as-is. This does not make any sense to me >>> when it is obviously the simplest way to make the driver "accept" the >>> resource being passed. >> >> I believe that DT binding should cover the whole hardware block and >> describe it (here: use proper compatible to allow recognizing block >> variant). >> >> That's because (as far as I understand) DT should be used to describe >> hardware as closely as possible. I think it shouldn't be adjusted to >> make mapping match Linux's driver implementation. >> >> >> So if: >> 1. Hardware block is mapped at 0xff800400 >> 2. It has interesting registers at 0xff800428 and 0xff80042c >> >> I think mapping should use: >> reg = <0xff800400 0x3c>; >> even if we don't use the first N registers. >> >> That way, at some point, you can extend Linux (or whatever) driver to >> use extra registers without reworking the whole binding. That's why I >> think we need to map whole hardware block & handle different registers >> layouts in a driver. > > Yes, that's the correct thing to do. So in the future if we happen to want to manage the hardware timers in that block, they would be part of the watchdog driver? I am fairly sure they won't be, so you will be creating a composite driver/MFD to separate out the functions, more likely. So you might as well create sub-nodes. > > The question is whether you'd need sub nodes for the other functions. > Folks tend to want to have sub nodes for convenience which isn't really > needed and then requires a DT update ('cause they add nodes as adding > drivers). Sorry but not, this is getting completely ridiculous, the > > Based on the registers, you really don't need sub nodes here. I sort of disagree here, the watchdog is a part of a sundry timer block here, but it is logically broken up into different parts and if if I were to imagine how this would map into different drivers, I can easily see that we would have: - a driver to manage the timer interrupt controller - a driver to manage each of the 3 hardware timers, be they clockevent or else - a driver to manage the watchdog The simplest way to get there, and also because these same timer blocks are actually spread in other parts of STB chips just like the watchdog is, but in a different layout where they stand on their own was the main drive for defining the bcm7038_wdt binding the way it was. Rafal, I appreciate that you are trying to leverage the bcm7038_wdt driver and this is better than the previous patch set, but I really do not see why having the watchdog driver not manage the *exact* subset of the register space needed (starting at 0x28) is not being done. -- Florian
On 29.10.2021 18:45, Florian Fainelli wrote: > On 10/29/21 6:03 AM, Rob Herring wrote: >> On Fri, Oct 29, 2021 at 01:39:02PM +0200, Rafał Miłecki wrote: >>> [Rob: please kindly comment on this] >>> >>> On 28.10.2021 18:29, Florian Fainelli wrote: >>>> On 10/28/21 2:30 AM, Rafał Miłecki wrote: >>>>> From: Rafał Miłecki <rafal@milecki.pl> >>>>> >>>>> Hardware supported by this driver goes back to the old bcm63xx days. It >>>>> was then reused in BCM7038 and later also in BCM4908. >>>>> >>>>> Depending on SoC model registers layout differs a bit. This commit >>>>> introduces support for per-chipset registers offsets & adds BCM4908 >>>>> layout. >>>>> >>>>> Later on BCM63xx SoCs support should be added too (probably as platform >>>>> devices due to missing DT). Eventually this driver should replace >>>>> bcm63xx_wdt.c. >>>>> >>>>> Signed-off-by: Rafał Miłecki <rafal@milecki.pl> >>>>> --- >>>> >>>> [snip] >>>> >>>>> + >>>>> +static const u16 bcm7038_wdt_regs_bcm4908[] = { >>>>> + [BCM63XX_WDT_REG_DEFVAL] = 0x28, >>>>> + [BCM63XX_WDT_REG_CTL] = 0x2c, >>>>> + [BCM63XX_WDT_REG_SOFTRESET] = 0x34, >>>> >>>> I don't understand what you are doing here and why you are not >>>> offsetting the "reg" property appropriately when you create your >>>> bcm4908-wdt Device Tree node such that the base starts at 0, and the >>>> existing driver becomes usable as-is. This does not make any sense to me >>>> when it is obviously the simplest way to make the driver "accept" the >>>> resource being passed. >>> >>> I believe that DT binding should cover the whole hardware block and >>> describe it (here: use proper compatible to allow recognizing block >>> variant). >>> >>> That's because (as far as I understand) DT should be used to describe >>> hardware as closely as possible. I think it shouldn't be adjusted to >>> make mapping match Linux's driver implementation. >>> >>> >>> So if: >>> 1. Hardware block is mapped at 0xff800400 >>> 2. It has interesting registers at 0xff800428 and 0xff80042c >>> >>> I think mapping should use: >>> reg = <0xff800400 0x3c>; >>> even if we don't use the first N registers. >>> >>> That way, at some point, you can extend Linux (or whatever) driver to >>> use extra registers without reworking the whole binding. That's why I >>> think we need to map whole hardware block & handle different registers >>> layouts in a driver. >> >> Yes, that's the correct thing to do. > > So in the future if we happen to want to manage the hardware timers in > that block, they would be part of the watchdog driver? I am fairly sure > they won't be, so you will be creating a composite driver/MFD to > separate out the functions, more likely. So you might as well create > sub-nodes. > >> >> The question is whether you'd need sub nodes for the other functions. >> Folks tend to want to have sub nodes for convenience which isn't really >> needed and then requires a DT update ('cause they add nodes as adding >> drivers). > > Sorry but not, this is getting completely ridiculous, the > >> >> Based on the registers, you really don't need sub nodes here. > > I sort of disagree here, the watchdog is a part of a sundry timer block > here, but it is logically broken up into different parts and if if I > were to imagine how this would map into different drivers, I can easily > see that we would have: > > - a driver to manage the timer interrupt controller > - a driver to manage each of the 3 hardware timers, be they clockevent > or else > - a driver to manage the watchdog > > The simplest way to get there, and also because these same timer blocks > are actually spread in other parts of STB chips just like the watchdog > is, but in a different layout where they stand on their own was the main > drive for defining the bcm7038_wdt binding the way it was. > > Rafal, I appreciate that you are trying to leverage the bcm7038_wdt > driver and this is better than the previous patch set, but I really do > not see why having the watchdog driver not manage the *exact* subset of > the register space needed (starting at 0x28) is not being done. Sure, let's get this discussed before pushing my patches. I'm happy to have you and Rob involved here. Once we get into agreement we can decide how to proceed.
On 10/29/21 9:45 AM, Florian Fainelli wrote: > On 10/29/21 6:03 AM, Rob Herring wrote: >> On Fri, Oct 29, 2021 at 01:39:02PM +0200, Rafał Miłecki wrote: >>> [Rob: please kindly comment on this] >>> >>> On 28.10.2021 18:29, Florian Fainelli wrote: >>>> On 10/28/21 2:30 AM, Rafał Miłecki wrote: >>>>> From: Rafał Miłecki <rafal@milecki.pl> >>>>> >>>>> Hardware supported by this driver goes back to the old bcm63xx days. It >>>>> was then reused in BCM7038 and later also in BCM4908. >>>>> >>>>> Depending on SoC model registers layout differs a bit. This commit >>>>> introduces support for per-chipset registers offsets & adds BCM4908 >>>>> layout. >>>>> >>>>> Later on BCM63xx SoCs support should be added too (probably as platform >>>>> devices due to missing DT). Eventually this driver should replace >>>>> bcm63xx_wdt.c. >>>>> >>>>> Signed-off-by: Rafał Miłecki <rafal@milecki.pl> >>>>> --- >>>> >>>> [snip] >>>> >>>>> + >>>>> +static const u16 bcm7038_wdt_regs_bcm4908[] = { >>>>> + [BCM63XX_WDT_REG_DEFVAL] = 0x28, >>>>> + [BCM63XX_WDT_REG_CTL] = 0x2c, >>>>> + [BCM63XX_WDT_REG_SOFTRESET] = 0x34, >>>> >>>> I don't understand what you are doing here and why you are not >>>> offsetting the "reg" property appropriately when you create your >>>> bcm4908-wdt Device Tree node such that the base starts at 0, and the >>>> existing driver becomes usable as-is. This does not make any sense to me >>>> when it is obviously the simplest way to make the driver "accept" the >>>> resource being passed. >>> >>> I believe that DT binding should cover the whole hardware block and >>> describe it (here: use proper compatible to allow recognizing block >>> variant). >>> >>> That's because (as far as I understand) DT should be used to describe >>> hardware as closely as possible. I think it shouldn't be adjusted to >>> make mapping match Linux's driver implementation. >>> >>> >>> So if: >>> 1. Hardware block is mapped at 0xff800400 >>> 2. It has interesting registers at 0xff800428 and 0xff80042c >>> >>> I think mapping should use: >>> reg = <0xff800400 0x3c>; >>> even if we don't use the first N registers. >>> >>> That way, at some point, you can extend Linux (or whatever) driver to >>> use extra registers without reworking the whole binding. That's why I >>> think we need to map whole hardware block & handle different registers >>> layouts in a driver. >> >> Yes, that's the correct thing to do. > > So in the future if we happen to want to manage the hardware timers in > that block, they would be part of the watchdog driver? I am fairly sure > they won't be, so you will be creating a composite driver/MFD to > separate out the functions, more likely. So you might as well create > sub-nodes. > >> >> The question is whether you'd need sub nodes for the other functions. >> Folks tend to want to have sub nodes for convenience which isn't really >> needed and then requires a DT update ('cause they add nodes as adding >> drivers). > > Sorry but not, this is getting completely ridiculous, the > >> >> Based on the registers, you really don't need sub nodes here. > > I sort of disagree here, the watchdog is a part of a sundry timer block > here, but it is logically broken up into different parts and if if I > were to imagine how this would map into different drivers, I can easily > see that we would have: > > - a driver to manage the timer interrupt controller > - a driver to manage each of the 3 hardware timers, be they clockevent > or else > - a driver to manage the watchdog > > The simplest way to get there, and also because these same timer blocks > are actually spread in other parts of STB chips just like the watchdog > is, but in a different layout where they stand on their own was the main > drive for defining the bcm7038_wdt binding the way it was. > > Rafal, I appreciate that you are trying to leverage the bcm7038_wdt > driver and this is better than the previous patch set, but I really do > not see why having the watchdog driver not manage the *exact* subset of > the register space needed (starting at 0x28) is not being done. Agreed, especially since other sub-devices of bcm4908 are alredy modeled this way. See arch/arm64/boot/dts/broadcom/bcm4908/bcm4908.dtsi. At this point, before accepting anything, I'll want to have an explanation how and why the watchdog interface is handled differently than, say, its reset controller. Also, I'd like to understand the memory region assigned to bcm7038, which happens to be something like: compatible = "brcm,bcm7038-wdt"; reg = <0xf040a7e8 0x16>; because it seems unlikely that this is a chip subsystem that just happens to start at such an odd boundary. More specifically, I see in actual .dtsi files data such as: watchdog: watchdog@4066a8 { clocks = <&upg_clk>; compatible = "brcm,bcm7038-wdt"; reg = <0x4066a8 0x14>; status = "disabled"; }; ... timers: timer@406680 { compatible = "brcm,brcmstb-timers"; reg = <0x406680 0x40>; }; So there happen to be timers in the same region, and the offset between timer and watchdog registers is 0x28. Coincidentally, that just happens to be the extra offset defined in this patch for the bcm4908 watchdog. Really ? Sorry, this sounds very inconsistent and arbitrary to me. Overall, I suspect I'll have to see datasheets if we really end up having different offsets for each chip, because I'll want to confirm that the watchdog subsystem isn't treated differently than other subsystems, and that the offset calculations are appropriate and consistent across the different chips. Guenter
On 10/29/21 10:43 AM, Guenter Roeck wrote: > On 10/29/21 9:45 AM, Florian Fainelli wrote: >> On 10/29/21 6:03 AM, Rob Herring wrote: >>> On Fri, Oct 29, 2021 at 01:39:02PM +0200, Rafał Miłecki wrote: >>>> [Rob: please kindly comment on this] >>>> >>>> On 28.10.2021 18:29, Florian Fainelli wrote: >>>>> On 10/28/21 2:30 AM, Rafał Miłecki wrote: >>>>>> From: Rafał Miłecki <rafal@milecki.pl> >>>>>> >>>>>> Hardware supported by this driver goes back to the old bcm63xx >>>>>> days. It >>>>>> was then reused in BCM7038 and later also in BCM4908. >>>>>> >>>>>> Depending on SoC model registers layout differs a bit. This commit >>>>>> introduces support for per-chipset registers offsets & adds BCM4908 >>>>>> layout. >>>>>> >>>>>> Later on BCM63xx SoCs support should be added too (probably as >>>>>> platform >>>>>> devices due to missing DT). Eventually this driver should replace >>>>>> bcm63xx_wdt.c. >>>>>> >>>>>> Signed-off-by: Rafał Miłecki <rafal@milecki.pl> >>>>>> --- >>>>> >>>>> [snip] >>>>> >>>>>> + >>>>>> +static const u16 bcm7038_wdt_regs_bcm4908[] = { >>>>>> + [BCM63XX_WDT_REG_DEFVAL] = 0x28, >>>>>> + [BCM63XX_WDT_REG_CTL] = 0x2c, >>>>>> + [BCM63XX_WDT_REG_SOFTRESET] = 0x34, >>>>> >>>>> I don't understand what you are doing here and why you are not >>>>> offsetting the "reg" property appropriately when you create your >>>>> bcm4908-wdt Device Tree node such that the base starts at 0, and the >>>>> existing driver becomes usable as-is. This does not make any sense >>>>> to me >>>>> when it is obviously the simplest way to make the driver "accept" the >>>>> resource being passed. >>>> >>>> I believe that DT binding should cover the whole hardware block and >>>> describe it (here: use proper compatible to allow recognizing block >>>> variant). >>>> >>>> That's because (as far as I understand) DT should be used to describe >>>> hardware as closely as possible. I think it shouldn't be adjusted to >>>> make mapping match Linux's driver implementation. >>>> >>>> >>>> So if: >>>> 1. Hardware block is mapped at 0xff800400 >>>> 2. It has interesting registers at 0xff800428 and 0xff80042c >>>> >>>> I think mapping should use: >>>> reg = <0xff800400 0x3c>; >>>> even if we don't use the first N registers. >>>> >>>> That way, at some point, you can extend Linux (or whatever) driver to >>>> use extra registers without reworking the whole binding. That's why I >>>> think we need to map whole hardware block & handle different registers >>>> layouts in a driver. >>> >>> Yes, that's the correct thing to do. >> >> So in the future if we happen to want to manage the hardware timers in >> that block, they would be part of the watchdog driver? I am fairly sure >> they won't be, so you will be creating a composite driver/MFD to >> separate out the functions, more likely. So you might as well create >> sub-nodes. >> >>> >>> The question is whether you'd need sub nodes for the other functions. >>> Folks tend to want to have sub nodes for convenience which isn't really >>> needed and then requires a DT update ('cause they add nodes as adding >>> drivers). >> >> Sorry but not, this is getting completely ridiculous, the >> >>> >>> Based on the registers, you really don't need sub nodes here. >> >> I sort of disagree here, the watchdog is a part of a sundry timer block >> here, but it is logically broken up into different parts and if if I >> were to imagine how this would map into different drivers, I can easily >> see that we would have: >> >> - a driver to manage the timer interrupt controller >> - a driver to manage each of the 3 hardware timers, be they clockevent >> or else >> - a driver to manage the watchdog >> >> The simplest way to get there, and also because these same timer blocks >> are actually spread in other parts of STB chips just like the watchdog >> is, but in a different layout where they stand on their own was the main >> drive for defining the bcm7038_wdt binding the way it was. >> >> Rafal, I appreciate that you are trying to leverage the bcm7038_wdt >> driver and this is better than the previous patch set, but I really do >> not see why having the watchdog driver not manage the *exact* subset of >> the register space needed (starting at 0x28) is not being done. > > Agreed, especially since other sub-devices of bcm4908 are alredy modeled > this way. See arch/arm64/boot/dts/broadcom/bcm4908/bcm4908.dtsi. > At this point, before accepting anything, I'll want to have an explanation > how and why the watchdog interface is handled differently than, say, > its reset controller. Also, I'd like to understand the memory region > assigned to bcm7038, which happens to be something like: > > compatible = "brcm,bcm7038-wdt"; > reg = <0xf040a7e8 0x16>; > > because it seems unlikely that this is a chip subsystem that just happens > to start at such an odd boundary. More specifically, I see in actual > .dtsi files data such as: > > watchdog: watchdog@4066a8 { > clocks = <&upg_clk>; > compatible = "brcm,bcm7038-wdt"; > reg = <0x4066a8 0x14>; > status = "disabled"; > }; > ... > timers: timer@406680 { > compatible = "brcm,brcmstb-timers"; > reg = <0x406680 0x40>; > }; > > So there happen to be timers in the same region, and the offset > between timer and watchdog registers is 0x28. Coincidentally, that > just happens to be the extra offset defined in this patch for the > bcm4908 watchdog. Really ? Sorry, this sounds very inconsistent > and arbitrary to me. To Rafal's defense, we could have defined the bcm7038-wdt binding such that the watchdog would have been at 0x28 from the beginning of the timer block, but as I wrote earlier, that same watchdog which is really just 8 bytes worth of register is sometimes instantiated on its own without the rest of the timer block. This is not visible in a DTS that is upstream but it does happen in some of the Cable Modem chips. That was the main motivation for defining the binding the way it was, such that we could just map those 8 bytes wherever they are. > > Overall, I suspect I'll have to see datasheets if we really end up > having different offsets for each chip, because I'll want to confirm > that the watchdog subsystem isn't treated differently than other > subsystems, and that the offset calculations are appropriate and > consistent across the different chips. Datasheets are not public however sharing the structures documenting the register layout is something that is possible. For consistency, if we do let 4908 define the watchdog to include that 0x28 offset, then we are not mapping just the watchdog, but the entire timer block, which then raises the question of what happens to the timer interrupt enable/status and timer registers, how do we end-up sub-dividing that register space in a logical manner.
On 10/29/21 10:53 AM, Florian Fainelli wrote: > On 10/29/21 10:43 AM, Guenter Roeck wrote: >> On 10/29/21 9:45 AM, Florian Fainelli wrote: >>> On 10/29/21 6:03 AM, Rob Herring wrote: >>>> On Fri, Oct 29, 2021 at 01:39:02PM +0200, Rafał Miłecki wrote: >>>>> [Rob: please kindly comment on this] >>>>> >>>>> On 28.10.2021 18:29, Florian Fainelli wrote: >>>>>> On 10/28/21 2:30 AM, Rafał Miłecki wrote: >>>>>>> From: Rafał Miłecki <rafal@milecki.pl> >>>>>>> >>>>>>> Hardware supported by this driver goes back to the old bcm63xx >>>>>>> days. It >>>>>>> was then reused in BCM7038 and later also in BCM4908. >>>>>>> >>>>>>> Depending on SoC model registers layout differs a bit. This commit >>>>>>> introduces support for per-chipset registers offsets & adds BCM4908 >>>>>>> layout. >>>>>>> >>>>>>> Later on BCM63xx SoCs support should be added too (probably as >>>>>>> platform >>>>>>> devices due to missing DT). Eventually this driver should replace >>>>>>> bcm63xx_wdt.c. >>>>>>> >>>>>>> Signed-off-by: Rafał Miłecki <rafal@milecki.pl> >>>>>>> --- >>>>>> >>>>>> [snip] >>>>>> >>>>>>> + >>>>>>> +static const u16 bcm7038_wdt_regs_bcm4908[] = { >>>>>>> + [BCM63XX_WDT_REG_DEFVAL] = 0x28, >>>>>>> + [BCM63XX_WDT_REG_CTL] = 0x2c, >>>>>>> + [BCM63XX_WDT_REG_SOFTRESET] = 0x34, >>>>>> >>>>>> I don't understand what you are doing here and why you are not >>>>>> offsetting the "reg" property appropriately when you create your >>>>>> bcm4908-wdt Device Tree node such that the base starts at 0, and the >>>>>> existing driver becomes usable as-is. This does not make any sense >>>>>> to me >>>>>> when it is obviously the simplest way to make the driver "accept" the >>>>>> resource being passed. >>>>> >>>>> I believe that DT binding should cover the whole hardware block and >>>>> describe it (here: use proper compatible to allow recognizing block >>>>> variant). >>>>> >>>>> That's because (as far as I understand) DT should be used to describe >>>>> hardware as closely as possible. I think it shouldn't be adjusted to >>>>> make mapping match Linux's driver implementation. >>>>> >>>>> >>>>> So if: >>>>> 1. Hardware block is mapped at 0xff800400 >>>>> 2. It has interesting registers at 0xff800428 and 0xff80042c >>>>> >>>>> I think mapping should use: >>>>> reg = <0xff800400 0x3c>; >>>>> even if we don't use the first N registers. >>>>> >>>>> That way, at some point, you can extend Linux (or whatever) driver to >>>>> use extra registers without reworking the whole binding. That's why I >>>>> think we need to map whole hardware block & handle different registers >>>>> layouts in a driver. >>>> >>>> Yes, that's the correct thing to do. >>> >>> So in the future if we happen to want to manage the hardware timers in >>> that block, they would be part of the watchdog driver? I am fairly sure >>> they won't be, so you will be creating a composite driver/MFD to >>> separate out the functions, more likely. So you might as well create >>> sub-nodes. >>> >>>> >>>> The question is whether you'd need sub nodes for the other functions. >>>> Folks tend to want to have sub nodes for convenience which isn't really >>>> needed and then requires a DT update ('cause they add nodes as adding >>>> drivers). >>> >>> Sorry but not, this is getting completely ridiculous, the >>> >>>> >>>> Based on the registers, you really don't need sub nodes here. >>> >>> I sort of disagree here, the watchdog is a part of a sundry timer block >>> here, but it is logically broken up into different parts and if if I >>> were to imagine how this would map into different drivers, I can easily >>> see that we would have: >>> >>> - a driver to manage the timer interrupt controller >>> - a driver to manage each of the 3 hardware timers, be they clockevent >>> or else >>> - a driver to manage the watchdog >>> >>> The simplest way to get there, and also because these same timer blocks >>> are actually spread in other parts of STB chips just like the watchdog >>> is, but in a different layout where they stand on their own was the main >>> drive for defining the bcm7038_wdt binding the way it was. >>> >>> Rafal, I appreciate that you are trying to leverage the bcm7038_wdt >>> driver and this is better than the previous patch set, but I really do >>> not see why having the watchdog driver not manage the *exact* subset of >>> the register space needed (starting at 0x28) is not being done. >> >> Agreed, especially since other sub-devices of bcm4908 are alredy modeled >> this way. See arch/arm64/boot/dts/broadcom/bcm4908/bcm4908.dtsi. >> At this point, before accepting anything, I'll want to have an explanation >> how and why the watchdog interface is handled differently than, say, >> its reset controller. Also, I'd like to understand the memory region >> assigned to bcm7038, which happens to be something like: >> >> compatible = "brcm,bcm7038-wdt"; >> reg = <0xf040a7e8 0x16>; >> >> because it seems unlikely that this is a chip subsystem that just happens >> to start at such an odd boundary. More specifically, I see in actual >> .dtsi files data such as: >> >> watchdog: watchdog@4066a8 { >> clocks = <&upg_clk>; >> compatible = "brcm,bcm7038-wdt"; >> reg = <0x4066a8 0x14>; >> status = "disabled"; >> }; >> ... >> timers: timer@406680 { >> compatible = "brcm,brcmstb-timers"; >> reg = <0x406680 0x40>; >> }; >> >> So there happen to be timers in the same region, and the offset >> between timer and watchdog registers is 0x28. Coincidentally, that >> just happens to be the extra offset defined in this patch for the >> bcm4908 watchdog. Really ? Sorry, this sounds very inconsistent >> and arbitrary to me. > > To Rafal's defense, we could have defined the bcm7038-wdt binding such > that the watchdog would have been at 0x28 from the beginning of the > timer block, but as I wrote earlier, that same watchdog which is really > just 8 bytes worth of register is sometimes instantiated on its own > without the rest of the timer block. This is not visible in a DTS that > is upstream but it does happen in some of the Cable Modem chips. That > was the main motivation for defining the binding the way it was, such > that we could just map those 8 bytes wherever they are. > >> >> Overall, I suspect I'll have to see datasheets if we really end up >> having different offsets for each chip, because I'll want to confirm >> that the watchdog subsystem isn't treated differently than other >> subsystems, and that the offset calculations are appropriate and >> consistent across the different chips. > > Datasheets are not public however sharing the structures documenting the > register layout is something that is possible. For consistency, if we do > let 4908 define the watchdog to include that 0x28 offset, then we are > not mapping just the watchdog, but the entire timer block, which then > raises the question of what happens to the timer interrupt enable/status > and timer registers, how do we end-up sub-dividing that register space > in a logical manner. > I can only see me accepting that if it is consistent across chips. I am perfectly fine with using that offset and including the timer region, but then you'd have to change the code and devicetree files for existing chips as well to be consistent across chips. I can not see that happening. To me it seems that the rules for assigning memory regions in devicetree files are being changed, and the brunt of those changes is pushed into driver code, making it messy (plus, it would create messy devicetree files, some including the offset and some not). I do not think this is a good idea, and I strongly object to it. I don't mind if rules are changed, but please do it for new chips and bindings, chips which require new drivers, not when adding devices to existing bindings. Guenter
On 10/29/21 11:10 AM, Guenter Roeck wrote: > On 10/29/21 10:53 AM, Florian Fainelli wrote: >> On 10/29/21 10:43 AM, Guenter Roeck wrote: >>> On 10/29/21 9:45 AM, Florian Fainelli wrote: >>>> On 10/29/21 6:03 AM, Rob Herring wrote: >>>>> On Fri, Oct 29, 2021 at 01:39:02PM +0200, Rafał Miłecki wrote: >>>>>> [Rob: please kindly comment on this] >>>>>> >>>>>> On 28.10.2021 18:29, Florian Fainelli wrote: >>>>>>> On 10/28/21 2:30 AM, Rafał Miłecki wrote: >>>>>>>> From: Rafał Miłecki <rafal@milecki.pl> >>>>>>>> >>>>>>>> Hardware supported by this driver goes back to the old bcm63xx >>>>>>>> days. It >>>>>>>> was then reused in BCM7038 and later also in BCM4908. >>>>>>>> >>>>>>>> Depending on SoC model registers layout differs a bit. This commit >>>>>>>> introduces support for per-chipset registers offsets & adds BCM4908 >>>>>>>> layout. >>>>>>>> >>>>>>>> Later on BCM63xx SoCs support should be added too (probably as >>>>>>>> platform >>>>>>>> devices due to missing DT). Eventually this driver should replace >>>>>>>> bcm63xx_wdt.c. >>>>>>>> >>>>>>>> Signed-off-by: Rafał Miłecki <rafal@milecki.pl> >>>>>>>> --- >>>>>>> >>>>>>> [snip] >>>>>>> >>>>>>>> + >>>>>>>> +static const u16 bcm7038_wdt_regs_bcm4908[] = { >>>>>>>> + [BCM63XX_WDT_REG_DEFVAL] = 0x28, >>>>>>>> + [BCM63XX_WDT_REG_CTL] = 0x2c, >>>>>>>> + [BCM63XX_WDT_REG_SOFTRESET] = 0x34, >>>>>>> >>>>>>> I don't understand what you are doing here and why you are not >>>>>>> offsetting the "reg" property appropriately when you create your >>>>>>> bcm4908-wdt Device Tree node such that the base starts at 0, and the >>>>>>> existing driver becomes usable as-is. This does not make any sense >>>>>>> to me >>>>>>> when it is obviously the simplest way to make the driver "accept" >>>>>>> the >>>>>>> resource being passed. >>>>>> >>>>>> I believe that DT binding should cover the whole hardware block and >>>>>> describe it (here: use proper compatible to allow recognizing block >>>>>> variant). >>>>>> >>>>>> That's because (as far as I understand) DT should be used to describe >>>>>> hardware as closely as possible. I think it shouldn't be adjusted to >>>>>> make mapping match Linux's driver implementation. >>>>>> >>>>>> >>>>>> So if: >>>>>> 1. Hardware block is mapped at 0xff800400 >>>>>> 2. It has interesting registers at 0xff800428 and 0xff80042c >>>>>> >>>>>> I think mapping should use: >>>>>> reg = <0xff800400 0x3c>; >>>>>> even if we don't use the first N registers. >>>>>> >>>>>> That way, at some point, you can extend Linux (or whatever) driver to >>>>>> use extra registers without reworking the whole binding. That's why I >>>>>> think we need to map whole hardware block & handle different >>>>>> registers >>>>>> layouts in a driver. >>>>> >>>>> Yes, that's the correct thing to do. >>>> >>>> So in the future if we happen to want to manage the hardware timers in >>>> that block, they would be part of the watchdog driver? I am fairly sure >>>> they won't be, so you will be creating a composite driver/MFD to >>>> separate out the functions, more likely. So you might as well create >>>> sub-nodes. >>>> >>>>> >>>>> The question is whether you'd need sub nodes for the other functions. >>>>> Folks tend to want to have sub nodes for convenience which isn't >>>>> really >>>>> needed and then requires a DT update ('cause they add nodes as adding >>>>> drivers). >>>> >>>> Sorry but not, this is getting completely ridiculous, the >>>> >>>>> >>>>> Based on the registers, you really don't need sub nodes here. >>>> >>>> I sort of disagree here, the watchdog is a part of a sundry timer block >>>> here, but it is logically broken up into different parts and if if I >>>> were to imagine how this would map into different drivers, I can easily >>>> see that we would have: >>>> >>>> - a driver to manage the timer interrupt controller >>>> - a driver to manage each of the 3 hardware timers, be they clockevent >>>> or else >>>> - a driver to manage the watchdog >>>> >>>> The simplest way to get there, and also because these same timer blocks >>>> are actually spread in other parts of STB chips just like the watchdog >>>> is, but in a different layout where they stand on their own was the >>>> main >>>> drive for defining the bcm7038_wdt binding the way it was. >>>> >>>> Rafal, I appreciate that you are trying to leverage the bcm7038_wdt >>>> driver and this is better than the previous patch set, but I really do >>>> not see why having the watchdog driver not manage the *exact* subset of >>>> the register space needed (starting at 0x28) is not being done. >>> >>> Agreed, especially since other sub-devices of bcm4908 are alredy modeled >>> this way. See arch/arm64/boot/dts/broadcom/bcm4908/bcm4908.dtsi. >>> At this point, before accepting anything, I'll want to have an >>> explanation >>> how and why the watchdog interface is handled differently than, say, >>> its reset controller. Also, I'd like to understand the memory region >>> assigned to bcm7038, which happens to be something like: >>> >>> compatible = "brcm,bcm7038-wdt"; >>> reg = <0xf040a7e8 0x16>; >>> >>> because it seems unlikely that this is a chip subsystem that just >>> happens >>> to start at such an odd boundary. More specifically, I see in actual >>> .dtsi files data such as: >>> >>> watchdog: watchdog@4066a8 { >>> clocks = <&upg_clk>; >>> compatible = "brcm,bcm7038-wdt"; >>> reg = <0x4066a8 0x14>; >>> status = "disabled"; >>> }; >>> ... >>> timers: timer@406680 { >>> compatible = "brcm,brcmstb-timers"; >>> reg = <0x406680 0x40>; >>> }; >>> >>> So there happen to be timers in the same region, and the offset >>> between timer and watchdog registers is 0x28. Coincidentally, that >>> just happens to be the extra offset defined in this patch for the >>> bcm4908 watchdog. Really ? Sorry, this sounds very inconsistent >>> and arbitrary to me. >> >> To Rafal's defense, we could have defined the bcm7038-wdt binding such >> that the watchdog would have been at 0x28 from the beginning of the >> timer block, but as I wrote earlier, that same watchdog which is really >> just 8 bytes worth of register is sometimes instantiated on its own >> without the rest of the timer block. This is not visible in a DTS that >> is upstream but it does happen in some of the Cable Modem chips. That >> was the main motivation for defining the binding the way it was, such >> that we could just map those 8 bytes wherever they are. >> >>> >>> Overall, I suspect I'll have to see datasheets if we really end up >>> having different offsets for each chip, because I'll want to confirm >>> that the watchdog subsystem isn't treated differently than other >>> subsystems, and that the offset calculations are appropriate and >>> consistent across the different chips. >> >> Datasheets are not public however sharing the structures documenting the >> register layout is something that is possible. For consistency, if we do >> let 4908 define the watchdog to include that 0x28 offset, then we are >> not mapping just the watchdog, but the entire timer block, which then >> raises the question of what happens to the timer interrupt enable/status >> and timer registers, how do we end-up sub-dividing that register space >> in a logical manner. >> > > I can only see me accepting that if it is consistent across chips. > I am perfectly fine with using that offset and including the timer region, > but then you'd have to change the code and devicetree files for existing > chips as well to be consistent across chips. I can not see that happening. > > To me it seems that the rules for assigning memory regions in devicetree > files are being changed, and the brunt of those changes is pushed into > driver code, making it messy (plus, it would create messy devicetree files, > some including the offset and some not). I do not think this is a good > idea, > and I strongly object to it. I don't mind if rules are changed, but please > do it for new chips and bindings, chips which require new drivers, not > when adding devices to existing bindings. Then I believe we are in agreement, the binding is defined the way it is for the bcm7038-wdt such that the "reg" property must be taking the 0x28 offset from the beginning of the timer block into account. Therefore 4908 must conform and do the same thing for consistency. If this is not a good practice, then I will keep that in mind and we will try not to repeat that bad pattern.
On Fri, Oct 29, 2021 at 11:45 AM Florian Fainelli <f.fainelli@gmail.com> wrote: > > On 10/29/21 6:03 AM, Rob Herring wrote: > > On Fri, Oct 29, 2021 at 01:39:02PM +0200, Rafał Miłecki wrote: > >> [Rob: please kindly comment on this] > >> > >> On 28.10.2021 18:29, Florian Fainelli wrote: > >>> On 10/28/21 2:30 AM, Rafał Miłecki wrote: > >>>> From: Rafał Miłecki <rafal@milecki.pl> > >>>> > >>>> Hardware supported by this driver goes back to the old bcm63xx days. It > >>>> was then reused in BCM7038 and later also in BCM4908. > >>>> > >>>> Depending on SoC model registers layout differs a bit. This commit > >>>> introduces support for per-chipset registers offsets & adds BCM4908 > >>>> layout. > >>>> > >>>> Later on BCM63xx SoCs support should be added too (probably as platform > >>>> devices due to missing DT). Eventually this driver should replace > >>>> bcm63xx_wdt.c. > >>>> > >>>> Signed-off-by: Rafał Miłecki <rafal@milecki.pl> > >>>> --- > >>> > >>> [snip] > >>> > >>>> + > >>>> +static const u16 bcm7038_wdt_regs_bcm4908[] = { > >>>> + [BCM63XX_WDT_REG_DEFVAL] = 0x28, > >>>> + [BCM63XX_WDT_REG_CTL] = 0x2c, > >>>> + [BCM63XX_WDT_REG_SOFTRESET] = 0x34, > >>> > >>> I don't understand what you are doing here and why you are not > >>> offsetting the "reg" property appropriately when you create your > >>> bcm4908-wdt Device Tree node such that the base starts at 0, and the > >>> existing driver becomes usable as-is. This does not make any sense to me > >>> when it is obviously the simplest way to make the driver "accept" the > >>> resource being passed. > >> > >> I believe that DT binding should cover the whole hardware block and > >> describe it (here: use proper compatible to allow recognizing block > >> variant). > >> > >> That's because (as far as I understand) DT should be used to describe > >> hardware as closely as possible. I think it shouldn't be adjusted to > >> make mapping match Linux's driver implementation. > >> > >> > >> So if: > >> 1. Hardware block is mapped at 0xff800400 > >> 2. It has interesting registers at 0xff800428 and 0xff80042c > >> > >> I think mapping should use: > >> reg = <0xff800400 0x3c>; > >> even if we don't use the first N registers. > >> > >> That way, at some point, you can extend Linux (or whatever) driver to > >> use extra registers without reworking the whole binding. That's why I > >> think we need to map whole hardware block & handle different registers > >> layouts in a driver. > > > > Yes, that's the correct thing to do. > > So in the future if we happen to want to manage the hardware timers in > that block, they would be part of the watchdog driver? I am fairly sure > they won't be, so you will be creating a composite driver/MFD to > separate out the functions, more likely. So you might as well create > sub-nodes. There is no requirement that an MFD have child nodes. They are done both ways. If you need some internal kernel restructuring, then I don't care (as DT maintainer). We very commonly have a single node that's both clock and reset provider for example. It's primarily when the sub blocks consume different DT resources that you need sub-nodes. > > The question is whether you'd need sub nodes for the other functions. > > Folks tend to want to have sub nodes for convenience which isn't really > > needed and then requires a DT update ('cause they add nodes as adding > > drivers). > > Sorry but not, this is getting completely ridiculous, the Huh? > > > > > Based on the registers, you really don't need sub nodes here. > > I sort of disagree here, the watchdog is a part of a sundry timer block > here, but it is logically broken up into different parts and if if I > were to imagine how this would map into different drivers, I can easily > see that we would have: > > - a driver to manage the timer interrupt controller > - a driver to manage each of the 3 hardware timers, be they clockevent > or else > - a driver to manage the watchdog You know the h/w better than me. I was giving my opinion based only on the limited information presented. > The simplest way to get there, and also because these same timer blocks > are actually spread in other parts of STB chips just like the watchdog > is, but in a different layout where they stand on their own was the main > drive for defining the bcm7038_wdt binding the way it was. A sub-block reused in different blocks is a decent reason for sub-nodes. Most important for me is that the binding be complete and not have to change in an incompatible way in the future. The more detailed you make the binding, the harder it will be to get right. It's the same reason we moved away from doing a clock per node for clock trees. So, if you want child nodes, then you need to define all of them. Rob
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig index bf59faeb3de1..324aa942b182 100644 --- a/drivers/watchdog/Kconfig +++ b/drivers/watchdog/Kconfig @@ -1756,7 +1756,7 @@ config BCM7038_WDT tristate "BCM7038 Watchdog" select WATCHDOG_CORE depends on HAS_IOMEM - depends on ARCH_BRCMSTB || BMIPS_GENERIC || COMPILE_TEST + depends on ARCH_BCM4908 || ARCH_BRCMSTB || BMIPS_GENERIC || COMPILE_TEST help Watchdog driver for the built-in hardware in Broadcom 7038 and later SoCs used in set-top boxes. BCM7038 was made public diff --git a/drivers/watchdog/bcm7038_wdt.c b/drivers/watchdog/bcm7038_wdt.c index acaaa0005d5b..352689f869c1 100644 --- a/drivers/watchdog/bcm7038_wdt.c +++ b/drivers/watchdog/bcm7038_wdt.c @@ -9,6 +9,7 @@ #include <linux/io.h> #include <linux/module.h> #include <linux/of.h> +#include <linux/of_device.h> #include <linux/platform_device.h> #include <linux/pm.h> #include <linux/watchdog.h> @@ -18,14 +19,17 @@ #define WDT_STOP_1 0xee00 #define WDT_STOP_2 0x00ee -#define WDT_TIMEOUT_REG 0x0 -#define WDT_CMD_REG 0x4 - #define WDT_MIN_TIMEOUT 1 /* seconds */ #define WDT_DEFAULT_TIMEOUT 30 /* seconds */ #define WDT_DEFAULT_RATE 27000000 +enum bcm63xx_wdt_soc { + BCM63XX_WDT_SOC_BCM4908, + BCM63XX_WDT_SOC_BCM7038, +}; + struct bcm7038_watchdog { + enum bcm63xx_wdt_soc soc; void __iomem *base; struct watchdog_device wdd; u32 rate; @@ -34,8 +38,52 @@ struct bcm7038_watchdog { static bool nowayout = WATCHDOG_NOWAYOUT; -static inline void bcm7038_wdt_write(u32 value, void __iomem *addr) +static const struct of_device_id bcm7038_wdt_match[] = { + { .compatible = "brcm,bcm4908-wdt", .data = (const void *)BCM63XX_WDT_SOC_BCM4908, }, + { .compatible = "brcm,bcm7038-wdt", .data = (const void *)BCM63XX_WDT_SOC_BCM7038, }, + {}, +}; +MODULE_DEVICE_TABLE(of, bcm7038_wdt_match); + +enum bcm7038_wdt_regs { + BCM63XX_WDT_REG_DEFVAL = 0, + BCM63XX_WDT_REG_CTL, + BCM63XX_WDT_REG_SOFTRESET, +}; + +static const u16 bcm7038_wdt_regs_bcm4908[] = { + [BCM63XX_WDT_REG_DEFVAL] = 0x28, + [BCM63XX_WDT_REG_CTL] = 0x2c, + [BCM63XX_WDT_REG_SOFTRESET] = 0x34, +}; + +static const u16 bcm7038_wdt_regs_bcm7038[] = { + [BCM63XX_WDT_REG_DEFVAL] = 0x00, + [BCM63XX_WDT_REG_CTL] = 0x04, +}; + +static void __iomem *bcm7038_wdt_reg_addr(struct watchdog_device *wdog, + enum bcm7038_wdt_regs reg) { + struct bcm7038_watchdog *wdt = watchdog_get_drvdata(wdog); + void __iomem *addr = wdt->base; + + switch (wdt->soc) { + case BCM63XX_WDT_SOC_BCM4908: + return addr + bcm7038_wdt_regs_bcm4908[reg]; + case BCM63XX_WDT_SOC_BCM7038: + return addr + bcm7038_wdt_regs_bcm7038[reg]; + default: + WARN_ON(1); + return NULL; + } +} + +static void bcm7038_wdt_write(struct watchdog_device *wdog, + enum bcm7038_wdt_regs reg, u32 value) +{ + void __iomem *addr = bcm7038_wdt_reg_addr(wdog, reg); + /* MIPS chips strapped for BE will automagically configure the * peripheral registers for CPU-native byte order. */ @@ -45,8 +93,11 @@ static inline void bcm7038_wdt_write(u32 value, void __iomem *addr) writel_relaxed(value, addr); } -static inline u32 bcm7038_wdt_read(void __iomem *addr) +static inline u32 bcm7038_wdt_read(struct watchdog_device *wdog, + enum bcm7038_wdt_regs reg) { + void __iomem *addr = bcm7038_wdt_reg_addr(wdog, reg); + if (IS_ENABLED(CONFIG_MIPS) && IS_ENABLED(CONFIG_CPU_BIG_ENDIAN)) return __raw_readl(addr); else @@ -60,15 +111,13 @@ static void bcm7038_wdt_set_timeout_reg(struct watchdog_device *wdog) timeout = wdt->rate * wdog->timeout; - bcm7038_wdt_write(timeout, wdt->base + WDT_TIMEOUT_REG); + bcm7038_wdt_write(wdog, BCM63XX_WDT_REG_DEFVAL, timeout); } static int bcm7038_wdt_ping(struct watchdog_device *wdog) { - struct bcm7038_watchdog *wdt = watchdog_get_drvdata(wdog); - - bcm7038_wdt_write(WDT_START_1, wdt->base + WDT_CMD_REG); - bcm7038_wdt_write(WDT_START_2, wdt->base + WDT_CMD_REG); + bcm7038_wdt_write(wdog, BCM63XX_WDT_REG_CTL, WDT_START_1); + bcm7038_wdt_write(wdog, BCM63XX_WDT_REG_CTL, WDT_START_2); return 0; } @@ -83,10 +132,8 @@ static int bcm7038_wdt_start(struct watchdog_device *wdog) static int bcm7038_wdt_stop(struct watchdog_device *wdog) { - struct bcm7038_watchdog *wdt = watchdog_get_drvdata(wdog); - - bcm7038_wdt_write(WDT_STOP_1, wdt->base + WDT_CMD_REG); - bcm7038_wdt_write(WDT_STOP_2, wdt->base + WDT_CMD_REG); + bcm7038_wdt_write(wdog, BCM63XX_WDT_REG_CTL, WDT_STOP_1); + bcm7038_wdt_write(wdog, BCM63XX_WDT_REG_CTL, WDT_STOP_2); return 0; } @@ -107,7 +154,7 @@ static unsigned int bcm7038_wdt_get_timeleft(struct watchdog_device *wdog) struct bcm7038_watchdog *wdt = watchdog_get_drvdata(wdog); u32 time_left; - time_left = bcm7038_wdt_read(wdt->base + WDT_CMD_REG); + time_left = bcm7038_wdt_read(wdog, BCM63XX_WDT_REG_CTL); return time_left / wdt->rate; } @@ -134,6 +181,7 @@ static void bcm7038_clk_disable_unprepare(void *data) static int bcm7038_wdt_probe(struct platform_device *pdev) { struct device *dev = &pdev->dev; + const struct of_device_id *of_id; struct bcm7038_watchdog *wdt; int err; @@ -143,6 +191,11 @@ static int bcm7038_wdt_probe(struct platform_device *pdev) platform_set_drvdata(pdev, wdt); + of_id = of_match_device(bcm7038_wdt_match, dev); + if (!of_id) + return -EINVAL; + wdt->soc = (enum bcm63xx_wdt_soc)of_id->data; + wdt->base = devm_platform_ioremap_resource(pdev, 0); if (IS_ERR(wdt->base)) return PTR_ERR(wdt->base); @@ -211,12 +264,6 @@ static int bcm7038_wdt_resume(struct device *dev) static SIMPLE_DEV_PM_OPS(bcm7038_wdt_pm_ops, bcm7038_wdt_suspend, bcm7038_wdt_resume); -static const struct of_device_id bcm7038_wdt_match[] = { - { .compatible = "brcm,bcm7038-wdt" }, - {}, -}; -MODULE_DEVICE_TABLE(of, bcm7038_wdt_match); - static struct platform_driver bcm7038_wdt_driver = { .probe = bcm7038_wdt_probe, .driver = {