| Message ID | 20240613150902.2173582-1-devarsht@ti.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Add global CMA reserve area | expand |
On Thu Jun 13, 2024 at 10:08 AM CDT, Devarsh Thakkar wrote: > Add global CMA reserve area for AM62x, AM62A and AM62P SoCs. > These SoCs do not have MMU and hence require contiguous memory pool to > support various multimedia use-cases. > > Brandon Brnich (1): > arm64: dts: ti: k3-am62p5-sk: Reserve 576 MiB of global CMA > > Devarsh Thakkar (2): > arm64: dts: ti: k3-am62x-sk-common: Reserve 128MiB of global CMA > arm64: dts: ti: k3-am62a7-sk: Reserve 576MiB of global CMA > > arch/arm64/boot/dts/ti/k3-am62a7-sk.dts | 9 +++++++++ > arch/arm64/boot/dts/ti/k3-am62p5-sk.dts | 7 +++++++ > arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi | 8 ++++++++ > 3 files changed, 24 insertions(+) I'm still a little torn about putting this allocation into the device tree directly as the actual required allocation size depends on the task. If it's allowed though, this series is fine for introducing those changes. This uses the long-tested values we've been using on our tree for a bit now. The only thing that's a little worrying is the missing range definitions for devices with more than 32bits of addressable memory as Brandon has pointed out. Once that's addressed: Reviewed-by: Randolph Sapp <rs@ti.com> Specifying these regions using the kernel cmdline parameter via u-boot was brought up as a potential workaround. This is fine until you get into distro boot methods which will almost certainly attempt to override those. I don't know. Still a little odd. Curious how the community feels about it. Technically the user or distro can still override it with the cmdline parameter if necessary, so this may be the best way to have a useful default.
On 6/14/24 12:58 PM, Randolph Sapp wrote: > On Thu Jun 13, 2024 at 10:08 AM CDT, Devarsh Thakkar wrote: >> Add global CMA reserve area for AM62x, AM62A and AM62P SoCs. >> These SoCs do not have MMU and hence require contiguous memory pool to >> support various multimedia use-cases. >> >> Brandon Brnich (1): >> arm64: dts: ti: k3-am62p5-sk: Reserve 576 MiB of global CMA >> >> Devarsh Thakkar (2): >> arm64: dts: ti: k3-am62x-sk-common: Reserve 128MiB of global CMA >> arm64: dts: ti: k3-am62a7-sk: Reserve 576MiB of global CMA >> >> arch/arm64/boot/dts/ti/k3-am62a7-sk.dts | 9 +++++++++ >> arch/arm64/boot/dts/ti/k3-am62p5-sk.dts | 7 +++++++ >> arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi | 8 ++++++++ >> 3 files changed, 24 insertions(+) > > I'm still a little torn about putting this allocation into the device tree > directly as the actual required allocation size depends on the task. > That is the exact reason this does not belong in DT. For everyone *not* using the most extreme case (12x decodes at the same time), this is all wasted space. If one is running out of CMA, they can add more on the kernel cmdline. > If it's allowed though, this series is fine for introducing those changes. This > uses the long-tested values we've been using on our tree for a bit now. The only > thing that's a little worrying is the missing range definitions for devices with > more than 32bits of addressable memory as Brandon has pointed out. Once that's > addressed: > > Reviewed-by: Randolph Sapp <rs@ti.com> > > Specifying these regions using the kernel cmdline parameter via u-boot was > brought up as a potential workaround. This is fine until you get into distro > boot methods which will almost certainly attempt to override those. I don't > know. Still a little odd. Curious how the community feels about it. > > Technically the user or distro can still override it with the cmdline parameter > if necessary, so this may be the best way to have a useful default. > The most useful default is one that doesn't eat 576 MiB of memory "just in case". Needing that much CMA is the exception case and should be the one that requires adding something to the kernel cmdline. If the kernel cmdline option does not work in some cases then we should fix that instead of hard-coding a workaround here in DT. We are robbing ourselves of a better solution here. Andrew
Hi Andrew, Vignesh, On 24/06/24 22:03, Andrew Davis wrote: > On 6/14/24 12:58 PM, Randolph Sapp wrote: >> On Thu Jun 13, 2024 at 10:08 AM CDT, Devarsh Thakkar wrote: >>> Add global CMA reserve area for AM62x, AM62A and AM62P SoCs. >>> These SoCs do not have MMU and hence require contiguous memory pool to >>> support various multimedia use-cases. >>> >>> Brandon Brnich (1): >>> arm64: dts: ti: k3-am62p5-sk: Reserve 576 MiB of global CMA >>> >>> Devarsh Thakkar (2): >>> arm64: dts: ti: k3-am62x-sk-common: Reserve 128MiB of global CMA >>> arm64: dts: ti: k3-am62a7-sk: Reserve 576MiB of global CMA >>> >>> arch/arm64/boot/dts/ti/k3-am62a7-sk.dts | 9 +++++++++ >>> arch/arm64/boot/dts/ti/k3-am62p5-sk.dts | 7 +++++++ >>> arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi | 8 ++++++++ >>> 3 files changed, 24 insertions(+) >> >> I'm still a little torn about putting this allocation into the device tree >> directly as the actual required allocation size depends on the task. >> > > That is the exact reason this does not belong in DT. For everyone *not* > using the most extreme case (12x decodes at the same time), this is > all wasted space. If one is running out of CMA, they can add more on > the kernel cmdline. > I disagree with this. The 12x decode for 480p is not an extreme use-case this is something VPU is capable to run at optimum frame-rate (12x 1080p it can't) and as the AM62A7 is meant to be AI + multimedia centric device, per the device definition we were given the requirements to support a list of multimedia use-cases which should work out of box and 12x decode for 480p was one of them as device is very much capable of doing that with optimum performance and I don't think it is right to change these requirements on the fly. The AM62A7 board has 4 GiB of DDR and we have been using this CMA value since more than a year, I have never heard anyone complain about out of memory or CMA starvation and it suffices to requirements of *most use-cases*, but if for some specific use-case it doesn't suffice, user can change it via kernel cmdline. The kernelcmdline suggestion doesn't suffice out of box experience required, we don't want to ask the user to reboot the board everytime they run out of CMA. >> If it's allowed though, this series is fine for introducing those changes. This >> uses the long-tested values we've been using on our tree for a bit now. The >> only >> thing that's a little worrying is the missing range definitions for devices >> with >> more than 32bits of addressable memory as Brandon has pointed out. Once that's >> addressed: >> >> Reviewed-by: Randolph Sapp <rs@ti.com> >> >> Specifying these regions using the kernel cmdline parameter via u-boot was >> brought up as a potential workaround. This is fine until you get into distro >> boot methods which will almost certainly attempt to override those. I don't >> know. Still a little odd. Curious how the community feels about it. >> >> Technically the user or distro can still override it with the cmdline parameter >> if necessary, so this may be the best way to have a useful default. >> > Unlike above, this solution is independent of distro as it should be as we want that all the supported multimedia use-cases should work out of box. This solution is nothing illegal as CMA region carveouts are not a kernel deprecated feature. > The most useful default is one that doesn't eat 576 MiB of memory "just in case". > Needing that much CMA is the exception case and should be the one that requires > adding something to the kernel cmdline. > I disagree with this, I would have agreed if this point was made in context of generic device, but we are forgetting here that AM62A7 is a AI+multimedia centric device and customers expect multimedia use-cases to work out of box. We have 4 GiB RAM and if carving out 576 MiB is helping achieve all major multimedia use-cases then what's the problem ? What exactly is failing for you ? If some specific scenarios are getting hurt then in that case overlays or kernel cmdline option can be used to override the cma. I feel we are over-complicating things here and going back-and-forth each cycle even though there are no competing alternatives present today. And this blocks out of box experience, as today even the basic HDMI and GPU use-cases don't work out of box. I had also discussed around this with community on last OSS summit as discussed here [1] were it was suggested too to use this solution as adopted by other vendors. [1]: https://lore.kernel.org/all/0eee0424-f177-808f-3a86-499443155ddb@ti.com/ Regards Devarsh
On Fri Jun 28, 2024 at 10:57 AM CDT, Devarsh Thakkar wrote: > Hi Andrew, Vignesh, > > On 24/06/24 22:03, Andrew Davis wrote: > > On 6/14/24 12:58 PM, Randolph Sapp wrote: > >> On Thu Jun 13, 2024 at 10:08 AM CDT, Devarsh Thakkar wrote: > >>> Add global CMA reserve area for AM62x, AM62A and AM62P SoCs. > >>> These SoCs do not have MMU and hence require contiguous memory pool to > >>> support various multimedia use-cases. > >>> > >>> Brandon Brnich (1): > >>> arm64: dts: ti: k3-am62p5-sk: Reserve 576 MiB of global CMA > >>> > >>> Devarsh Thakkar (2): > >>> arm64: dts: ti: k3-am62x-sk-common: Reserve 128MiB of global CMA > >>> arm64: dts: ti: k3-am62a7-sk: Reserve 576MiB of global CMA > >>> > >>> arch/arm64/boot/dts/ti/k3-am62a7-sk.dts | 9 +++++++++ > >>> arch/arm64/boot/dts/ti/k3-am62p5-sk.dts | 7 +++++++ > >>> arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi | 8 ++++++++ > >>> 3 files changed, 24 insertions(+) > >> > >> I'm still a little torn about putting this allocation into the device tree > >> directly as the actual required allocation size depends on the task. > >> > > > > That is the exact reason this does not belong in DT. For everyone *not* > > using the most extreme case (12x decodes at the same time), this is > > all wasted space. If one is running out of CMA, they can add more on > > the kernel cmdline. > > > > I disagree with this. The 12x decode for 480p is not an extreme use-case this > is something VPU is capable to run at optimum frame-rate (12x 1080p it can't) > and as the AM62A7 is meant to be AI + multimedia centric device, per the > device definition we were given the requirements to support a list of > multimedia use-cases which should work out of box and 12x decode for 480p was > one of them as device is very much capable of doing that with optimum > performance and I don't think it is right to change these requirements on the fly. > > The AM62A7 board has 4 GiB of DDR and we have been using this CMA value since > more than a year, I have never heard anyone complain about out of memory or > CMA starvation and it suffices to requirements of *most use-cases*, but if for > some specific use-case it doesn't suffice, user can change it via kernel cmdline. > > The kernelcmdline suggestion doesn't suffice out of box experience required, > we don't want to ask the user to reboot the board everytime they run out of CMA. > > > >> If it's allowed though, this series is fine for introducing those changes. This > >> uses the long-tested values we've been using on our tree for a bit now. The > >> only > >> thing that's a little worrying is the missing range definitions for devices > >> with > >> more than 32bits of addressable memory as Brandon has pointed out. Once that's > >> addressed: > >> > >> Reviewed-by: Randolph Sapp <rs@ti.com> > >> > >> Specifying these regions using the kernel cmdline parameter via u-boot was > >> brought up as a potential workaround. This is fine until you get into distro > >> boot methods which will almost certainly attempt to override those. I don't > >> know. Still a little odd. Curious how the community feels about it. > >> > >> Technically the user or distro can still override it with the cmdline parameter > >> if necessary, so this may be the best way to have a useful default. > >> > > > > Unlike above, this solution is independent of distro as it should be as we > want that all the supported multimedia use-cases should work out of box. This > solution is nothing illegal as CMA region carveouts are not a kernel > deprecated feature. Right. I support this change for at least introducing a usable default. 32M of CMA is barely enough to run glmark2 under Weston once everything's up and running. As I said before, the user or distro can still override the dt CMA block with the cma kernel parameter if they aren't happy with the default block. Unfortunately this is about the only way to have a usable default value to fall back on. > > The most useful default is one that doesn't eat 576 MiB of memory "just in case". > > Needing that much CMA is the exception case and should be the one that requires > > adding something to the kernel cmdline. > > > > I disagree with this, I would have agreed if this point was made in context of > generic device, but we are forgetting here that AM62A7 is a AI+multimedia > centric device and customers expect multimedia use-cases to work out of box. > > We have 4 GiB RAM and if carving out 576 MiB is helping achieve all major > multimedia use-cases then what's the problem ? What exactly is failing for you > ? If some specific scenarios are getting hurt then in that case overlays or > kernel cmdline option can be used to override the cma. > > I feel we are over-complicating things here and going back-and-forth each > cycle even though there are no competing alternatives present today. > And this blocks out of box experience, as today even the basic HDMI and GPU > use-cases don't work out of box. > > I had also discussed around this with community on last OSS summit as > discussed here [1] were it was suggested too to use this solution as adopted > by other vendors. > > [1]: https://lore.kernel.org/all/0eee0424-f177-808f-3a86-499443155ddb@ti.com/ > > Regards > Devarsh If the community accepts it, it's fine by me. - Randolph
On 28/06/24 22:05, Randolph Sapp wrote: > On Fri Jun 28, 2024 at 10:57 AM CDT, Devarsh Thakkar wrote: >> Hi Andrew, Vignesh, >> >> On 24/06/24 22:03, Andrew Davis wrote: >>> On 6/14/24 12:58 PM, Randolph Sapp wrote: >>>> On Thu Jun 13, 2024 at 10:08 AM CDT, Devarsh Thakkar wrote: >>>>> Add global CMA reserve area for AM62x, AM62A and AM62P SoCs. >>>>> These SoCs do not have MMU and hence require contiguous memory pool to >>>>> support various multimedia use-cases. >>>>> >>>>> Brandon Brnich (1): >>>>> arm64: dts: ti: k3-am62p5-sk: Reserve 576 MiB of global CMA >>>>> >>>>> Devarsh Thakkar (2): >>>>> arm64: dts: ti: k3-am62x-sk-common: Reserve 128MiB of global CMA >>>>> arm64: dts: ti: k3-am62a7-sk: Reserve 576MiB of global CMA >>>>> >>>>> arch/arm64/boot/dts/ti/k3-am62a7-sk.dts | 9 +++++++++ >>>>> arch/arm64/boot/dts/ti/k3-am62p5-sk.dts | 7 +++++++ >>>>> arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi | 8 ++++++++ >>>>> 3 files changed, 24 insertions(+) >>>> >>>> I'm still a little torn about putting this allocation into the device tree >>>> directly as the actual required allocation size depends on the task. >>>> >>> >>> That is the exact reason this does not belong in DT. For everyone *not* >>> using the most extreme case (12x decodes at the same time), this is >>> all wasted space. If one is running out of CMA, they can add more on >>> the kernel cmdline. >>> >> >> I disagree with this. The 12x decode for 480p is not an extreme use-case this >> is something VPU is capable to run at optimum frame-rate (12x 1080p it can't) >> and as the AM62A7 is meant to be AI + multimedia centric device, per the >> device definition we were given the requirements to support a list of >> multimedia use-cases which should work out of box and 12x decode for 480p was >> one of them as device is very much capable of doing that with optimum >> performance and I don't think it is right to change these requirements on the fly. >> >> The AM62A7 board has 4 GiB of DDR and we have been using this CMA value since >> more than a year, I have never heard anyone complain about out of memory or >> CMA starvation and it suffices to requirements of *most use-cases*, but if for >> some specific use-case it doesn't suffice, user can change it via kernel cmdline. >> >> The kernelcmdline suggestion doesn't suffice out of box experience required, >> we don't want to ask the user to reboot the board everytime they run out of CMA. >> >> >>>> If it's allowed though, this series is fine for introducing those changes. This >>>> uses the long-tested values we've been using on our tree for a bit now. The >>>> only >>>> thing that's a little worrying is the missing range definitions for devices >>>> with >>>> more than 32bits of addressable memory as Brandon has pointed out. Once that's >>>> addressed: >>>> >>>> Reviewed-by: Randolph Sapp <rs@ti.com> >>>> >>>> Specifying these regions using the kernel cmdline parameter via u-boot was >>>> brought up as a potential workaround. This is fine until you get into distro >>>> boot methods which will almost certainly attempt to override those. I don't >>>> know. Still a little odd. Curious how the community feels about it. >>>> >>>> Technically the user or distro can still override it with the cmdline parameter >>>> if necessary, so this may be the best way to have a useful default. >>>> >>> >> >> Unlike above, this solution is independent of distro as it should be as we >> want that all the supported multimedia use-cases should work out of box. This >> solution is nothing illegal as CMA region carveouts are not a kernel >> deprecated feature. > > Right. I support this change for at least introducing a usable default. 32M of > CMA is barely enough to run glmark2 under Weston once everything's up and > running. > > As I said before, the user or distro can still override the dt CMA block with > the cma kernel parameter if they aren't happy with the default block. > Unfortunately this is about the only way to have a usable default value to fall > back on. > Given the number of SoMs and non TI EVMs that are about to come out with AM62A/P and AM67s, we need to provide a consistent way of being able to support multimedia IPs out of the box. Modifying cmdline may not always be feasible given distro defaults don't always provide a way to do so. So I am inclined to queue first 2 patches unless there is another way t achieve this. [...]
On 6/30/24 2:09 AM, Vignesh Raghavendra wrote: > > > On 28/06/24 22:05, Randolph Sapp wrote: >> On Fri Jun 28, 2024 at 10:57 AM CDT, Devarsh Thakkar wrote: >>> Hi Andrew, Vignesh, >>> >>> On 24/06/24 22:03, Andrew Davis wrote: >>>> On 6/14/24 12:58 PM, Randolph Sapp wrote: >>>>> On Thu Jun 13, 2024 at 10:08 AM CDT, Devarsh Thakkar wrote: >>>>>> Add global CMA reserve area for AM62x, AM62A and AM62P SoCs. >>>>>> These SoCs do not have MMU and hence require contiguous memory pool to >>>>>> support various multimedia use-cases. >>>>>> >>>>>> Brandon Brnich (1): >>>>>> arm64: dts: ti: k3-am62p5-sk: Reserve 576 MiB of global CMA >>>>>> >>>>>> Devarsh Thakkar (2): >>>>>> arm64: dts: ti: k3-am62x-sk-common: Reserve 128MiB of global CMA >>>>>> arm64: dts: ti: k3-am62a7-sk: Reserve 576MiB of global CMA >>>>>> >>>>>> arch/arm64/boot/dts/ti/k3-am62a7-sk.dts | 9 +++++++++ >>>>>> arch/arm64/boot/dts/ti/k3-am62p5-sk.dts | 7 +++++++ >>>>>> arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi | 8 ++++++++ >>>>>> 3 files changed, 24 insertions(+) >>>>> >>>>> I'm still a little torn about putting this allocation into the device tree >>>>> directly as the actual required allocation size depends on the task. >>>>> >>>> >>>> That is the exact reason this does not belong in DT. For everyone *not* >>>> using the most extreme case (12x decodes at the same time), this is >>>> all wasted space. If one is running out of CMA, they can add more on >>>> the kernel cmdline. >>>> >>> >>> I disagree with this. The 12x decode for 480p is not an extreme use-case this >>> is something VPU is capable to run at optimum frame-rate (12x 1080p it can't) >>> and as the AM62A7 is meant to be AI + multimedia centric device, per the >>> device definition we were given the requirements to support a list of >>> multimedia use-cases which should work out of box and 12x decode for 480p was >>> one of them as device is very much capable of doing that with optimum >>> performance and I don't think it is right to change these requirements on the fly. >>> >>> The AM62A7 board has 4 GiB of DDR and we have been using this CMA value since >>> more than a year, I have never heard anyone complain about out of memory or >>> CMA starvation and it suffices to requirements of *most use-cases*, but if for >>> some specific use-case it doesn't suffice, user can change it via kernel cmdline. >>> >>> The kernelcmdline suggestion doesn't suffice out of box experience required, >>> we don't want to ask the user to reboot the board everytime they run out of CMA. >>> >>> >>>>> If it's allowed though, this series is fine for introducing those changes. This >>>>> uses the long-tested values we've been using on our tree for a bit now. The >>>>> only >>>>> thing that's a little worrying is the missing range definitions for devices >>>>> with >>>>> more than 32bits of addressable memory as Brandon has pointed out. Once that's >>>>> addressed: >>>>> >>>>> Reviewed-by: Randolph Sapp <rs@ti.com> >>>>> >>>>> Specifying these regions using the kernel cmdline parameter via u-boot was >>>>> brought up as a potential workaround. This is fine until you get into distro >>>>> boot methods which will almost certainly attempt to override those. I don't >>>>> know. Still a little odd. Curious how the community feels about it. >>>>> >>>>> Technically the user or distro can still override it with the cmdline parameter >>>>> if necessary, so this may be the best way to have a useful default. >>>>> >>>> >>> >>> Unlike above, this solution is independent of distro as it should be as we >>> want that all the supported multimedia use-cases should work out of box. This >>> solution is nothing illegal as CMA region carveouts are not a kernel >>> deprecated feature. >> >> Right. I support this change for at least introducing a usable default. 32M of >> CMA is barely enough to run glmark2 under Weston once everything's up and >> running. >> >> As I said before, the user or distro can still override the dt CMA block with >> the cma kernel parameter if they aren't happy with the default block. >> Unfortunately this is about the only way to have a usable default value to fall >> back on. >> > > > Given the number of SoMs and non TI EVMs that are about to come out with > AM62A/P and AM67s, we need to provide a consistent way of being able to > support multimedia IPs out of the box. Modifying cmdline may not always > be feasible given distro defaults don't always provide a way to do so. > We need to keep thinking then. I empathize with desire to put configuration in Device Tree. DT feels like a great spot for it, it is ubiquitous on these boards and has a good bit of tooling around it. We are already describing the hardware, why not configure it here too? But the reason we do not want to go down that road is simple: DT takes away use-case flexibility. A lack of flexibility is fine for hardware which is unchanging, but not for configuration. Device policy and configuration must be left to userspace. It is not for us to decide how folks should use our hardware, and that is what we are doing when we configure it in DT. For configuration that must happen in early boot before userspace is available (such as kernel stdout and memory carveouts) we have the kernel cmdline. If we find something that cannot be done today though the cmdline, then we should add that support to the cmdline, not give up and just hide the configuration in DT. What this series does is already available on the kernel cmdline. Our bootloader can provide sane defaults on the cmdline today. If the worry is that distros will override this default then go fix those distros. > So I am inclined to queue first 2 patches unless there is another way t > achieve this. > Our lack of creativity in finding better solutions to this issue is not an excuse to add more junk to DT.. Andrew > [...] >
On Mon Jul 1, 2024 at 9:33 AM CDT, Andrew Davis wrote: > On 6/30/24 2:09 AM, Vignesh Raghavendra wrote: > > > > > > On 28/06/24 22:05, Randolph Sapp wrote: > >> On Fri Jun 28, 2024 at 10:57 AM CDT, Devarsh Thakkar wrote: > >>> Hi Andrew, Vignesh, > >>> > >>> On 24/06/24 22:03, Andrew Davis wrote: > >>>> On 6/14/24 12:58 PM, Randolph Sapp wrote: > >>>>> On Thu Jun 13, 2024 at 10:08 AM CDT, Devarsh Thakkar wrote: > >>>>>> Add global CMA reserve area for AM62x, AM62A and AM62P SoCs. > >>>>>> These SoCs do not have MMU and hence require contiguous memory pool to > >>>>>> support various multimedia use-cases. > >>>>>> > >>>>>> Brandon Brnich (1): > >>>>>> arm64: dts: ti: k3-am62p5-sk: Reserve 576 MiB of global CMA > >>>>>> > >>>>>> Devarsh Thakkar (2): > >>>>>> arm64: dts: ti: k3-am62x-sk-common: Reserve 128MiB of global CMA > >>>>>> arm64: dts: ti: k3-am62a7-sk: Reserve 576MiB of global CMA > >>>>>> > >>>>>> arch/arm64/boot/dts/ti/k3-am62a7-sk.dts | 9 +++++++++ > >>>>>> arch/arm64/boot/dts/ti/k3-am62p5-sk.dts | 7 +++++++ > >>>>>> arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi | 8 ++++++++ > >>>>>> 3 files changed, 24 insertions(+) > >>>>> > >>>>> I'm still a little torn about putting this allocation into the device tree > >>>>> directly as the actual required allocation size depends on the task. > >>>>> > >>>> > >>>> That is the exact reason this does not belong in DT. For everyone *not* > >>>> using the most extreme case (12x decodes at the same time), this is > >>>> all wasted space. If one is running out of CMA, they can add more on > >>>> the kernel cmdline. > >>>> > >>> > >>> I disagree with this. The 12x decode for 480p is not an extreme use-case this > >>> is something VPU is capable to run at optimum frame-rate (12x 1080p it can't) > >>> and as the AM62A7 is meant to be AI + multimedia centric device, per the > >>> device definition we were given the requirements to support a list of > >>> multimedia use-cases which should work out of box and 12x decode for 480p was > >>> one of them as device is very much capable of doing that with optimum > >>> performance and I don't think it is right to change these requirements on the fly. > >>> > >>> The AM62A7 board has 4 GiB of DDR and we have been using this CMA value since > >>> more than a year, I have never heard anyone complain about out of memory or > >>> CMA starvation and it suffices to requirements of *most use-cases*, but if for > >>> some specific use-case it doesn't suffice, user can change it via kernel cmdline. > >>> > >>> The kernelcmdline suggestion doesn't suffice out of box experience required, > >>> we don't want to ask the user to reboot the board everytime they run out of CMA. > >>> > >>> > >>>>> If it's allowed though, this series is fine for introducing those changes. This > >>>>> uses the long-tested values we've been using on our tree for a bit now. The > >>>>> only > >>>>> thing that's a little worrying is the missing range definitions for devices > >>>>> with > >>>>> more than 32bits of addressable memory as Brandon has pointed out. Once that's > >>>>> addressed: > >>>>> > >>>>> Reviewed-by: Randolph Sapp <rs@ti.com> > >>>>> > >>>>> Specifying these regions using the kernel cmdline parameter via u-boot was > >>>>> brought up as a potential workaround. This is fine until you get into distro > >>>>> boot methods which will almost certainly attempt to override those. I don't > >>>>> know. Still a little odd. Curious how the community feels about it. > >>>>> > >>>>> Technically the user or distro can still override it with the cmdline parameter > >>>>> if necessary, so this may be the best way to have a useful default. > >>>>> > >>>> > >>> > >>> Unlike above, this solution is independent of distro as it should be as we > >>> want that all the supported multimedia use-cases should work out of box. This > >>> solution is nothing illegal as CMA region carveouts are not a kernel > >>> deprecated feature. > >> > >> Right. I support this change for at least introducing a usable default. 32M of > >> CMA is barely enough to run glmark2 under Weston once everything's up and > >> running. > >> > >> As I said before, the user or distro can still override the dt CMA block with > >> the cma kernel parameter if they aren't happy with the default block. > >> Unfortunately this is about the only way to have a usable default value to fall > >> back on. > >> > > > > > > Given the number of SoMs and non TI EVMs that are about to come out with > > AM62A/P and AM67s, we need to provide a consistent way of being able to > > support multimedia IPs out of the box. Modifying cmdline may not always > > be feasible given distro defaults don't always provide a way to do so. > > > > We need to keep thinking then. I empathize with desire to put > configuration in Device Tree. DT feels like a great spot for it, > it is ubiquitous on these boards and has a good bit of tooling around > it. We are already describing the hardware, why not configure it here > too? But the reason we do not want to go down that road is simple: > DT takes away use-case flexibility. A lack of flexibility is fine for > hardware which is unchanging, but not for configuration. I agree with the sentiment here, but this explicit case is an exception. This is no more than a default value. Userspace can still change this allocation with the kernel cma parameter. That still takes precedence. > Device policy and configuration must be left to userspace. > > It is not for us to decide how folks should use our hardware, and > that is what we are doing when we configure it in DT. > > For configuration that must happen in early boot before userspace is > available (such as kernel stdout and memory carveouts) we have the > kernel cmdline. If we find something that cannot be done today though > the cmdline, then we should add that support to the cmdline, not > give up and just hide the configuration in DT. > > What this series does is already available on the kernel cmdline. > Our bootloader can provide sane defaults on the cmdline today. > If the worry is that distros will override this default then > go fix those distros. Our bootloaders doing anything to kernel cmdline parameters is inherently non-standard. You just brought up userspace control. They clobber cmdline parameters all the time. Unsetting this bootloader value will be the first thing they do. This will be done passively, since they normally inject a new intermediary boot stage that they can actually control between u-boot and their kernel. - Randolph > > So I am inclined to queue first 2 patches unless there is another way t > > achieve this. > > > > Our lack of creativity in finding better solutions to this issue is > not an excuse to add more junk to DT.. > > Andrew > > > [...] > >
Hi Devarsh Thakkar, On Thu, 13 Jun 2024 20:38:59 +0530, Devarsh Thakkar wrote: > Add global CMA reserve area for AM62x, AM62A and AM62P SoCs. > These SoCs do not have MMU and hence require contiguous memory pool to > support various multimedia use-cases. > > Brandon Brnich (1): > arm64: dts: ti: k3-am62p5-sk: Reserve 576 MiB of global CMA > > [...] I have applied the following to branch ti-k3-dts-next on [1]. Thank you! [1/3] arm64: dts: ti: k3-am62x-sk-common: Reserve 128MiB of global CMA commit: 9e8560556f9c41da28118af3385b4e9dc832ae2b [2/3] arm64: dts: ti: k3-am62a7-sk: Reserve 576MiB of global CMA commit: 6406c5d5512c0814b8c155df7f833a98d9069a72 All being well this means that it will be integrated into the linux-next tree (usually sometime in the next 24 hours) and sent up the chain during the next merge window (or sooner if it is a relevant bug fix), however if problems are discovered then the patch may be dropped or reverted. You may get further e-mails resulting from automated or manual testing and review of the tree, please engage with people reporting problems and send followup patches addressing any issues that are reported if needed. If any updates are required or you are submitting further changes they should be sent as incremental updates against current git, existing patches will not be replaced. Please add any relevant lists and maintainers to the CCs when replying to this mail. [1] https://git.kernel.org/pub/scm/linux/kernel/git/ti/linux.git -- Vignesh