| Message ID | 20221201103651.27807-1-akihiko.odaki@daynix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arch: arm64: dts: apple: Remove stdout-path | expand |
> From: Akihiko Odaki <akihiko.odaki@daynix.com> > Date: Thu, 1 Dec 2022 19:36:51 +0900 > > u-boot overrides stdout-path so that it points to /chosen/framebuffer > with some condition. > > arm: apple: Point stdout-path to framebuffer when keyboard present > > > > Unless you have a spare Apple Silicon machine, getting access to > > the serial port on Apple Silicon machines requires special > > hardware. Given that most machines come with a built-in screen > > the framebuffer is likely to be the most convenient output device > > for most users. While U-Boot will output to both serial and > > framebuffer, OSes might not. Therefore set stdout-path to point > > at /chosen/framebuffer when a keyboard is connected to the machine. > https://github.com/AsahiLinux/u-boot/commit/a609353e82fd757b7635d18ed6a0828fff657d59 > > Perhaps it made sense to specify serial0 as stdout-path when the > framebuffer and keyboard support was inmature, but today it is > preferrable to use /chosen/framebuffer instead of serial0 for the > console in the most cases as the u-boot change states. > > Remove stdout-path to allow the kernel to choose the appropriate > console. For Linux, it will be VT, which will be eventually backed by > the framebuffer, if it is enabled. Otherwise, it will fall back to the > serial. U-Boot still relies on serial being the default. It will not touch stdout-out when running under the m1n1 hypervisor for example. The m1n1 hypervisor emulates the serial port hardware and developers rely on this quite heavily. Also, U-boot will only switch to the framebuffer if a keyboard is connected. This is currently disabled in the builds for Asahi Linux because the type-A USB ports are not supported yet in U-Boot. But the plan is to fix that eventually. So as far as I am concerted NAK. > Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com> > --- > arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi | 2 -- > arch/arm64/boot/dts/apple/t600x-j375.dtsi | 2 -- > arch/arm64/boot/dts/apple/t8103-jxxx.dtsi | 2 -- > arch/arm64/boot/dts/apple/t8112-jxxx.dtsi | 2 -- > 4 files changed, 8 deletions(-) > > diff --git a/arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi b/arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi > index 5547f5e7ac5a..14b6bf234f82 100644 > --- a/arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi > +++ b/arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi > @@ -30,8 +30,6 @@ chosen { > #size-cells = <2>; > ranges; > > - stdout-path = "serial0"; > - > framebuffer0: framebuffer@0 { > compatible = "apple,simple-framebuffer", "simple-framebuffer"; > reg = <0 0 0 0>; /* To be filled by loader */ > diff --git a/arch/arm64/boot/dts/apple/t600x-j375.dtsi b/arch/arm64/boot/dts/apple/t600x-j375.dtsi > index 7c207b1df949..22e96b436bf2 100644 > --- a/arch/arm64/boot/dts/apple/t600x-j375.dtsi > +++ b/arch/arm64/boot/dts/apple/t600x-j375.dtsi > @@ -28,8 +28,6 @@ chosen { > #size-cells = <2>; > ranges; > > - stdout-path = "serial0"; > - > framebuffer0: framebuffer@0 { > compatible = "apple,simple-framebuffer", "simple-framebuffer"; > reg = <0 0 0 0>; /* To be filled by loader */ > diff --git a/arch/arm64/boot/dts/apple/t8103-jxxx.dtsi b/arch/arm64/boot/dts/apple/t8103-jxxx.dtsi > index 3c5da0e5a41d..d2483f618d44 100644 > --- a/arch/arm64/boot/dts/apple/t8103-jxxx.dtsi > +++ b/arch/arm64/boot/dts/apple/t8103-jxxx.dtsi > @@ -27,8 +27,6 @@ chosen { > #size-cells = <2>; > ranges; > > - stdout-path = "serial0"; > - > framebuffer0: framebuffer@0 { > compatible = "apple,simple-framebuffer", "simple-framebuffer"; > reg = <0 0 0 0>; /* To be filled by loader */ > diff --git a/arch/arm64/boot/dts/apple/t8112-jxxx.dtsi b/arch/arm64/boot/dts/apple/t8112-jxxx.dtsi > index b6b815d93c3e..af4153dcb55d 100644 > --- a/arch/arm64/boot/dts/apple/t8112-jxxx.dtsi > +++ b/arch/arm64/boot/dts/apple/t8112-jxxx.dtsi > @@ -22,8 +22,6 @@ chosen { > #size-cells = <2>; > ranges; > > - stdout-path = "serial0"; > - > framebuffer0: framebuffer@0 { > compatible = "apple,simple-framebuffer", "simple-framebuffer"; > reg = <0 0 0 0>; /* To be filled by loader */ > -- > 2.38.1 > > >
On 2022/12/01 23:25, Mark Kettenis wrote: >> From: Akihiko Odaki <akihiko.odaki@daynix.com> >> Date: Thu, 1 Dec 2022 19:36:51 +0900 >> >> u-boot overrides stdout-path so that it points to /chosen/framebuffer >> with some condition. >>> arm: apple: Point stdout-path to framebuffer when keyboard present >>> >>> Unless you have a spare Apple Silicon machine, getting access to >>> the serial port on Apple Silicon machines requires special >>> hardware. Given that most machines come with a built-in screen >>> the framebuffer is likely to be the most convenient output device >>> for most users. While U-Boot will output to both serial and >>> framebuffer, OSes might not. Therefore set stdout-path to point >>> at /chosen/framebuffer when a keyboard is connected to the machine. >> https://github.com/AsahiLinux/u-boot/commit/a609353e82fd757b7635d18ed6a0828fff657d59 >> >> Perhaps it made sense to specify serial0 as stdout-path when the >> framebuffer and keyboard support was inmature, but today it is >> preferrable to use /chosen/framebuffer instead of serial0 for the >> console in the most cases as the u-boot change states. >> >> Remove stdout-path to allow the kernel to choose the appropriate >> console. For Linux, it will be VT, which will be eventually backed by >> the framebuffer, if it is enabled. Otherwise, it will fall back to the >> serial. > > U-Boot still relies on serial being the default. It will not touch > stdout-out when running under the m1n1 hypervisor for example. The > m1n1 hypervisor emulates the serial port hardware and developers rely > on this quite heavily. Also, U-boot will only switch to the > framebuffer if a keyboard is connected. This is currently disabled in > the builds for Asahi Linux because the type-A USB ports are not > supported yet in U-Boot. But the plan is to fix that eventually. > > So as far as I am concerted NAK. Hi, Thanks for reviewing. As far as I know, U-Boot relies on serial being the default only to let the booted kernel use serial when running under the m1n1 hypervisor. It is true that this change regresses the situation in this particular case, but I think it is an exceptional case. m1n1 hypervisor is for development use so we can think of two scenarios: 1. debugging the booted kernel 2. debugging U-Boot For scenario 1, it is unlikely to involve U-Boot because while U-Boot is useful to load the kernel from the disk, the kernel will be usually transferred from another computer during development. In such configuration, m1n1 will directly boots the kernel. For scenario 2, this change should not matter as U-Boot will output to both of serial and framebuffer according to the U-Boot change I mentioned in the previous email. So I think we should think more about the case when the kernel is booted from m1n1. When using its hypervisor feature, it is more likely that you want console on serial and and that is the opposite of this change. However, it is still possible to get the console on framebuffer with keyboard. In contrary, if you boot the kernel without the hypervisor feature and this change, you will completely lose the console. For the USB Type-A port problem, it does not matter if U-Boot supports them because U-Boot will output to both of serial and framebuffer as I mentioned earlier. I think it rather illustrates the situation when this change is useful: for such a configuration, if the booted system can use framebuffer and keyboard, it should, even if U-Boot cannot. I came up with this patch when I stumbled upon your U-Boot change so I appreciate if you tell whether there is something I miss or misunderstand. Regards, Akihiko Odaki > >> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com> >> --- >> arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi | 2 -- >> arch/arm64/boot/dts/apple/t600x-j375.dtsi | 2 -- >> arch/arm64/boot/dts/apple/t8103-jxxx.dtsi | 2 -- >> arch/arm64/boot/dts/apple/t8112-jxxx.dtsi | 2 -- >> 4 files changed, 8 deletions(-) >> >> diff --git a/arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi b/arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi >> index 5547f5e7ac5a..14b6bf234f82 100644 >> --- a/arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi >> +++ b/arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi >> @@ -30,8 +30,6 @@ chosen { >> #size-cells = <2>; >> ranges; >> >> - stdout-path = "serial0"; >> - >> framebuffer0: framebuffer@0 { >> compatible = "apple,simple-framebuffer", "simple-framebuffer"; >> reg = <0 0 0 0>; /* To be filled by loader */ >> diff --git a/arch/arm64/boot/dts/apple/t600x-j375.dtsi b/arch/arm64/boot/dts/apple/t600x-j375.dtsi >> index 7c207b1df949..22e96b436bf2 100644 >> --- a/arch/arm64/boot/dts/apple/t600x-j375.dtsi >> +++ b/arch/arm64/boot/dts/apple/t600x-j375.dtsi >> @@ -28,8 +28,6 @@ chosen { >> #size-cells = <2>; >> ranges; >> >> - stdout-path = "serial0"; >> - >> framebuffer0: framebuffer@0 { >> compatible = "apple,simple-framebuffer", "simple-framebuffer"; >> reg = <0 0 0 0>; /* To be filled by loader */ >> diff --git a/arch/arm64/boot/dts/apple/t8103-jxxx.dtsi b/arch/arm64/boot/dts/apple/t8103-jxxx.dtsi >> index 3c5da0e5a41d..d2483f618d44 100644 >> --- a/arch/arm64/boot/dts/apple/t8103-jxxx.dtsi >> +++ b/arch/arm64/boot/dts/apple/t8103-jxxx.dtsi >> @@ -27,8 +27,6 @@ chosen { >> #size-cells = <2>; >> ranges; >> >> - stdout-path = "serial0"; >> - >> framebuffer0: framebuffer@0 { >> compatible = "apple,simple-framebuffer", "simple-framebuffer"; >> reg = <0 0 0 0>; /* To be filled by loader */ >> diff --git a/arch/arm64/boot/dts/apple/t8112-jxxx.dtsi b/arch/arm64/boot/dts/apple/t8112-jxxx.dtsi >> index b6b815d93c3e..af4153dcb55d 100644 >> --- a/arch/arm64/boot/dts/apple/t8112-jxxx.dtsi >> +++ b/arch/arm64/boot/dts/apple/t8112-jxxx.dtsi >> @@ -22,8 +22,6 @@ chosen { >> #size-cells = <2>; >> ranges; >> >> - stdout-path = "serial0"; >> - >> framebuffer0: framebuffer@0 { >> compatible = "apple,simple-framebuffer", "simple-framebuffer"; >> reg = <0 0 0 0>; /* To be filled by loader */ >> -- >> 2.38.1 >> >> >> >
On 02/12/2022 00.19, Akihiko Odaki wrote: > So I think we should think more about the case when the kernel is booted > from m1n1. When using its hypervisor feature, it is more likely that you > want console on serial and and that is the opposite of this change. > However, it is still possible to get the console on framebuffer with > keyboard. Except if the framebuffer is broken, or everything is broken and it hangs on early boot, which happens all the time when I'm debugging using the hypervisor. Or maybe I'm just SSHing in remotely and not physically in front of the machine, which is also often the case. Or maybe I'm just booting headless because I didn't feel like swapping around the HDMI cable. > In contrary, if you boot the kernel without the hypervisor > feature and this change, you will completely lose the console. How so? The console goes to both places with stdout-path set to serial0. What it *does* change is where input is accepted prior to getty startup (which is why u-boot specifically conditions this on keyboard presence, modulo the USB issue - because if you *don't* have a keyboard then tty keyboard input is useless). But if you're booting kernels without u-boot along the way, you're probably doing it from the hypervisor or linux.py anyway, especially if you plan to do something like "init=/bin/sh", because without u-boot (+ optionally some EFI loader) there is no way of editing command line arguments at boot time stand-alone. However, while having stdout-path gives you both serial + tty output and serial input, *not* having stdout-path kills serial entirely. It also kills earlycon, and makes it so that you have to specify a bunch of obscure arguments to get earlycon to work, instead of just a plain "earlycon" argument which is much easier. So for this to be considered at all, you would first need to propose a m1n1 patch to re-add stdout-path in boots under the hypervisor and (optionally?) on linux.py boots, so you don't regress tools that our developers use every day. But I still fail to see the benefit of this change. What scenario are you envisioning that this would improve (something people actually do, not a hypothetical)? - Hector
Hi, Thank you for reviewing and detailed explanation. I'm withdrawing this patch. As you pointed out it makes earlycon difficult, which is serious in development workflow. As a normal user will use U-Boot, which changes stdout-path if appropriate, this kind of change should be designed to make development easier, and this change does the opposite. On 2022/12/02 0:46, Hector Martin wrote: > On 02/12/2022 00.19, Akihiko Odaki wrote: >> So I think we should think more about the case when the kernel is booted >> from m1n1. When using its hypervisor feature, it is more likely that you >> want console on serial and and that is the opposite of this change. >> However, it is still possible to get the console on framebuffer with >> keyboard. > > Except if the framebuffer is broken, or everything is broken and it > hangs on early boot, which happens all the time when I'm debugging using > the hypervisor. Or maybe I'm just SSHing in remotely and not physically > in front of the machine, which is also often the case. Or maybe I'm just > booting headless because I didn't feel like swapping around the HDMI cable. The user can change the kernel parameter in such a case. If you have already ran the kernel with this change, you should have learned that the console is tied to the framebuffer and keyboard and you need to supply the kernel parameter. It is easy to change the kernel parameter if you use m1n1 directly. > >> In contrary, if you boot the kernel without the hypervisor >> feature and this change, you will completely lose the console. > > How so? The console goes to both places with stdout-path set to serial0. > What it *does* change is where input is accepted prior to getty startup > (which is why u-boot specifically conditions this on keyboard presence, > modulo the USB issue - because if you *don't* have a keyboard then tty > keyboard input is useless). But if you're booting kernels without u-boot > along the way, you're probably doing it from the hypervisor or linux.py > anyway, especially if you plan to do something like "init=/bin/sh", > because without u-boot (+ optionally some EFI loader) there is no way of > editing command line arguments at boot time stand-alone. Well, that is not exactly the behavior I saw. In my case, if stdout-path is pointed to serial, there is no output on the framebuffer, and it just printed "_". It looks like the kernel only outputs to either of serial and framebuffer, not both. > > However, while having stdout-path gives you both serial + tty output and > serial input, *not* having stdout-path kills serial entirely. It also > kills earlycon, and makes it so that you have to specify a bunch of > obscure arguments to get earlycon to work, instead of just a plain > "earlycon" argument which is much easier. This is a valid argument. I always struggle when I try earlycon first for a computer. stdout-path should be maintained if it is freeing developers from such trouble. > > So for this to be considered at all, you would first need to propose a > m1n1 patch to re-add stdout-path in boots under the hypervisor and > (optionally?) on linux.py boots, so you don't regress tools that our > developers use every day. > > But I still fail to see the benefit of this change. What scenario are > you envisioning that this would improve (something people actually do, > not a hypothetical)? > What I experienced is that when I directly booted the kernel from m1n1 without hypervisor, it showed no output to the display even though the same kernel worked with U-Boot. While I could tell it used wrong console by running the hypervisor, I wondered why it behaves differently without U-Boot, and found the aforementioned U-Boot change, coming up with this patch. Regards, Akihiko Odaki > - Hector
On 02/12/2022 01.38, Akihiko Odaki wrote: > >> In contrary, if you boot the kernel without the hypervisor > >> feature and this change, you will completely lose the console. > > > > How so? The console goes to both places with stdout-path set to serial0. > > What it *does* change is where input is accepted prior to getty startup > > (which is why u-boot specifically conditions this on keyboard presence, > > modulo the USB issue - because if you *don't* have a keyboard then tty > > keyboard input is useless). But if you're booting kernels without u-boot > > along the way, you're probably doing it from the hypervisor or linux.py > > anyway, especially if you plan to do something like "init=/bin/sh", > > because without u-boot (+ optionally some EFI loader) there is no way of > > editing command line arguments at boot time stand-alone. > > Well, that is not exactly the behavior I saw. In my case, if stdout-path > is pointed to serial, there is no output on the framebuffer, and it just > printed "_". > > It looks like the kernel only outputs to either of serial and > framebuffer, not both. That is not what I've seen in all of my hypervisor runs since the dawn of time. You get log output on both. > What I experienced is that when I directly booted the kernel from m1n1 > without hypervisor, it showed no output to the display even though the > same kernel worked with U-Boot. While I could tell it used wrong console > by running the hypervisor, I wondered why it behaves differently without > U-Boot, and found the aforementioned U-Boot change, coming up with this > patch. Then it sounds like something else is different about our setups, because I've booted the kernel from linux.py hundreds of times and I get output on both. Looking through the console code, the VT console gets added and enabled really early, and the subsequent serial console registration later does not disable it. Look for "console: colour dummy device 80x25". It should be immediately followed by "printk: console [tty0] enabled", and this should all come well before the ttySAC0 serial stuff shows up. - Hector
On 2022/12/02 2:46, Hector Martin wrote: > On 02/12/2022 01.38, Akihiko Odaki wrote: >> >> In contrary, if you boot the kernel without the hypervisor >> >> feature and this change, you will completely lose the console. >> > >> > How so? The console goes to both places with stdout-path set to serial0. >> > What it *does* change is where input is accepted prior to getty startup >> > (which is why u-boot specifically conditions this on keyboard presence, >> > modulo the USB issue - because if you *don't* have a keyboard then tty >> > keyboard input is useless). But if you're booting kernels without u-boot >> > along the way, you're probably doing it from the hypervisor or linux.py >> > anyway, especially if you plan to do something like "init=/bin/sh", >> > because without u-boot (+ optionally some EFI loader) there is no way of >> > editing command line arguments at boot time stand-alone. >> >> Well, that is not exactly the behavior I saw. In my case, if stdout-path >> is pointed to serial, there is no output on the framebuffer, and it just >> printed "_". >> >> It looks like the kernel only outputs to either of serial and >> framebuffer, not both. > > That is not what I've seen in all of my hypervisor runs since the dawn > of time. You get log output on both. > >> What I experienced is that when I directly booted the kernel from m1n1 >> without hypervisor, it showed no output to the display even though the >> same kernel worked with U-Boot. While I could tell it used wrong console >> by running the hypervisor, I wondered why it behaves differently without >> U-Boot, and found the aforementioned U-Boot change, coming up with this >> patch. > > Then it sounds like something else is different about our setups, > because I've booted the kernel from linux.py hundreds of times and I get > output on both. Looking through the console code, the VT console gets > added and enabled really early, and the subsequent serial console > registration later does not disable it. > > Look for "console: colour dummy device 80x25". It should be immediately > followed by "printk: console [tty0] enabled", and this should all come > well before the ttySAC0 serial stuff shows up. > > - Hector I think I understand the situation now. By "console", I was meaning the input and output of init, but I failed to clarify that and you thought it referring to kernel message output. I saw no messages earlier than init because my kernel command line has loglevel=3. Regards, Akihiko Odaki
diff --git a/arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi b/arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi index 5547f5e7ac5a..14b6bf234f82 100644 --- a/arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi +++ b/arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi @@ -30,8 +30,6 @@ chosen { #size-cells = <2>; ranges; - stdout-path = "serial0"; - framebuffer0: framebuffer@0 { compatible = "apple,simple-framebuffer", "simple-framebuffer"; reg = <0 0 0 0>; /* To be filled by loader */ diff --git a/arch/arm64/boot/dts/apple/t600x-j375.dtsi b/arch/arm64/boot/dts/apple/t600x-j375.dtsi index 7c207b1df949..22e96b436bf2 100644 --- a/arch/arm64/boot/dts/apple/t600x-j375.dtsi +++ b/arch/arm64/boot/dts/apple/t600x-j375.dtsi @@ -28,8 +28,6 @@ chosen { #size-cells = <2>; ranges; - stdout-path = "serial0"; - framebuffer0: framebuffer@0 { compatible = "apple,simple-framebuffer", "simple-framebuffer"; reg = <0 0 0 0>; /* To be filled by loader */ diff --git a/arch/arm64/boot/dts/apple/t8103-jxxx.dtsi b/arch/arm64/boot/dts/apple/t8103-jxxx.dtsi index 3c5da0e5a41d..d2483f618d44 100644 --- a/arch/arm64/boot/dts/apple/t8103-jxxx.dtsi +++ b/arch/arm64/boot/dts/apple/t8103-jxxx.dtsi @@ -27,8 +27,6 @@ chosen { #size-cells = <2>; ranges; - stdout-path = "serial0"; - framebuffer0: framebuffer@0 { compatible = "apple,simple-framebuffer", "simple-framebuffer"; reg = <0 0 0 0>; /* To be filled by loader */ diff --git a/arch/arm64/boot/dts/apple/t8112-jxxx.dtsi b/arch/arm64/boot/dts/apple/t8112-jxxx.dtsi index b6b815d93c3e..af4153dcb55d 100644 --- a/arch/arm64/boot/dts/apple/t8112-jxxx.dtsi +++ b/arch/arm64/boot/dts/apple/t8112-jxxx.dtsi @@ -22,8 +22,6 @@ chosen { #size-cells = <2>; ranges; - stdout-path = "serial0"; - framebuffer0: framebuffer@0 { compatible = "apple,simple-framebuffer", "simple-framebuffer"; reg = <0 0 0 0>; /* To be filled by loader */