Raspberry Pi 3 Model B+ hangs in vc4_hdmi_runtime_resume()

Tue Sep 27 11:47:54 PDT 2022

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On Tue, Sep 27, 2022 at 8:46 PM Stefan Wahren <stefan.wahren at i2se.com> wrote:
>
> Hi Maxime,
>
> Am 27.09.22 um 15:15 schrieb Maxime Ripard:
> > On Tue, Sep 27, 2022 at 02:25:12PM +0200, Maxime Ripard wrote:
> >> On Tue, Sep 27, 2022 at 01:42:40PM +0200, Maxime Ripard wrote:
> >>> On Tue, Sep 27, 2022 at 01:12:35PM +0200, Stefan Wahren wrote:
> >>>> Am 27.09.22 um 11:42 schrieb Maxime Ripard:
> >>>>> On Tue, Sep 27, 2022 at 09:25:54AM +0200, Maxime Ripard wrote:
> >>>>>> Hi Stefan,
> >>>>>>
> >>>>>> On Mon, Sep 26, 2022 at 08:50:12PM +0200, Stefan Wahren wrote:
> >>>>>>> Am 26.09.22 um 14:47 schrieb Maxime Ripard:
> >>>>>>>> On Mon, Sep 26, 2022 at 02:40:48PM +0200, Marc Kleine-Budde wrote:
> >>>>>>>>> On 26.09.2022 14:08:04, Stefan Wahren wrote:
> >>>>>>>>>> Hi Marc,
> >>>>>>>>>>
> >>>>>>>>>> Am 26.09.22 um 12:21 schrieb Marc Kleine-Budde:
> >>>>>>>>>>> On 22.09.2022 17:06:00, Maxime Ripard wrote:
> >>>>>>>>>>>>> I'm on a Raspberry Pi 3 Model B+ running current Debian testing ARM64,
> >>>>>>>>>>>>> using Debian's v5.19 kernel (Debian's v5.18 was working flawless).
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> | [    0.000000] Booting Linux on physical CPU 0x0000000000 [0x410fd034]
> >>>>>>>>>>>>> | [    0.000000] Linux version 5.19.0-1-arm64 (debian-kernel at lists.debian.org) (gcc-11 (Debian 11.3.0-5) 11.3.0, GNU ld (GNU Binutils for Debian) 2.38.90.20220713) #1 SMP Debian 5.19.6-1 (2022-0
> >>>>>>>>>>>>> 9-01)
> >>>>>>>>>>>>> | [    0.000000] Machine model: Raspberry Pi 3 Model B+
> >>>>>>>>>>>>> | [    3.747500] raspberrypi-firmware soc:firmware: Attached to firmware from 2022-03-24T13:21:11
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> As soon a the vc4 module is loaded the following warnings hits 4
> >>>>>>>>>>>>> times, then the machine stops.
> >>>>>>>>>>> [...]
> >>>>>>>>>>>
> >>>>>>>>>>>> The warning itself is fixed, both upstream and in stable (5.19.7).
> >>>>>>>>>>> Ok. Debian is using 5.19.6
> >>>>>>>>>>>
> >>>>>>>>>>>> It shouldn't have any relation to the hang though. Can you share your
> >>>>>>>>>>>> setup?
> >>>>>>>>>>> - config.txt:
> >>>>>>>>>>>
> >>>>>>>>>>> -------->8-------->8-------->8-------->8--------
> >>>>>>>>>>> gpu_mem=16
> >>>>>>>>>>> disable_splash=1
> >>>>>>>>>>>
> >>>>>>>>>>> arm_64bit=1
> >>>>>>>>>>> enable_uart=1
> >>>>>>>>>>> uart_2ndstage=1
> >>>>>>>>>>>
> >>>>>>>>>>> os_prefix=/u-boot/
> >>>>>>>>>>>
> >>>>>>>>>>> [pi3]
> >>>>>>>>>>> force_turbo=1
> >>>>>>>>>>> -------->8-------->8-------->8-------->8--------
> >>>>>>>>>>>
> >>>>>>>>>>> - Raspberry Pi 3 Model B+
> >>>>>>>>>>> - no HDMI connected
> >>>>>>>>>> Does it mean, the issue only occurs without HDMI connected?
> >>>>>>>>>> If you didn't test with HDMI yet, could you please do?
> >>>>>>>>> The error occurs with HDMI not connected, as vc4 is the gfx driver I
> >>>>>>>>> thought this might be of interest. :)
> >>>>>>>>>
> >>>>>>>>> I don't have a HDMI monitor here, but I'll come back to you as soon as I
> >>>>>>>>> get access to one (might take some time).
> >>>>>>>> It's not the first time an issue like this one would occur. I'm trying
> >>>>>>>> to make my Pi3 boot again, and will try to bisect the issue.
> >>>>>>> yes the issue is only triggered without HDMI connected. I was able to
> >>>>>>> reproduce with an older vc4 firmware from 2020 (don't want to upgrade yet).
> >>>>>>> Kernel was also an arm64 build with defconfig.
> >>>>>>>
> >>>>>>> Here some rough starting point for bisection:
> >>>>>>>
> >>>>>>> 5.18.0 good
> >>>>>>> 5.19.0 bad
> >>>>>>> 5.19.6 bad
> >>>>>> Sorry it took a bit of time, it looks like I found another bug while
> >>>>>> trying to test this yesterday.
> >>>>>>
> >>>>>> Your datapoints are interesting though. I have a custom configuration
> >>>>>> and it does boot 5.19 without an HDMI connected.
> >>>>>>
> >>>>>> So I guess it leaves us with either the firmware version being different
> >>>>>> (I'm using a newer version, from March 2022), or the configuration. I'll
> >>>>>> test with defconfig.
> >>>>> So it turns out compiling vc4 as a module is the culprit.
> >>>> Do you mean regardless of the kernel version in your case?
> >>> No, I mean that, with vc4 as a module, 5.18 works but 5.19 doesn't, like
> >>> Marc said. But if vc4 is built in, both work.
> >>>
> >>>> In my test cases i build vc4 always as module.
> >>>>
> >>>>> It's not clear to me why at this point, but the first register write in
> >>>>> vc4_hdmi_reset stalls.
> >>>> Sounds like timing issue or a missing dependency (clock or power domain)
> >>> It felt like a clock or power domain issue to me indeed, but adding
> >>> clk_ignore_unused and pd_ignore_unused isn't enough, so it's probably
> >>> something a bit more complicated than just the clock / PD being
> >>> disabled.
> >> I found the offending patch:
> >> https://lore.kernel.org/dri-devel/20220225143534.405820-13-maxime@cerno.tech/
> >>
> >> That code was removed because it was made irrelevant by that earlier patch:
> >> https://lore.kernel.org/dri-devel/20220225143534.405820-10-maxime@cerno.tech/
> >>
> >> But it turns out that while it works when the driver is built-in, it
> >> doesn't when it's a module. If we add a clk_hw_get_rate() call right
> >> after that call to raspberrypi_fw_set_rate(), the rate returned is 0.
> >>
> >> I'm not entirely sure why, but I wonder if it's related to:
> >> https://github.com/raspberrypi/linux/issues/4962#issuecomment-1228593439
> > Turns out it's not, since the Pi3 is using the clk-bcm2835 driver.
>
> FWIW i can confirm, that i see the same behavior:
>
> fd5894fa2413cca3e6a3ea713b2bd57281af2e86 bad
>
> 5b6ef06ea6225570bc0b33325306c7b8c6bdf5eb good
>
> >
> > However, even reverting that patch fails. clk_set_min_rate fails because
> > the rate is protected, but it doesn't look like it is anywhere for that
> > clock, so I'm a bit confused.
> >
> > Even if we do remove the clock protection check in
> > clk_core_set_rate_nolock(), clk_calc_new_rates() will then fail because
> > the bcm2835 driver will round the clock rate below the minimum, which is
> > rejected.
> >
> > I'm not entirely sure what to do at this point. I guess the proper fix
> > would be to:
> >    - Figure out why it's considered protected when it's not (or shouldn't be)
> >    - Make the driver compute an acceptable rate for that clock
> >    - Reintroduce the clk_set_min_rate call to HDMI's runtime_resume, or
> >      some other equivalent code
> >
> > Maxime
>
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