Re: [PATCH] drm/panfrost: fix power transition timeout warnings

[AngeloGioacchino Del Regno]

Il 25/03/24 12:36, Christian Hewitt ha scritto:
> > On 25 Mar 2024, at 2:28 pm, Steven Price <steven.price@xxxxxxx> wrote:
> >
> > On 22/03/2024 16:45, Christian Hewitt wrote:
> > > Increase the timeout value to prevent system logs on Amlogic boards flooding
> > > with power transition warnings:
> > >
> > > [   13.047638] panfrost ffe40000.gpu: shader power transition timeout
> > > [   13.048674] panfrost ffe40000.gpu: l2 power transition timeout
> > > [   13.937324] panfrost ffe40000.gpu: shader power transition timeout
> > > [   13.938351] panfrost ffe40000.gpu: l2 power transition timeout
> > > ...
> > > [39829.506904] panfrost ffe40000.gpu: shader power transition timeout
> > > [39829.507938] panfrost ffe40000.gpu: l2 power transition timeout
> > > [39949.508369] panfrost ffe40000.gpu: shader power transition timeout
> > > [39949.509405] panfrost ffe40000.gpu: l2 power transition timeout
> > >
> > > The 2000 value has been found through trial and error testing with devices
> > > using G52 and G31 GPUs.
> >
> > How close to 2ms did you need in your trial and error testing? I'm
> > wondering if we should increase it further in case this might still
> > trigger occasionally?
>
> I backed it off progressively but still saw occasional messages at 1.6ms
> so padded it a little with 2ms, and those systems haven’t shown errors
> since so I currently see it as a ’safe’ value. The one possible wildcard
> is testing with older T820/T628 boards; but that needs to wait until I’m
> back home from a long trip and able to test them. The possible theory
> being that older/slower systems might require more time. Worst case I’ll
> have to send another change.
>
> > kbase seems to have a 5s (5000ms!) timeout before it will actually
> > complain. But equally it doesn't busy wait on the registers in the same
> > way as panfrost, so the impact to the rest of the system of a long wait
> > is less.
> >
> > But 2ms doesn't sound an unreasonable timeout so:
> >
> > Reviewed-by: Steven Price <steven.price@xxxxxxx>
> >
> > > Fixes: 22aa1a209018 ("drm/panfrost: Really power off GPU cores in panfrost_gpu_power_off()")
> > > Signed-off-by: Christian Hewitt <christianshewitt@xxxxxxxxx>> ---
> > > drivers/gpu/drm/panfrost/panfrost_gpu.c | 6 +++---
> > > 1 file changed, 3 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/panfrost/panfrost_gpu.c b/drivers/gpu/drm/panfrost/panfrost_gpu.c
> > > index 9063ce254642..fd8e44992184 100644
> > > --- a/drivers/gpu/drm/panfrost/panfrost_gpu.c
> > > +++ b/drivers/gpu/drm/panfrost/panfrost_gpu.c
> > > @@ -441,19 +441,19 @@ void panfrost_gpu_power_off(struct panfrost_device *pfdev)
> > >
> > > gpu_write(pfdev, SHADER_PWROFF_LO, pfdev->features.shader_present);
> > > ret = readl_relaxed_poll_timeout(pfdev->iomem + SHADER_PWRTRANS_LO,
> > > -  val, !val, 1, 1000);
> > > +  val, !val, 1, 2000);
> > > if (ret)
> > > dev_err(pfdev->dev, "shader power transition timeout");
> > >
> > > gpu_write(pfdev, TILER_PWROFF_LO, pfdev->features.tiler_present);
> > > ret = readl_relaxed_poll_timeout(pfdev->iomem + TILER_PWRTRANS_LO,
> > > -  val, !val, 1, 1000);
> > > +  val, !val, 1, 2000);
> > > if (ret)
> > > dev_err(pfdev->dev, "tiler power transition timeout");
> >
> > As Angelo points out the tiler probably doesn't need such a long
> > timeout, but I can't see the harm in consistency so I'm happy with this
> > change. If my memory of the hardware is correct then the tiler power off
> > actually does very little and so I wouldn't expect it to take very long.
>
> I’ve seen tiler timeouts once I think and thus included it, but not since
> the values were increased. As long as it’s acceptable I won’t over-think
> it but if more testing is needed I can look at it more.

Thanks for clarifying.

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>