Re: [PATCH 6/9] drm/panthor: Reset GPU after L2 cache power off

Marek Vasut
2025-02-27T17:26:20Z

On 2/27/25 6:17 PM, Boris Brezillon wrote:

[...]

>> diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c b/drivers/gpu/drm/panthor/panthor_gpu.c
>> index 671049020afaa..0f07ef7d9aea7 100644
>> --- a/drivers/gpu/drm/panthor/panthor_gpu.c
>> +++ b/drivers/gpu/drm/panthor/panthor_gpu.c
>> @@ -470,11 +470,12 @@ int panthor_gpu_soft_reset(struct panthor_device *ptdev)
>> */
>> void panthor_gpu_suspend(struct panthor_device *ptdev)
>> {
>> - /* On a fast reset, simply power down the L2. */
>> - if (!ptdev->reset.fast)
>> - panthor_gpu_soft_reset(ptdev);
>> - else
>> - panthor_gpu_power_off(ptdev, L2, 1, 20000);
>> + /*
>> + * Power off the L2 and soft reset the GPU, that makes
>> + * iMX95 Mali G310 resume without firmware boot timeout.
>> + */
>> + panthor_gpu_power_off(ptdev, L2, 1, 20000);
>> + panthor_gpu_soft_reset(ptdev);
>
> Unfortunately, if you do that unconditionally we no longer have a
> fast-reset. Would be good to figure out why the fast-reset doesn't work
> on this platform.

I was hoping to get some hint on this one, I spent quite a while trying
to narrow this down, finally got it down to this particular bit.

The NXP downstream vendor kernel vendor Mali driver does not seem to
have anything interesting regarding the L2 power handling, but I might
have missed it, the code is difficult to read.

Have you ever seen anything problematic in this specific L2 department ?

Do you have any hints how I can debug this further ?