[Intel-gfx] [PATCH] drm/i915: Perf_limit_reasons are only available for Gen11+

[Dixit, Ashutosh]

On Wed, 28 Sep 2022 04:38:46 -0700, Jani Nikula wrote:
>
> On Mon, 19 Sep 2022, Ashutosh Dixit <ashutosh.dixit at intel.com> wrote:
> > Register GT0_PERF_LIMIT_REASONS (0x1381a8) is available only for
> > Gen11+. Therefore ensure perf_limit_reasons sysfs/debugfs files are created
> > only for Gen11+. Otherwise on Gen < 5 accessing these files results in the
> > following oops:
> >
> > <1> [88.829420] BUG: unable to handle page fault for address: ffffc90000bb81a8
> > <1> [88.829438] #PF: supervisor read access in kernel mode
> > <1> [88.829447] #PF: error_code(0x0000) - not-present page
> >
> > Bspec: 20008
> > Bug: https://gitlab.freedesktop.org/drm/intel/-/issues/6863
> > Fixes: fe5979665f64 ("drm/i915/debugfs: Add perf_limit_reasons in debugfs")
> > Fixes: fa68bff7cf27 ("drm/i915/gt: Add sysfs throttle frequency interfaces")
> > Signed-off-by: Ashutosh Dixit <ashutosh.dixit at intel.com>
>

Hi Jani,

> Ashutosh, can you provide a backport of this i.e. commit 0d2d201095e9
> ("drm/i915: Perf_limit_reasons are only available for Gen11+") that
> applies cleanly on drm-intel-fixes, please?

I've sent the patch:

https://patchwork.freedesktop.org/series/109196/

Not sure though if it is worth applying on drm-intel-fixes because of one
conflict with drm-tip which will need to be resolved manually. On
drm-intel-fixes the crash mentioned above will be seen only on Gen < 5 if
someone manually cat's the sysfs. We had to fix on drm-tip because there
was a CI failure with Gen3 debugfs but that code is not in drm-intel-fixes.

Thanks.
--
Ashutosh