Re: [Intel-gfx] [PATCH v6 12/12] drm/i915/perf: Wa_14017512683: Disable OAM if media C6 is enabled in BIOS

["Dixit, Ashutosh" <ashutosh.dixit@intel.com>]

On Thu, 16 Mar 2023 22:14:52 -0700, Dixit, Ashutosh wrote:
>
> On Wed, 15 Mar 2023 18:01:01 -0700, Umesh Nerlige Ramappa wrote:
> >
>
> Hi Umesh,
>
> Mostly looks good but one nit below.
>
> > OAM does not work with media C6 enabled on some steppings of MTL.
> > Disable OAM if we detect that media C6 was enabled in bios.
> >
> > Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_perf.c | 30 ++++++++++++++++++++++++++++++
> >  1 file changed, 30 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
> > index 77fae3d80128..4ac6535a0356 100644
> > --- a/drivers/gpu/drm/i915/i915_perf.c
> > +++ b/drivers/gpu/drm/i915/i915_perf.c
> > @@ -209,6 +209,7 @@
> >  #include "gt/intel_gt_regs.h"
> >  #include "gt/intel_lrc.h"
> >  #include "gt/intel_lrc_reg.h"
> > +#include "gt/intel_rc6.h"
> >  #include "gt/intel_ring.h"
> >  #include "gt/uc/intel_guc_slpc.h"
> >
> > @@ -4898,6 +4899,18 @@ static u32 num_perf_groups_per_gt(struct intel_gt *gt)
> >
> >  static u32 __oam_engine_group(struct intel_engine_cs *engine)
> >  {
> > +	/*
> > +	 * Wa_14017512683: mtl[a0..c0): Use of OAM must be preceded with Media
> > +	 * C6 disable in BIOS. Do not enable OA for media classes if MC6 is
> > +	 * enabled in BIOS.
> > +	 */
> > +	if (IS_MTL_MEDIA_STEP(engine->i915, STEP_A0, STEP_C0) &&
> > +	    intel_check_bios_c6_setup(&engine->gt->rc6)) {
> > +		drm_notice_once(&engine->i915->drm,
> > +				"OAM requires media C6 to be disabled in BIOS\n");
>
> I think the typical mode of working with MTL would be to enable C6 unless OA
> is needed. But this will print out this notice on every MTL system. So IMO
> we should print this out only when a OAM perf stream is opened and that
> fails.
>
> Though not sure if it's ok to add a line to an already cluttered dmesg? The
> default console log level is 4 (WARNING) so maybe ok?
>
> https://linuxconfig.org/introduction-to-the-linux-kernel-log-levels
>
> Though if we fail the opening of an OAM stream we could make it a drm_warn?

Another idea: there is a drm_notice in Patch 2 when C6 is disabled, maybe
we could just change it to "C6 disabled by BIOS, OAM availbable\n" or
something like that and just remove the notice from here. I think we should
avoid the notice when C6 is enabled since that is likely to be the default
mode.

>
> > +		return PERF_GROUP_INVALID;
> > +	}
> > +
> >	if (GRAPHICS_VER_FULL(engine->i915) >= IP_VER(12, 70)) {
> >		/*
> >		 * There's 1 SAMEDIA gt and 1 OAM per SAMEDIA gt. All media slices
> > @@ -5317,6 +5330,23 @@ int i915_perf_ioctl_version(struct drm_i915_private *i915)
> >	 *
> >	 * 7: Add support for video decode and enhancement classes.
> >	 */
> > +
> > +	/*
> > +	 * Wa_14017512683: mtl[a0..c0): Use of OAM must be preceded with Media
> > +	 * C6 disable in BIOS. Do not enable OA for media classes if MC6 is
> > +	 * enabled in BIOS.
>
> Maybe add something like "Return version 6 to indicate non-support for OAM."
> just to make clear.
>
> > +	 */
> > +	if (IS_MTL_MEDIA_STEP(i915, STEP_A0, STEP_C0)) {
> > +		struct intel_gt *gt;
> > +		int i;
> > +
> > +		for_each_gt(gt, i915, i) {
> > +			if (gt->type == GT_MEDIA &&
> > +			    intel_check_bios_c6_setup(&gt->rc6))
> > +				return 6;
> > +		}
> > +	}
> > +
> >	return 7;
> >  }
> >
> > --
> > 2.36.1
> >
>
> Thanks.
> --
> Ashutosh