Re: [Intel-gfx] [PATCH v7 11/11] drm/i915/perf: Wa_14017512683: Disable OAM if media C6 is enabled in BIOS

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

On Fri, 17 Mar 2023 16:16:41 -0700, Umesh Nerlige Ramappa wrote:
>

Hi Umesh,

Please read from bottom to top. Mostly nits but let's see what you think.

> 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.
>
> v2: (Ashutosh)
> - Remove drm_notice from the driver load path
> - Log a drm_err when opening an OAM stream on affected steppings
>
> Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_perf.c | 41 ++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
> index 18afa76653b7..823379d63caf 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"
>
> @@ -4216,6 +4217,20 @@ static int read_properties_unlocked(struct i915_perf *perf,
>		return -EINVAL;
>	}
>
> +	/*
> +	 * Wa_14017512683: mtl[a0..c0): Use of OAM must be preceded with Media
> +	 * C6 disable in BIOS. Fail if Media C6 is enabled on steppings where OAM
> +	 * does not work as expected.
> +	 */
> +	if (IS_MTL_MEDIA_STEP(props->engine->i915, STEP_A0, STEP_C0) &&
> +	    props->engine->gt->type == GT_MEDIA &&

Instead of gt type I think it's better to check perf_group->type. That is
why as I said below maybe better to have a valid perf_group even in this
case.

> +	    intel_check_bios_c6_setup(&props->engine->gt->rc6)) {
> +		drm_dbg(&perf->i915->drm,
> +			"OAM requires media C6 to be disabled in BIOS\n");
> +		return -EINVAL;
> +	}

So now we can change this check to something like:

	if (engine->perf_group->type == OAM && i915_perf->mtl_bios_mc6_enabled)

> +
> +
>	if (!engine_supports_oa(props->engine)) {
>		drm_dbg(&perf->i915->drm,
>			"Engine not supported by OA %d:%d\n",
> @@ -4897,6 +4912,15 @@ 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. To disable use of OAM with media engines, set the
> +	 * oa_group to PERF_GROUP_INVALID.
> +	 */
> +	if (IS_MTL_MEDIA_STEP(engine->i915, STEP_A0, STEP_C0) &&
> +	    intel_check_bios_c6_setup(&engine->gt->rc6))
> +		return PERF_GROUP_INVALID;

I think we should just remove this. Let the perf group be valid in this
case too since we cannot support OA for a different reason. Then we can use
the OAM perf group above.

Though if we drop this we have only 2 instances of the checks instead of 3
so maybe ok to not have i915_perf->mtl_bios_mc6_enabled?

> +
>	if (GRAPHICS_VER_FULL(engine->i915) >= IP_VER(12, 70)) {
>		/*
>		 * There's 1 SAMEDIA gt and 1 OAM per SAMEDIA gt. All media slices
> @@ -5316,6 +5340,23 @@ 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. If Media C6 is enabled in BIOS, return version 6
> +	 * to indicate that OA media is not supported.
> +	 */
> +	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))

Rather than repeat this comment and these checks (MTL stepping and
intel_check_bios_c6_setup) 3 times, I think it will be simpler to set a
variable (say i915_perf->mtl_bios_mc6_enabled) in i915_perf_init() and
reuse that in the 3 places.


> +				return 6;
> +		}
> +	}
> +
>	return 7;
>  }

Thanks.
--
Ashutosh