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

[Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>]

On Thu, Mar 16, 2023 at 11:06:08PM -0700, Dixit, Ashutosh wrote:
>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.

We could do that. I can move this to the open ioctl.

>>
>> 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?

Hmm, I was thinking of just keeping it in line with the other failures 
in open ioctl - a drm_err message, so that it helps debug.

>
>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.

Ideally patch 2 is required irrespective of the OA issue, since i915 
should make sure it honors the bios setting. With that in mind, I would 
leave the drm message in OA code.

>
>>
>> > +		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.
>>
will do

Thanks,
Umesh
>> > +	 */
>> > +	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