Re: [PATCH] drm/i915/guc: Skip suspend/resume GuC action on platforms w/o GuC submission

[Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>]

On 11/15/19 10:20 AM, don.hiatt@intel.com wrote:
> From: Don Hiatt <don.hiatt@intel.com>
> 
> On some platforms (e.g. KBL) that do not support GuC submission, but
> the user enabled the GuC communication (e.g for HuC authentication)
> calling the GuC EXIT_S_STATE action results in lose of ability to
> enter RC6. We can remove the GuC suspend/resume entirely as we do
> not need to save the GuC submission status.
> 
> Add intel_guc_submission_is_enabled() function to determine if
> GuC submission is active.
> 
> v2: Do not suspend/resume the GuC on platforms that do not support
>      Guc Submission.
> v3: Fix typo, move suspend logic to remove goto.
> v4: Use intel_guc_submission_is_enabled() to check GuC submission
>      status.
> v5: No need to look at engine to determine if submission is enabled.
>      Squash fix + intel_guc_submission_is_enabled() patch into one.
> 
> Reported-by: KiteStramuort <kitestramuort@autistici.org>
> Reported-by: S. Zharkoff <s.zharkoff@gmail.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111594
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111623
> Fixes: f774f0964919 ("drm/i915/guc: Turn on GuC/HuC auto mode")

I don't think this Fixes tag is appropriate since we already reverted 
that patch.

> Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
> Cc: Daniele Ceralo Spurio <daniele.ceraolospurio@intel.com>
> Cc: Stuart Summers <stuart.summers@intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Tested-by: Tomas Janousek <tomi@nomi.cz>
> Signed-off-by: Don Hiatt <don.hiatt@intel.com>
> ---
>   drivers/gpu/drm/i915/gt/uc/intel_guc.c | 7 +++++++
>   drivers/gpu/drm/i915/gt/uc/intel_uc.c  | 8 ++++++++
>   drivers/gpu/drm/i915/i915_drv.h        | 6 ++++++
>   3 files changed, 21 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.c b/drivers/gpu/drm/i915/gt/uc/intel_guc.c
> index 019ae6486e8d..92d9305c0d73 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.c
> @@ -553,6 +553,13 @@ int intel_guc_suspend(struct intel_guc *guc)
>   		GUC_POWER_D1, /* any value greater than GUC_POWER_D0 */
>   	};
>   
> +	/*
> +	 * If GuC communication is enabled but submission is not supported,
> +	 * we do not need to suspend the GuC.
> +	 */
> +	if (!intel_guc_submission_is_enabled(guc))
> +		return 0;
> +
>   	/*
>   	 * The ENTER_S_STATE action queues the save/restore operation in GuC FW
>   	 * and then returns, so waiting on the H2G is not enough to guarantee
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc.c b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> index 629b19377a29..4dd43b99a334 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> @@ -605,6 +605,14 @@ static int __uc_resume(struct intel_uc *uc, bool enable_communication)
>   	if (enable_communication)
>   		guc_enable_communication(guc);
>   
> +	/*
> +	 * If GuC communication is enabled but submission is not supported,
> +	 * we do not need to resume the GuC but we do need to enable the
> +	 * GuC communication on resume (above).
> +	 */
> +	if (!intel_guc_submission_is_enabled(guc))
> +		return 0;
> +

I would put this check inside intel_guc_resume(), for symmetry with the 
one you put inside intel_guc_suspend().

Daniele

>   	err = intel_guc_resume(guc);
>   	if (err) {
>   		DRM_DEBUG_DRIVER("Failed to resume GuC, err=%d", err);
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 7bc1d8c102b2..2b879472e760 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2044,4 +2044,10 @@ i915_coherent_map_type(struct drm_i915_private *i915)
>   	return HAS_LLC(i915) ? I915_MAP_WB : I915_MAP_WC;
>   }
>   
> +static inline bool intel_guc_submission_is_enabled(struct intel_guc *guc)
> +{
> +	return intel_guc_is_submission_supported(guc) &&
> +		intel_guc_is_running(guc);
> +}
> +
>   #endif
> 
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