Re: [PATCH 1/3] drm/i915: clarify PMINTRMSK/pm_intr_keep usage

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 12/09/2016 21:19, Dave Gordon wrote:
> No functional changes; just renaming a bit, tweaking a datatype,
> prettifying layout, and adding comments, in particular in the
> GuC setup code that touches this data.
>
> Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
> ---
>   drivers/gpu/drm/i915/i915_drv.h         |  1 +
>   drivers/gpu/drm/i915/i915_irq.c         |  4 ++--
>   drivers/gpu/drm/i915/i915_reg.h         |  2 +-
>   drivers/gpu/drm/i915/intel_guc_loader.c | 27 +++++++++++++++++++++------
>   4 files changed, 25 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 1e2dda8..d01a50e 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1184,6 +1184,7 @@ struct intel_gen6_power_mgmt {
>   	bool interrupts_enabled;
>   	u32 pm_iir;
>   
> +	/* PM interrupt bits that should never be masked */
>   	u32 pm_intr_keep;
>   
>   	/* Frequencies are stored in potentially platform dependent multiples.
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index 8462817..c128fdb 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -371,7 +371,7 @@ void gen6_disable_rps_interrupts(struct drm_i915_private *dev_priv)
>   	spin_lock_irq(&dev_priv->irq_lock);
>   	dev_priv->rps.interrupts_enabled = false;
>   
> -	I915_WRITE(GEN6_PMINTRMSK, gen6_sanitize_rps_pm_mask(dev_priv, ~0));
> +	I915_WRITE(GEN6_PMINTRMSK, gen6_sanitize_rps_pm_mask(dev_priv, ~0u));
>   
>   	__gen6_disable_pm_irq(dev_priv, dev_priv->pm_rps_events);
>   	I915_WRITE(gen6_pm_ier(dev_priv), I915_READ(gen6_pm_ier(dev_priv)) &
> @@ -4500,7 +4500,7 @@ void intel_irq_init(struct drm_i915_private *dev_priv)
>   		dev_priv->rps.pm_intr_keep |= GEN6_PM_RP_UP_EI_EXPIRED;
>   
>   	if (INTEL_INFO(dev_priv)->gen >= 8)
> -		dev_priv->rps.pm_intr_keep |= GEN8_PMINTR_REDIRECT_TO_NON_DISP;
> +		dev_priv->rps.pm_intr_keep |= GEN8_PMINTR_REDIRECT_TO_GUC;
>   
>   	INIT_DELAYED_WORK(&dev_priv->gpu_error.hangcheck_work,
>   			  i915_hangcheck_elapsed);
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index a29d707..70d9616 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -7067,7 +7067,7 @@ enum {
>   #define VLV_RCEDATA				_MMIO(0xA0BC)
>   #define GEN6_RC6pp_THRESHOLD			_MMIO(0xA0C0)
>   #define GEN6_PMINTRMSK				_MMIO(0xA168)
> -#define   GEN8_PMINTR_REDIRECT_TO_NON_DISP	(1<<31)
> +#define   GEN8_PMINTR_REDIRECT_TO_GUC		  (1<<31)
>   #define GEN8_MISC_CTRL0				_MMIO(0xA180)
>   #define VLV_PWRDWNUPCTL				_MMIO(0xA294)
>   #define GEN9_MEDIA_PG_IDLE_HYSTERESIS		_MMIO(0xA0C4)
> diff --git a/drivers/gpu/drm/i915/intel_guc_loader.c b/drivers/gpu/drm/i915/intel_guc_loader.c
> index 853928f..0021748 100644
> --- a/drivers/gpu/drm/i915/intel_guc_loader.c
> +++ b/drivers/gpu/drm/i915/intel_guc_loader.c
> @@ -134,13 +134,28 @@ static void direct_interrupts_to_guc(struct drm_i915_private *dev_priv)
>   	I915_WRITE(GUC_WD_VECS_IER, ~irqs);
>   
>   	/*
> -	 * If GuC has routed PM interrupts to itself, don't keep it.
> -	 * and keep other interrupts those are unmasked by GuC.
> -	*/
> +	 * The REDIRECT_TO_GUC bit of the PMINTRMSK register directs all
> +	 * (unmasked) PM interrupts to the GuC. All other bits of this
> +	 * register *disable* generation of a specific interrupt.
> +	 *
> +	 * 'pm_intr_keep' indicates bits that are NOT to be set when
> +	 * writing to the PM interrupt mask register, i.e. interrupts
> +	 * that must not be disabled.
> +	 *
> +	 * If the GuC is handling these interrupts, then we must not let
> +	 * the PM code disable ANY interrupt that the GuC is expecting.
> +	 * So for each ENABLED (0) bit in this register, we must SET the
> +	 * bit in pm_intr_keep so that it's left enabled for the GuC.
> +	 *
> +	 * OTOH the REDIRECT_TO_GUC bit is initially SET in pm_intr_keep
> +	 * (so interrupts go to the DISPLAY unit at first); but here we
> +	 * need to CLEAR that bit, which will result in the register bit
> +	 * being left SET!
> +	 */
>   	tmp = I915_READ(GEN6_PMINTRMSK);
> -	if (tmp & GEN8_PMINTR_REDIRECT_TO_NON_DISP) {
> -		dev_priv->rps.pm_intr_keep |= ~(tmp & ~GEN8_PMINTR_REDIRECT_TO_NON_DISP);
> -		dev_priv->rps.pm_intr_keep &= ~GEN8_PMINTR_REDIRECT_TO_NON_DISP;
> +	if (tmp & GEN8_PMINTR_REDIRECT_TO_GUC) {
> +		dev_priv->rps.pm_intr_keep |= ~tmp;
> +		dev_priv->rps.pm_intr_keep &= ~GEN8_PMINTR_REDIRECT_TO_GUC;
>   	}
>   }
>   

More comments is always good and the cleanup just above obviously good 
as well.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko

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