Re: [PATCH 7/7] drm/i915: Stop RPS as we adjust thresholds

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> Disable RPS by setting RP_CONTROL to 0, remembering its earlier value.
> Then adjust the thresholds before re-enabling RP_CONTROL.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> Cc: stable@vger.kernel.org

Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>

> ---
>  drivers/gpu/drm/i915/intel_pm.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index d37e95b3525d..e5cfa0377367 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -4804,6 +4804,7 @@ static void gen6_set_rps_thresholds(struct drm_i915_private *dev_priv, u8 val)
>  	int new_power;
>  	u32 threshold_up = 0, threshold_down = 0; /* in % */
>  	u32 ei_up = 0, ei_down = 0;
> +	u32 rp_control;
>  
>  	new_power = dev_priv->rps.power;
>  	switch (dev_priv->rps.power) {
> @@ -4872,6 +4873,12 @@ static void gen6_set_rps_thresholds(struct drm_i915_private *dev_priv, u8 val)
>  	spin_lock_irq(&dev_priv->uncore.lock);
>  	intel_uncore_forcewake_get__locked(dev_priv, FORCEWAKE_ALL);
>  
> +	/* Stop RPS before changing thresholds */
> +	rp_control = I915_READ_FW(GEN6_RP_CONTROL);
> +	I915_WRITE_FW(GEN6_RP_CONTROL, 0);
> +	POSTING_READ_FW(GEN6_RP_CONTROL);
> +
> +	/* Update thresholds and evaluation intervals */
>  	I915_WRITE_FW(GEN6_RP_UP_EI,
>  		      GT_INTERVAL_FROM_US(dev_priv, ei_up));
>  	I915_WRITE_FW(GEN6_RP_UP_THRESHOLD,
> @@ -4885,8 +4892,7 @@ static void gen6_set_rps_thresholds(struct drm_i915_private *dev_priv, u8 val)
>  					  ei_down * threshold_down / 100));
>  
>  	/* Restart RPS to reload the thresholds */
> -	I915_WRITE_FW(GEN6_RP_CONTROL,
> -		      I915_READ_FW(GEN6_RP_CONTROL) | GEN6_RP_ENABLE);
> +	I915_WRITE_FW(GEN6_RP_CONTROL, rp_control | GEN6_RP_ENABLE);
>  
>  	intel_uncore_forcewake_put__locked(dev_priv, FORCEWAKE_ALL);
>  	spin_unlock_irq(&dev_priv->uncore.lock);
> -- 
> 2.11.0