Re: [Intel-gfx] [PATCH 2/6] drm/i915: Rework SAGV block time probing

["Govindapillai, Vinod" <vinod.govindapillai@intel.com>]

On Tue, 2022-03-08 at 19:32 +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> I'd like to see the SAGV block time we got from the mailbox
> in the logs regardless of whether other factors prevent the
> use of SAGV.
> 
> So let's adjust the code to always query the SAGV block time,
> log it, and then reset it if SAGV is not actually supported.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Hi Ville,

I wonder if it is better to comprehend if we clean assigning  -1 to a u32 variable first before
this? I see that you are doing that anyway in the next patch in this series. Was there any
particular reason?

BR
Vinod

> ---
>  drivers/gpu/drm/i915/intel_pm.c | 38 +++++++++++++++++++--------------
>  1 file changed, 22 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 8ee31c9590a7..21c37115c36e 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3670,8 +3670,8 @@ intel_has_sagv(struct drm_i915_private *dev_priv)
>  		dev_priv->sagv_status != I915_SAGV_NOT_CONTROLLED;
>  }
>  
> -static void
> -skl_setup_sagv_block_time(struct drm_i915_private *dev_priv)
> +static u32
> +intel_sagv_block_time(struct drm_i915_private *dev_priv)
>  {
>  	if (DISPLAY_VER(dev_priv) >= 12) {
>  		u32 val = 0;
> @@ -3680,24 +3680,31 @@ skl_setup_sagv_block_time(struct drm_i915_private *dev_priv)
>  		ret = snb_pcode_read(dev_priv,
>  				     GEN12_PCODE_READ_SAGV_BLOCK_TIME_US,
>  				     &val, NULL);
> -		if (!ret) {
> -			dev_priv->sagv_block_time_us = val;
> -			return;
> +		if (ret) {
> +			drm_dbg_kms(&dev_priv->drm, "Couldn't read SAGV block time!\n");
> +			return -1;
>  		}
>  
> -		drm_dbg(&dev_priv->drm, "Couldn't read SAGV block time!\n");
> +		return val;
>  	} else if (DISPLAY_VER(dev_priv) == 11) {
> -		dev_priv->sagv_block_time_us = 10;
> -		return;
> -	} else if (DISPLAY_VER(dev_priv) == 9) {
> -		dev_priv->sagv_block_time_us = 30;
> -		return;
> +		return 10;
> +	} else if (DISPLAY_VER(dev_priv) == 9 && !IS_LP(dev_priv)) {
> +		return 30;
>  	} else {
> -		MISSING_CASE(DISPLAY_VER(dev_priv));
> +		/* Default to an unusable block time */
> +		return -1;
>  	}
> +}
>  
> -	/* Default to an unusable block time */
> -	dev_priv->sagv_block_time_us = -1;
> +static void intel_sagv_init(struct drm_i915_private *i915)
> +{
> +	i915->sagv_block_time_us = intel_sagv_block_time(i915);
> +
> +	drm_dbg_kms(&i915->drm, "SAGV supported: %s, original SAGV block time: %u us\n",
> +		    str_yes_no(intel_has_sagv(i915)), i915->sagv_block_time_us);
> +
> +	if (!intel_has_sagv(i915))
> +		i915->sagv_block_time_us = -1;
>  }
>  
>  /*
> @@ -8173,8 +8180,7 @@ void intel_init_pm(struct drm_i915_private *dev_priv)
>  	else if (GRAPHICS_VER(dev_priv) == 5)
>  		ilk_get_mem_freq(dev_priv);
>  
> -	if (intel_has_sagv(dev_priv))
> -		skl_setup_sagv_block_time(dev_priv);
> +	intel_sagv_init(dev_priv);
>  
>  	/* For FIFO watermark updates */
>  	if (DISPLAY_VER(dev_priv) >= 9) {