[PATCH 1/4] drm/i915/xe2lpd: Update bxt_sanitize_cdclk()

[Matt Roper]

On Thu, Jan 04, 2024 at 12:21:47AM -0300, Gustavo Sousa wrote:
> With Xe2_LPD, there were changes to the way CDCLK_CTL must be
> programmed. Those were reflected on _bxt_set_cdclk() with commit
> 3d3696c0fed1 ("drm/i915/lnl: Start using CDCLK through PLL"), but
> bxt_sanitize_cdclk() was left out.
> 
> This was causing some issues when loading the driver with a pre-existing
> active display configuration: the driver would mistakenly take the
> current value of CDCLK_CTL as wrong and the sanitization would be
> triggered.
> 
> In a scenario where the display was already configured with a high
> CDCLKC and had plane(s) enabled, FIFO underrun errors were reported,
> because the current sanitization code selects the minimum possible
> CDCLK.
> 
> Fix that by updating bxt_sanitize_cdclk() to match the changes made in
> _bxt_set_cdclk(). Ideally, we would have a common function to derive the
> value for CDCLK_CTL, but that can be done in a future change.
> 
> Signed-off-by: Gustavo Sousa <gustavo.sousa at intel.com>

Reviewed-by: Matt Roper <matthew.d.roper at intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_cdclk.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
> index c5fecde7afa8..0012e3171f3f 100644
> --- a/drivers/gpu/drm/i915/display/intel_cdclk.c
> +++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
> @@ -2071,7 +2071,10 @@ static void bxt_sanitize_cdclk(struct drm_i915_private *dev_priv)
>  	if (vco != dev_priv->display.cdclk.hw.vco)
>  		goto sanitize;
>  
> -	expected = skl_cdclk_decimal(cdclk);
> +	if (DISPLAY_VER(dev_priv) >= 20)
> +		expected = MDCLK_SOURCE_SEL_CDCLK_PLL;
> +	else
> +		expected = skl_cdclk_decimal(cdclk);
>  
>  	/* Figure out what CD2X divider we should be using for this cdclk */
>  	if (HAS_CDCLK_SQUASH(dev_priv))
> -- 
> 2.43.0
> 

-- 
Matt Roper
Graphics Software Engineer
Linux GPU Platform Enablement
Intel Corporation