Re: [PATCH 1/9] drm/i915/wm: Reject SAGV consistently when block_time_us==0

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

On Tue, 2026-03-24 at 15:48 +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> We have three ways for the platform to indicate that
> SAGV is not supported:
> - pcode returns zero block time
> - pcode returns only a single QGV point (icl+)
> - pcode rejects the SAGV enable/disable command (pre-icl)
> 
> We don't currently consider all those factors when computing
> pipe_sagv_reject, meaning we might still try to enable
> SAGV when we should not.
> 
> I think one plausible scenario is when pcode returns a
> zero block time, and all the pipes are disabled. In
> that case intel_crtc_can_enable_sagv() will return true
> for all pipes, and thus we might try to enable SAGV
> despite pcode indicating that it's not supported.
> 
> Make sure pipe_sagv_reject will consistently reject
> SAGV when our cached block time is zero. That will cover
> all the aforementioned mechanisms by which SAGV can be
> disabled.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/skl_watermark.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 

Reviewed-by: Vinod Govindapillai <vinod.govindapillai@intel.com>

> diff --git a/drivers/gpu/drm/i915/display/skl_watermark.c
> b/drivers/gpu/drm/i915/display/skl_watermark.c
> index d45b3bcc6ef0..09988f46e083 100644
> --- a/drivers/gpu/drm/i915/display/skl_watermark.c
> +++ b/drivers/gpu/drm/i915/display/skl_watermark.c
> @@ -308,9 +308,6 @@ static bool skl_crtc_can_enable_sagv(const struct
> intel_crtc_state *crtc_state)
>  	enum plane_id plane_id;
>  	int max_level = INT_MAX;
>  
> -	if (!intel_has_sagv(display))
> -		return false;
> -
>  	if (!crtc_state->hw.active)
>  		return true;
>  
> @@ -377,6 +374,9 @@ bool intel_crtc_can_enable_sagv(const struct
> intel_crtc_state *crtc_state)
>  {
>  	struct intel_display *display =
> to_intel_display(crtc_state);
>  
> +	if (!display->sagv.block_time_us)
> +		return false;
> +
>  	if (!display->params.enable_sagv)
>  		return false;
>