Re: [PATCH 3/5] drm/i915: Use old mbus_join value when increasing CDCLK

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Mar 22, 2024 at 01:40:44PM +0200, Stanislav Lisovskiy wrote:
> In order to make sure we are not breaking the proper sequence
> lets to updates step by step and don't change MBUS join value
> during MDCLK/CDCLK programming stage.
> MBUS join programming would be taken care by pre/post ddb hooks.
> 
> Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_cdclk.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
> index 31aaa9780dfcf..43a9616c78260 100644
> --- a/drivers/gpu/drm/i915/display/intel_cdclk.c
> +++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
> @@ -2611,9 +2611,19 @@ intel_set_cdclk_pre_plane_update(struct intel_atomic_state *state)
>  
>  	if (pipe == INVALID_PIPE ||
>  	    old_cdclk_state->actual.cdclk <= new_cdclk_state->actual.cdclk) {
> +		struct intel_cdclk_config cdclk_config;
> +
>  		drm_WARN_ON(&i915->drm, !new_cdclk_state->base.changed);
>  
> -		intel_set_cdclk(i915, &new_cdclk_state->actual, pipe);
> +		/*
> +		 * By this hack we want to prevent mbus_join to be programmed
> +		 * beforehand - we will take care of this later in pre ddb
> +		 * programming hook.
> +		 */

We're not doing anything to prevent mbus joining to be
programmed here. It will simply not be programmed here,
which is why we need to use the old mbus_join based ratio.

I would also include the actual function name here instead
of "pre ddb programming hook" since that's rather vague.

So this could use a bit of rewording. Otherwise lgtm
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> +		cdclk_config = new_cdclk_state->actual;
> +		cdclk_config.joined_mbus = old_cdclk_state->actual.joined_mbus;
> +
> +		intel_set_cdclk(i915, &cdclk_config, pipe);
>  	}
>  }
>  
> -- 
> 2.37.3

-- 
Ville Syrjälä
Intel