Re: [Intel-gfx] [PATCH v3] drm/i915/display: Dual refresh rate fastset fixes with VRR fastset

[Jani Nikula <jani.nikula@linux.intel.com>]

On Mon, 14 Aug 2023, Manasi Navare <navaremanasi@chromium.org> wrote:
> Dual refresh rate (DRR) fastset seamlessly lets refresh rate
> throttle without needing a full modeset.

Is this something different from DRRS, or Dynamic Refresh Rate
Switching?

> However with the recent VRR fastset patches that got merged this
> logic was broken.

Which commits exactly? "recent patches" is a bit vague.

Is there a gitlab issue for this? Is it [1] or is that different?

[1] https://gitlab.freedesktop.org/drm/intel/-/issues/8851

> This is broken because now with VRR fastset
> VRR parameters are calculated by default at the nominal refresh rate say 120Hz.
> Now when DRR throttle happens to switch refresh rate to 60Hz, crtc clock
> changes and this throws a mismatch in VRR parameters and fastset logic
> for DRR gets thrown off and full modeset is indicated.
>
> This patch fixes this by ignoring the pipe mismatch for VRR parameters
> in the case of DRR and when VRR is not enabled. With this fix, DRR
> will still throttle seamlessly as long as VRR is not enabled.
>
> This will still need a full modeset for both DRR and VRR operating together
> during the refresh rate throttle and then enabling VRR since now VRR
> parameters need to be recomputed with new crtc clock and written to HW.
>
> This DRR + VRR fastset in conjunction needs more work in the driver and
> will be fixed in later patches.

I admit I have a hard time wrapping my head around the above explanation
with the code changes. :/

I'm hoping describing the "what broke" along with a regressing commit
would help it.

BR,
Jani.


>
> v3:
> Compute new VRR params whenever there is fastset and its non DRRS.
> This will ensure it computes while switching to a fixed RR (Mitul)
>
> v2:
> Check for pipe config mismatch in crtc clock whenever VRR is enabled
>
> Cc: Drew Davenport <ddavenport@chromium.org>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Sean Paul <seanpaul@chromium.org>
> Cc: Mitul Golani <mitulkumar.ajitkumar.golani@intel.com>
> Signed-off-by: Manasi Navare <navaremanasi@chromium.org>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index 763ab569d8f3..2cf3b22adaf7 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -5352,7 +5352,7 @@ intel_pipe_config_compare(const struct intel_crtc_state *current_config,
>  	if (IS_G4X(dev_priv) || DISPLAY_VER(dev_priv) >= 5)
>  		PIPE_CONF_CHECK_I(pipe_bpp);
>  
> -	if (!fastset || !pipe_config->seamless_m_n) {
> +	if (!fastset || !pipe_config->seamless_m_n || pipe_config->vrr.enable) {
>  		PIPE_CONF_CHECK_I(hw.pipe_mode.crtc_clock);
>  		PIPE_CONF_CHECK_I(hw.adjusted_mode.crtc_clock);
>  	}
> @@ -5387,11 +5387,13 @@ intel_pipe_config_compare(const struct intel_crtc_state *current_config,
>  
>  	if (!fastset)
>  		PIPE_CONF_CHECK_BOOL(vrr.enable);
> -	PIPE_CONF_CHECK_I(vrr.vmin);
> -	PIPE_CONF_CHECK_I(vrr.vmax);
> -	PIPE_CONF_CHECK_I(vrr.flipline);
> -	PIPE_CONF_CHECK_I(vrr.pipeline_full);
> -	PIPE_CONF_CHECK_I(vrr.guardband);
> +	if ((fastset && !pipe_config->seamless_m_n) || pipe_config->vrr.enable) {
> +		PIPE_CONF_CHECK_I(vrr.vmin);
> +		PIPE_CONF_CHECK_I(vrr.vmax);
> +		PIPE_CONF_CHECK_I(vrr.flipline);
> +		PIPE_CONF_CHECK_I(vrr.pipeline_full);
> +		PIPE_CONF_CHECK_I(vrr.guardband);
> +	}
>  
>  #undef PIPE_CONF_CHECK_X
>  #undef PIPE_CONF_CHECK_I

-- 
Jani Nikula, Intel Open Source Graphics Center