[Intel-gfx] [PATCH 2/3] drm/i915: Evade transcoder's vblank when doing seamless M/N changes

[Golani, Mitulkumar Ajitkumar]

Hi Ville,

> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf Of Ville
> Syrjala
> Sent: 04 April 2023 23:25
> To: intel-gfx at lists.freedesktop.org
> Subject: [Intel-gfx] [PATCH 2/3] drm/i915: Evade transcoder's vblank when
> doing seamless M/N changes
> 
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> The transcoder M/N values are double buffered on the transcoder's
> undelayed vblank. So when doing seamless M/N fastsets we need to evade
> also that.
> 
> Not that currently the pipe's delayed vblank == transcoder's undelayed
> vblank, so this is still a nop change. But in the future when we may have to
> delay the pipe's vblank to create a register programming window
> ("window2") for the DSB.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_crtc.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_crtc.c
> b/drivers/gpu/drm/i915/display/intel_crtc.c
> index ed45a6934854..f3b836829296 100644
> --- a/drivers/gpu/drm/i915/display/intel_crtc.c
> +++ b/drivers/gpu/drm/i915/display/intel_crtc.c
> @@ -510,6 +510,13 @@ void intel_pipe_update_start(struct intel_crtc_state
> *new_crtc_state)
> 
> VBLANK_EVASION_TIME_US);
>  	max = vblank_start - 1;
> 
> +	/*
> +	 * M/N is double buffered on the transcoder's undelayed vblank,
> +	 * so with seamless M/N we must evade both vblanks.
> +	 */
> +	if (new_crtc_state->seamless_m_n &&
> intel_crtc_needs_fastset(new_crtc_state))
> +		min -= adjusted_mode->crtc_vblank_start -
> +adjusted_mode->crtc_vdisplay;
> +

changes LGTM. 
Thanks
 
Reviewed-by: Mitul Golani <mitulkumar.ajitkumar.golani at intel.com

>>  	if (min <= 0 || max <= 0)
>  		goto irq_disable;
> 
> --
> 2.39.2