Re: [Intel-gfx] [PATCH v8 6/8] drm/i915: WA for platforms with double buffered adress update enable bit

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

On Mon, Sep 14, 2020 at 11:26:31AM +0530, Karthik B S wrote:
> In Gen 9 and Gen 10 platforms, async address update enable bit is
> double buffered. Due to this, during the transition from async flip
> to sync flip we have to wait until this bit is updated before continuing
> with the normal commit for sync flip.
> 
> Signed-off-by: Karthik B S <karthik.b.s@intel.com>
> Signed-off-by: Vandita Kulkarni <vandita.kulkarni@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c | 44 ++++++++++++++++++++
>  1 file changed, 44 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index a0c17d94daf3..b7e24dff0772 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -15360,6 +15360,42 @@ static void intel_enable_crtc(struct intel_atomic_state *state,
>  	intel_crtc_enable_pipe_crc(crtc);
>  }
>  
> +static void skl_toggle_async_sync(struct intel_atomic_state *state,

skl_disable_async_flip_wa() maybe?

> +				  struct intel_crtc *crtc,
> +				  struct intel_crtc_state *new_crtc_state)
> +{
> +	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
> +	struct intel_plane *plane;
> +	struct intel_plane_state *new_plane_state;
> +	u32 update_mask = new_crtc_state->update_planes;
> +	u32 plane_ctl, surf_addr;
> +	enum plane_id plane_id;
> +	unsigned long irqflags;
> +	enum pipe pipe;

Most of these things are only needed within the loop, so that's where
the declarations should be.

> +	int i;
> +
> +	for_each_new_intel_plane_in_state(state, plane, new_plane_state, i) {
> +		if (crtc->pipe != plane->pipe ||
> +		    !(update_mask & BIT(plane->id)))
> +			continue;
> +
> +		plane_id = plane->id;
> +		pipe = plane->pipe;
> +

I'd take the lock here so the rmw is fully protected.

> +		plane_ctl = intel_de_read_fw(dev_priv, PLANE_CTL(pipe, plane_id));
> +		surf_addr = intel_de_read_fw(dev_priv, PLANE_SURF(pipe, plane_id));
> +
> +		plane_ctl &= ~PLANE_CTL_ASYNC_FLIP;
> +
> +		spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
> +		intel_de_write_fw(dev_priv, PLANE_CTL(pipe, plane_id), plane_ctl);
> +		intel_de_write_fw(dev_priv, PLANE_SURF(pipe, plane_id), surf_addr);
> +		spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags);
> +	}
> +
> +	intel_wait_for_vblank(dev_priv, crtc->pipe);
> +}
> +
>  static void intel_update_crtc(struct intel_atomic_state *state,
>  			      struct intel_crtc *crtc)
>  {
> @@ -15387,6 +15423,14 @@ static void intel_update_crtc(struct intel_atomic_state *state,
>  	else
>  		intel_fbc_enable(state, crtc);
>  
> +	/* WA for older platforms where async address update enable bit

s/older//

> +	 * is double buffered.

"is double buffered and only latched at start of vblank" or
something. Otherwise one is left wondering what the fuss is about.

> +	 */

Multiline comment format should be
/*
 * blah
 * blah
 */

> +	if (old_crtc_state->uapi.async_flip &&
> +	    !new_crtc_state->uapi.async_flip &&
> +	    INTEL_GEN(dev_priv) <= 10 && INTEL_GEN(dev_priv) >= 9)

IS_GEN_RANGE(9, 10) or whatever it's called.

I guess we might want to put this call into intel_pre_plane_update()
since that's where all kinds of similar wait_for_vblank w/as live.

> +		skl_toggle_async_sync(state, crtc, new_crtc_state);
> +
>  	/* Perform vblank evasion around commit operation */
>  	intel_pipe_update_start(new_crtc_state);
>  
> -- 
> 2.22.0

-- 
Ville Syrjälä
Intel
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