Re: [PATCH 15/15] drm/i915: Simplify cursor register write sequence

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

On Sat, May 06, 2017 at 12:31:50AM +0300, Imre Deak wrote:
> On Mon, Mar 27, 2017 at 09:55:46PM +0300, ville.syrjala@linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > It looks like simply writing all the cursor register every single
> > time might be slightly faster than checking to see of each of
> > them need to be written. So if any other register apart from
> > CURPOS needs to be written let's just write all the registers.
> > 
> > CURPOS is left as a special case mainly for 845/865 where we have to
> > disable the cursor to change many of the cursor parameters. This
> > introduces a slight chance of the cursor flickering when things get
> > updated (since we're not currently doing the vblank evade for cursor
> > updates). If we write CURPOS alone then that obviously can't happen.
> > And let's follow the same pattern in the i9xx code just for symmetry.
> > I wasn't able to see a singificant performance difference between
> > this and just writing all the registers unconditionally.
> > 
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Reviewed-by: Imre Deak <imre.deak@intel.com>

Thanks for the reviews. Entire series pushed to dinq.

> 
> > ---
> >  drivers/gpu/drm/i915/intel_display.c | 69 ++++++++++++++++++------------------
> >  1 file changed, 34 insertions(+), 35 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index d78ab0d35274..40ac0f938a4e 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -9323,36 +9323,28 @@ static void i845_update_cursor(struct intel_plane *plane,
> >  
> >  	spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
> >  
> > -	if (plane->cursor.cntl != 0 &&
> > -	    (plane->cursor.base != base ||
> > -	     plane->cursor.size != size ||
> > -	     plane->cursor.cntl != cntl)) {
> > -		/* On these chipsets we can only modify the base/size/stride
> > -		 * whilst the cursor is disabled.
> > -		 */
> > +	/* On these chipsets we can only modify the base/size/stride
> > +	 * whilst the cursor is disabled.
> > +	 */
> > +	if (plane->cursor.base != base ||
> > +	    plane->cursor.size != size ||
> > +	    plane->cursor.cntl != cntl) {
> >  		I915_WRITE_FW(CURCNTR(PIPE_A), 0);
> > -		plane->cursor.cntl = 0;
> > -	}
> > -
> > -	if (plane->cursor.base != base)
> >  		I915_WRITE_FW(CURBASE(PIPE_A), base);
> > -
> > -	if (plane->cursor.size != size)
> >  		I915_WRITE_FW(CURSIZE, size);
> > -
> > -	if (cntl)
> >  		I915_WRITE_FW(CURPOS(PIPE_A), pos);
> > -
> > -	if (plane->cursor.cntl != cntl)
> >  		I915_WRITE_FW(CURCNTR(PIPE_A), cntl);
> >  
> > +		plane->cursor.base = base;
> > +		plane->cursor.size = size;
> > +		plane->cursor.cntl = cntl;
> > +	} else {
> > +		I915_WRITE_FW(CURPOS(PIPE_A), pos);
> > +	}
> > +
> >  	POSTING_READ_FW(CURCNTR(PIPE_A));
> >  
> >  	spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags);
> > -
> > -	plane->cursor.cntl = cntl;
> > -	plane->cursor.base = base;
> > -	plane->cursor.size = size;
> >  }
> >  
> >  static void i845_disable_cursor(struct intel_plane *plane,
> > @@ -9508,27 +9500,34 @@ static void i9xx_update_cursor(struct intel_plane *plane,
> >  
> >  	spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
> >  
> > -	if (plane->cursor.cntl != cntl)
> > +	/*
> > +	 * On some platforms writing CURCNTR first will also
> > +	 * cause CURPOS to be armed by the CURBASE write.
> > +	 * Without the CURCNTR write the CURPOS write would
> > +	 * arm itself.
> > +	 *
> > +	 * CURCNTR and CUR_FBC_CTL are always
> > +	 * armed by the CURBASE write only.
> > +	 */
> > +	if (plane->cursor.base != base ||
> > +	    plane->cursor.size != fbc_ctl ||
> > +	    plane->cursor.cntl != cntl) {
> >  		I915_WRITE_FW(CURCNTR(pipe), cntl);
> > -
> > -	if (plane->cursor.size != fbc_ctl)
> > -		I915_WRITE_FW(CUR_FBC_CTL(pipe), fbc_ctl);
> > -
> > -	if (cntl)
> > +		if (HAS_CUR_FBC(dev_priv))
> > +			I915_WRITE_FW(CUR_FBC_CTL(pipe), fbc_ctl);
> >  		I915_WRITE_FW(CURPOS(pipe), pos);
> > -
> > -	if (plane->cursor.cntl != cntl ||
> > -	    plane->cursor.size != fbc_ctl ||
> > -	    plane->cursor.base != base)
> >  		I915_WRITE_FW(CURBASE(pipe), base);
> >  
> > +		plane->cursor.base = base;
> > +		plane->cursor.size = fbc_ctl;
> > +		plane->cursor.cntl = cntl;
> > +	} else {
> > +		I915_WRITE_FW(CURPOS(pipe), pos);
> > +	}
> > +
> >  	POSTING_READ_FW(CURBASE(pipe));
> >  
> >  	spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags);
> > -
> > -	plane->cursor.cntl = cntl;
> > -	plane->cursor.base = base;
> > -	plane->cursor.size = fbc_ctl;
> >  }
> >  
> >  static void i9xx_disable_cursor(struct intel_plane *plane,
> > -- 
> > 2.10.2
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ville Syrjälä
Intel OTC
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