Re: [PATCH v2] drm/i915: Increase WM memory latency values on SNB

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

On Thu, May 15, 2014 at 01:34:44PM +0300, Jani Nikula wrote:
> On Thu, 15 May 2014, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> > On Thu, May 15, 2014 at 01:13:21PM +0300, Jani Nikula wrote:
> >> On Thu, 08 May 2014, ville.syrjala@linux.intel.com wrote:
> >> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >> > +static void snb_wm_latency_quirk(struct drm_device *dev)
> >> > +{
> >> > +	struct drm_i915_private *dev_priv = dev->dev_private;
> >> > +	bool changed;
> >> > +
> >> > +	/*
> >> > +	 * The BIOS provided WM memory latency values are often
> >> > +	 * inadequate for high resolution displays. Adjust them.
> >> > +	 */
> >> > +	changed = ilk_increase_wm_latency(dev_priv, dev_priv->wm.pri_latency, 12) |
> >> > +		ilk_increase_wm_latency(dev_priv, dev_priv->wm.spr_latency, 12) |
> >> > +		ilk_increase_wm_latency(dev_priv, dev_priv->wm.cur_latency, 12);
> >> 
> >> Nitpick, s/|/||/g for bools.
> >
> > Consider side effects.
> 
> Ugh I'm slow today. Some might claim business as usual. I'll hide
> somewhere.
> 
> Before I head under the rock, may I say bitops on bools are still ugly?

I tend to use them but Paulo was also confused by them somewhere else
in the watermark code, so maybe I should stop using them?

I can rewrite as:
changed |= ilk_increase_wm_latency(dev_priv, dev_priv->wm.pri_latency, 12);
changed |= ilk_increase_wm_latency(dev_priv, dev_priv->wm.spr_latency, 12);
changed |= ilk_increase_wm_latency(dev_priv, dev_priv->wm.cur_latency, 12);

or just 3x
if (ilk_increase_wm_latency(...))
	changed = true;

if that helps.

-- 
Ville Syrjälä
Intel OTC