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drm/i915: Fix comments about GMBUSFREQ register 

The comment about GMBUSFREQ is confused. The spec actually explains
the 4MHz thing perfectly by noting that the 4MHz divider values is
actually just bits [9:2] not [9:0], hence the divide by 1000 correct.
Replace the confused note with a quote from the spec, and eliminate
the duplicated comment that snuck in.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461689194-6079-4-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
This commit is contained in:
Ville Syrjälä 2016-04-26 19:46:34 +03:00
parent 1033f92e15
commit b5d99ff957
1 changed files with 5 additions and 10 deletions
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15
drivers/gpu/drm/i915/intel_display.c
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@ -5329,18 +5329,13 @@ static void intel_update_cdclk(struct drm_device *dev)
dev_priv->cdclk_freq); dev_priv->cdclk_freq);
/* /*
* Program the gmbus_freq based on the cdclk frequency. * 9:0 CMBUS [sic] CDCLK frequency (cdfreq):
* BSpec erroneously claims we should aim for 4MHz, but * Programmng [sic] note: bit[9:2] should be programmed to the number
* in fact 1MHz is the correct frequency. * of cdclk that generates 4MHz reference clock freq which is used to
* generate GMBus clock. This will vary with the cdclk freq.
*/ */
if (IS_VALLEYVIEW(dev) || IS_CHERRYVIEW(dev)) { if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))
/*
* Program the gmbus_freq based on the cdclk frequency.
* BSpec erroneously claims we should aim for 4MHz, but
* in fact 1MHz is the correct frequency.
*/
I915_WRITE(GMBUSFREQ_VLV, DIV_ROUND_UP(dev_priv->cdclk_freq, 1000)); I915_WRITE(GMBUSFREQ_VLV, DIV_ROUND_UP(dev_priv->cdclk_freq, 1000));
}
if (dev_priv->max_cdclk_freq == 0) if (dev_priv->max_cdclk_freq == 0)
intel_update_max_cdclk(dev); intel_update_max_cdclk(dev);