Re: [PATCH 02/12] drm/i915: Read PSR caps/intermediate freqs/etc. only once on eDP

Chris Wilson
2016-07-28T17:30:54Z

On Thu, Jul 28, 2016 at 05:50:38PM +0300, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Currently we re-read a bunch of static eDP panel caps from the DPCD
> over and over again. Let's do it only once to save some time and effort.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

> static bool
> intel_dp_get_dpcd(struct intel_dp *intel_dp)
> {
> - struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
> - struct drm_device *dev = dig_port->base.base.dev;
> - struct drm_i915_private *dev_priv = to_i915(dev);
> + bool init_edp_dpcd = is_edp(intel_dp) &&
> + intel_dp->dpcd[DP_DPCD_REV] == 0;
>
> if (drm_dp_dpcd_read(&intel_dp->aux, 0x000, intel_dp->dpcd,
> sizeof(intel_dp->dpcd)) < 0)

> + if (init_edp_dpcd)
> + intel_edp_get_dpcd(intel_dp);

I have to admit it took me a few passes to realise how this achieves
init once.

bool intel_dp_dpcd_is_unset(intel_dp)
{
return intel_dp->dpcd[DP_DPCD_REV] == 0;
}

Not really sure how else to make it clear to the causal reader that test
is only true on the first call.
-Chris

--
Chris Wilson, Intel Open Source Technology Centre