drm/i915/eDP: compute the panel power clock divisor from the pch rawclock

We need this when the bios forgets even to set that bit up. Most seem
to do that, even when they don't set up anything else in the panel
power sequencer.

Note that on IBX the rawclk is variable according to Bspec, but
everyone is using 125MHz. The rawclk is fixed to 125MHz on CPT, but
luckily we still have the same register available. On hsw, different
variants have different clocks, hence we need to check the register.

Since other pieces are driven by the rawclock, too, keep the little
helper in a central place.

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Tested-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 338570c8e0dc..0fb55429bb95 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -80,6 +80,16 @@ struct intel_limit {
 /* FDI */
 #define IRONLAKE_FDI_FREQ		2700000 /* in kHz for mode->clock */
 
+int
+intel_pch_rawclk(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	WARN_ON(!HAS_PCH_SPLIT(dev));
+
+	return I915_READ(PCH_RAWCLK_FREQ) & RAWCLK_FREQ_MASK;
+}
+
 static bool
 intel_find_best_PLL(const intel_limit_t *limit, struct drm_crtc *crtc,
 		    int target, int refclk, intel_clock_t *match_clock,