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>

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,

drivers/gpu/drm/i915/intel_dp.c

@@ -2711,8 +2711,12 @@ intel_dp_init(struct drm_device *dev, int output_reg, enum port port)
 			(final.t8 << PANEL_LIGHT_ON_DELAY_SHIFT);
 		pp_off = (final.t9 << PANEL_LIGHT_OFF_DELAY_SHIFT) |
 			 (final.t10 << PANEL_POWER_DOWN_DELAY_SHIFT);
-		pp_div = (pp_div & PP_REFERENCE_DIVIDER_MASK) |
-			 (DIV_ROUND_UP(final.t11_t12, 1000) << PANEL_POWER_CYCLE_DELAY_SHIFT);
+		/* Compute the divisor for the pp clock, simply match the Bspec
+		 * formula. */
+		pp_div = ((100 * intel_pch_rawclk(dev))/2 - 1)
+				<< PP_REFERENCE_DIVIDER_SHIFT;
+		pp_div |= (DIV_ROUND_UP(final.t11_t12, 1000)
+				<< PANEL_POWER_CYCLE_DELAY_SHIFT);
 
 		/* Haswell doesn't have any port selection bits for the panel
 		 * power sequence any more. */

drivers/gpu/drm/i915/intel_drv.h

@@ -405,6 +405,8 @@ struct intel_fbc_work {
 	int interval;
 };
 
+int intel_pch_rawclk(struct drm_device *dev);
+
 int intel_connector_update_modes(struct drm_connector *connector,
 				struct edid *edid);
 int intel_ddc_get_modes(struct drm_connector *c, struct i2c_adapter *adapter);