gma500: Disable the clock gating of display controller to make DP/eDP work well

I don't know why the DP/eDP is affected by the clock gating. But the test
shows that it really fixes the DP/eDP clock issue during enabling DP/eDP.

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
[Updated to only apply the workaround if the device has DP. We don't want
 to do this on netbooks]
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/gma500/cdv_intel_dp.c

@@ -1778,6 +1778,28 @@ static bool cdv_intel_dpc_is_edp(struct drm_device *dev)
 	return false;
 }
 
+/* Cedarview display clock gating
+
+   We need this disable dot get correct behaviour while enabling
+   DP/eDP. TODO - investigate if we can turn it back to normality
+   after enabling */
+static void cdv_disable_intel_clock_gating(struct drm_device *dev)
+{
+	u32 reg_value;
+	reg_value = REG_READ(DSPCLK_GATE_D);
+
+	reg_value |= (DPUNIT_PIPEB_GATE_DISABLE |
+			DPUNIT_PIPEA_GATE_DISABLE |
+			DPCUNIT_CLOCK_GATE_DISABLE |
+			DPLSUNIT_CLOCK_GATE_DISABLE |
+			DPOUNIT_CLOCK_GATE_DISABLE |
+		 	DPIOUNIT_CLOCK_GATE_DISABLE);	
+
+	REG_WRITE(DSPCLK_GATE_D, reg_value);
+
+	udelay(500);		
+}
+
 void
 cdv_intel_dp_init(struct drm_device *dev, struct psb_intel_mode_device *mode_dev, int output_reg)
 {
@@ -1841,6 +1863,8 @@ cdv_intel_dp_init(struct drm_device *dev, struct psb_intel_mode_device *mode_dev
 			break;
 	}
 
+	cdv_disable_intel_clock_gating(dev);
+
 	cdv_intel_dp_i2c_init(psb_intel_connector, psb_intel_encoder, name);
         /* FIXME:fail check */
 	cdv_intel_dp_add_properties(connector);

drivers/gpu/drm/gma500/psb_intel_reg.h

@@ -1313,6 +1313,10 @@ No status bits are changed.
 # define VRHUNIT_CLOCK_GATE_DISABLE		(1 << 28) /* Fixed value on CDV */
 # define DPOUNIT_CLOCK_GATE_DISABLE		(1 << 11)
 # define DPIOUNIT_CLOCK_GATE_DISABLE		(1 << 6)
+# define DPUNIT_PIPEB_GATE_DISABLE		(1 << 30)
+# define DPUNIT_PIPEA_GATE_DISABLE		(1 << 25)
+# define DPCUNIT_CLOCK_GATE_DISABLE		(1 << 24)
+# define DPLSUNIT_CLOCK_GATE_DISABLE		(1 << 13)
 
 #define RAMCLK_GATE_D		0x6210