Modifying the clock sources (via the DREF control on the PCH) is a slow
multi-stage process as we need to let the clocks stabilise between each
stage. If we are not actually changing the clock sources, then we can
return early.
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
drivers/gpu/drm/i915/intel_display.c | 83 +++++++++++++++++++++++++---------
1 file changed, 61 insertions(+), 22 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index d75c6a0..f1dbd01 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -4749,7 +4749,7 @@ static void ironlake_init_pch_refclk(struct drm_device *dev)
struct drm_i915_private *dev_priv = dev->dev_private;
struct drm_mode_config *mode_config = &dev->mode_config;
struct intel_encoder *encoder;
- u32 temp;
+ u32 val, final;
bool has_lvds = false;
bool has_cpu_edp = false;
bool has_pch_edp = false;
@@ -4792,70 +4792,109 @@ static void ironlake_init_pch_refclk(struct drm_device *dev)
* PCH B stepping, previous chipset stepping should be
* ignoring this setting.
*/
- temp = I915_READ(PCH_DREF_CONTROL);
+ val = I915_READ(PCH_DREF_CONTROL);
+
+ /* As we must carefully and slowly disable/enable each source in turn,
+ * compute the final state we want first and check if we need to
+ * make any changes at all.
+ */
+ final = val;
+ final &= ~DREF_NONSPREAD_SOURCE_MASK;
+ if (has_ck505)
+ final |= DREF_NONSPREAD_CK505_ENABLE;
+ else
+ final |= DREF_NONSPREAD_SOURCE_ENABLE;
+
+ final &= ~DREF_SSC_SOURCE_MASK;
+ final &= ~DREF_CPU_SOURCE_OUTPUT_MASK;
+ final &= ~DREF_SSC1_ENABLE;
+
+ if (has_panel) {
+ final |= DREF_SSC_SOURCE_ENABLE;
+
+ if (intel_panel_use_ssc(dev_priv) && can_ssc)
+ final |= DREF_SSC1_ENABLE;
+
+ if (has_cpu_edp) {
+ if (intel_panel_use_ssc(dev_priv) && can_ssc)
+ final |= DREF_CPU_SOURCE_OUTPUT_DOWNSPREAD;
+ else
+ final |= DREF_CPU_SOURCE_OUTPUT_NONSPREAD;
+ } else
+ final |= DREF_CPU_SOURCE_OUTPUT_DISABLE;
+ } else {
+ final |= DREF_SSC_SOURCE_DISABLE;
+ final |= DREF_CPU_SOURCE_OUTPUT_DISABLE;
+ }
+
+ if (final == val)
+ return;
+
/* Always enable nonspread source */
- temp &= ~DREF_NONSPREAD_SOURCE_MASK;
+ val &= ~DREF_NONSPREAD_SOURCE_MASK;
if (has_ck505)
- temp |= DREF_NONSPREAD_CK505_ENABLE;
+ val |= DREF_NONSPREAD_CK505_ENABLE;
else
- temp |= DREF_NONSPREAD_SOURCE_ENABLE;
+ val |= DREF_NONSPREAD_SOURCE_ENABLE;
if (has_panel) {
- temp &= ~DREF_SSC_SOURCE_MASK;
- temp |= DREF_SSC_SOURCE_ENABLE;
+ val &= ~DREF_SSC_SOURCE_MASK;
+ val |= DREF_SSC_SOURCE_ENABLE;
/* SSC must be turned on before enabling the CPU output */
if (intel_panel_use_ssc(dev_priv) && can_ssc) {
DRM_DEBUG_KMS("Using SSC on panel\n");
- temp |= DREF_SSC1_ENABLE;
+ val |= DREF_SSC1_ENABLE;
} else
- temp &= ~DREF_SSC1_ENABLE;
+ val &= ~DREF_SSC1_ENABLE;
/* Get SSC going before enabling the outputs */
- I915_WRITE(PCH_DREF_CONTROL, temp);
+ I915_WRITE(PCH_DREF_CONTROL, val);
POSTING_READ(PCH_DREF_CONTROL);
udelay(200);
- temp &= ~DREF_CPU_SOURCE_OUTPUT_MASK;
+ val &= ~DREF_CPU_SOURCE_OUTPUT_MASK;
/* Enable CPU source on CPU attached eDP */
if (has_cpu_edp) {
if (intel_panel_use_ssc(dev_priv) && can_ssc) {
DRM_DEBUG_KMS("Using SSC on eDP\n");
- temp |= DREF_CPU_SOURCE_OUTPUT_DOWNSPREAD;
+ val |= DREF_CPU_SOURCE_OUTPUT_DOWNSPREAD;
}
else
- temp |= DREF_CPU_SOURCE_OUTPUT_NONSPREAD;
+ val |= DREF_CPU_SOURCE_OUTPUT_NONSPREAD;
} else
- temp |= DREF_CPU_SOURCE_OUTPUT_DISABLE;
+ val |= DREF_CPU_SOURCE_OUTPUT_DISABLE;
- I915_WRITE(PCH_DREF_CONTROL, temp);
+ I915_WRITE(PCH_DREF_CONTROL, val);
POSTING_READ(PCH_DREF_CONTROL);
udelay(200);
} else {
DRM_DEBUG_KMS("Disabling SSC entirely\n");
- temp &= ~DREF_CPU_SOURCE_OUTPUT_MASK;
+ val &= ~DREF_CPU_SOURCE_OUTPUT_MASK;
/* Turn off CPU output */
- temp |= DREF_CPU_SOURCE_OUTPUT_DISABLE;
+ val |= DREF_CPU_SOURCE_OUTPUT_DISABLE;
- I915_WRITE(PCH_DREF_CONTROL, temp);
+ I915_WRITE(PCH_DREF_CONTROL, val);
POSTING_READ(PCH_DREF_CONTROL);
udelay(200);
/* Turn off the SSC source */
- temp &= ~DREF_SSC_SOURCE_MASK;
- temp |= DREF_SSC_SOURCE_DISABLE;
+ val &= ~DREF_SSC_SOURCE_MASK;
+ val |= DREF_SSC_SOURCE_DISABLE;
/* Turn off SSC1 */
- temp &= ~ DREF_SSC1_ENABLE;
+ val &= ~ DREF_SSC1_ENABLE;
- I915_WRITE(PCH_DREF_CONTROL, temp);
+ I915_WRITE(PCH_DREF_CONTROL, val);
POSTING_READ(PCH_DREF_CONTROL);
udelay(200);
}
+
+ BUG_ON(val != final);
}
/* Sequence to enable CLKOUT_DP for FDI usage and configure PCH FDI I/O. */
--
1.7.10.4
