On Wed, 2013-02-06 at 11:10 +0000, Chris Wilson wrote:
> 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;
> +
Nitpick: this would be clearer in a seperate function with a
'check_only' param, then the below could be removed.
> /* 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. */
