On Wed, 28 Sep 2011 10:09:13 +0100, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: > My understanding was that we could not enable SSC at all if we had a VGA, > DVI/HDMI or TV output; DP may or may not work with SSC. Yeah, which makes no sense at all. If this were true, we'd have to turn off the LVDS/eDP panel whenever enabling one of the non-SSC outputs. > The patch says that we will want to enable SSC if we have an SSC capbable > LVDS or eDP, which is certainly true. And that we can always do so if we > remember to set a magic bit in refclk to prevent non-SSC capable outputs > from being upset. I have not seen anything to support that last statement, > but, then again, I have not seen anything that actually explains what CK505 > is! CK505 is an Intel specification for external clock synthesizers. Here's an older one made by Silego: http://www.silego.com/uploads/Products/product_54/xSLG8SP585r101_10062009.pdf There are newer ones which provide the (required?) 120MHz output specified in the bspec. However, if you go read: http://www.advantech.com.tw/embcore/promotions/Whitepaper/2nd_Gen_Intel_Core_i7_Processors.pdf you'll see that Cougarpoint is reported to have a fully integrated clocking solution and not require an external CK505. Which makes the lack of the display_clock_mode bit in the VBIOS sources a lot more understandable. So, I think we should not look for a CK505 on Cougar Point systems, only on Ibex Peak systems, and that we probably cannot use SSC on Ibex Peak unless we have a CK505. > Having said that, this is an obvious improvement over the current > situation in that we do choose correctly in more circumstances and we do > not reprogram the refclk whilst active. I think we can reprogram the refclk after init time, but only if no-one is using it, which is something we can do later on. > As an incremental improvement [in my understanding ;-]: > Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Perhaps this patch on top of the existing patch? diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c index 1cc0962..4bf49eb 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -5122,6 +5122,8 @@ static void ironlake_init_pch_refclk(struct drm_device *dev) bool has_cpu_edp = false; bool has_pch_edp = false; bool has_panel = false; + bool has_ck505 = false; + bool can_ssc = false; /* We need to take the global config into account */ list_for_each_entry(encoder, &mode_config->encoder_list, @@ -5141,9 +5143,17 @@ static void ironlake_init_pch_refclk(struct drm_device *dev) } } + if (HAS_PCH_IBX(dev)) { + has_ck505 = dev_priv->display_clock_mode; + can_ssc = has_ck505; + } else { + has_ck505 = false; + can_ssc = true; + } + DRM_DEBUG_KMS("has_panel %d has_lvds %d has_pch_edp %d has_cpu_edp %d has_ck505 %d\n", has_panel, has_lvds, has_pch_edp, has_cpu_edp, - dev_priv->display_clock_mode); + has_ck505); /* Ironlake: try to setup display ref clock before DPLL * enabling. This is only under driver's control after @@ -5154,7 +5164,7 @@ static void ironlake_init_pch_refclk(struct drm_device *dev) /* Always enable nonspread source */ temp &= ~DREF_NONSPREAD_SOURCE_MASK; - if (dev_priv->display_clock_mode) + if (has_ck505) temp |= DREF_NONSPREAD_CK505_ENABLE; else temp |= DREF_NONSPREAD_SOURCE_ENABLE; @@ -5164,7 +5174,7 @@ static void ironlake_init_pch_refclk(struct drm_device *dev) temp |= DREF_SSC_SOURCE_ENABLE; /* SSC must be turned on before enabling the CPU output */ - if (intel_panel_use_ssc(dev_priv)) { + if (intel_panel_use_ssc(dev_priv) && can_ssc) { DRM_DEBUG_KMS("Using SSC on panel\n"); temp |= DREF_SSC1_ENABLE; } @@ -5178,7 +5188,7 @@ static void ironlake_init_pch_refclk(struct drm_device *dev) /* Enable CPU source on CPU attached eDP */ if (has_cpu_edp) { - if (intel_panel_use_ssc(dev_priv)) { + if (intel_panel_use_ssc(dev_priv) && can_ssc) { DRM_DEBUG_KMS("Using SSC on eDP\n"); temp |= DREF_CPU_SOURCE_OUTPUT_DOWNSPREAD; } -- keith.packard@xxxxxxxxx
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