From: Paulo Zanoni Date: Fri, 7 Mar 2014 23:08:18 +0000 (-0300) Subject: drm/i915: update the PC8 and runtime PM documentation X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=765dab67528ac2490d8a9f68d05cc678861584d6;p=linux-beck.git drm/i915: update the PC8 and runtime PM documentation Now that PC8 got much simpler, there are less things to document. Also, runtime PM already has a nice documentation, so we don't need to re-explain it on our driver. v2: - Rebase. - Fix typo (Jesse). Reviewed-by: Jesse Barnes Signed-off-by: Paulo Zanoni Signed-off-by: Daniel Vetter --- diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 20db5d804e20..9cd870fb1472 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -1337,47 +1337,19 @@ struct ilk_wm_values { }; /* - * This struct tracks the state needed for the Package C8+ feature. + * This struct helps tracking the state needed for runtime PM, which puts the + * device in PCI D3 state. Notice that when this happens, nothing on the + * graphics device works, even register access, so we don't get interrupts nor + * anything else. * - * TODO: we're merging the Package C8+ feature with the runtime PM support. To - * avoid having to update the documentation at each patch of the series, we'll - * do a final update at the end. + * Every piece of our code that needs to actually touch the hardware needs to + * either call intel_runtime_pm_get or call intel_display_power_get with the + * appropriate power domain. * - * Package states C8 and deeper are really deep PC states that can only be - * reached when all the devices on the system allow it, so even if the graphics - * device allows PC8+, it doesn't mean the system will actually get to these - * states. - * - * Our driver only allows PC8+ when all the outputs are disabled, the power well - * is disabled and the GPU is idle. When these conditions are met, we manually - * do the other conditions: disable the interrupts, clocks and switch LCPLL - * refclk to Fclk. - * - * When we really reach PC8 or deeper states (not just when we allow it) we lose - * the state of some registers, so when we come back from PC8+ we need to - * restore this state. We don't get into PC8+ if we're not in RC6, so we don't - * need to take care of the registers kept by RC6. - * - * The interrupt disabling is part of the requirements. We can only leave the - * PCH HPD interrupts enabled. If we're in PC8+ and we get another interrupt we - * can lock the machine. - * - * Ideally every piece of our code that needs PC8+ disabled would call - * hsw_disable_package_c8, which would increment disable_count and prevent the - * system from reaching PC8+. But we don't have a symmetric way to do this for - * everything, so we have the requirements_met variable. When we switch - * requirements_met to true we decrease disable_count, and increase it in the - * opposite case. The requirements_met variable is true when all the CRTCs, - * encoders and the power well are disabled. - * - * In addition to everything, we only actually enable PC8+ if disable_count - * stays at zero for at least some seconds. This is implemented with the - * enable_work variable. We do this so we don't enable/disable PC8 dozens of - * consecutive times when all screens are disabled and some background app - * queries the state of our connectors, or we have some application constantly - * waking up to use the GPU. Only after the enable_work function actually - * enables PC8+ the "enable" variable will become true, which means that it can - * be false even if disable_count is 0. + * Our driver uses the autosuspend delay feature, which means we'll only really + * suspend if we stay with zero refcount for a certain amount of time. The + * default value is currently very conservative (see intel_init_runtime_pm), but + * it can be changed with the standard runtime PM files from sysfs. * * The irqs_disabled variable becomes true exactly after we disable the IRQs and * goes back to false exactly before we reenable the IRQs. We use this variable @@ -1387,7 +1359,7 @@ struct ilk_wm_values { * inside struct regsave so when we restore the IRQs they will contain the * latest expected values. * - * For more, read "Display Sequences for Package C8" on our documentation. + * For more, read the Documentation/power/runtime_pm.txt. */ struct i915_runtime_pm { bool suspended; diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c index 2fd53bc697aa..5f68491ae99a 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -7024,6 +7024,29 @@ static void hsw_restore_lcpll(struct drm_i915_private *dev_priv) spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags); } +/* + * Package states C8 and deeper are really deep PC states that can only be + * reached when all the devices on the system allow it, so even if the graphics + * device allows PC8+, it doesn't mean the system will actually get to these + * states. Our driver only allows PC8+ when going into runtime PM. + * + * The requirements for PC8+ are that all the outputs are disabled, the power + * well is disabled and most interrupts are disabled, and these are also + * requirements for runtime PM. When these conditions are met, we manually do + * the other conditions: disable the interrupts, clocks and switch LCPLL refclk + * to Fclk. If we're in PC8+ and we get an non-hotplug interrupt, we can hard + * hang the machine. + * + * When we really reach PC8 or deeper states (not just when we allow it) we lose + * the state of some registers, so when we come back from PC8+ we need to + * restore this state. We don't get into PC8+ if we're not in RC6, so we don't + * need to take care of the registers kept by RC6. Notice that this happens even + * if we don't put the device in PCI D3 state (which is what currently happens + * because of the runtime PM support). + * + * For more, read "Display Sequences for Package C8" on the hardware + * documentation. + */ void hsw_enable_pc8(struct drm_i915_private *dev_priv) { struct drm_device *dev = dev_priv->dev;