From 3ff60f89bc4836583f5bd195062f16c563bd97aa Mon Sep 17 00:00:00 2001 From: Oscar Mateo Date: Mon, 16 Jun 2014 16:10:58 +0100 Subject: [PATCH] drm/i915/vlv: Ack interrupts before handling them (VLV) Otherwise, we might receive a new interrupt before we have time to ack the first one, eventually missing it. Without an atomic XCHG operation with mmio space, this patch merely reduces the window in which we can miss an interrupt (especially when you consider how heavyweight the I915_READ/I915_WRITE operations are). Notice that, before clearing a port-sourced interrupt in the IIR, the corresponding interrupt source status in the PORT_HOTPLUG_STAT must be cleared. Spotted by Bob Beckett . v2: - Reorder the IIR clearing to reduce the window even further. - Add warning to commit message and comments to the code as per Chris Wilson's request. - Imre Deak pointed out that the pipe underrun flag might not be signaled in IIR, so do not make valleyview_pipestat_irq_handler depend on it. v3: Improve the source code comment. Signed-off-by: Oscar Mateo Reviewed-by: Imre Deak Signed-off-by: Daniel Vetter --- drivers/gpu/drm/i915/i915_irq.c | 67 +++++++++++++++++++-------------- 1 file changed, 38 insertions(+), 29 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c index 35c7e3a5b046..c434a6848c0f 100644 --- a/drivers/gpu/drm/i915/i915_irq.c +++ b/drivers/gpu/drm/i915/i915_irq.c @@ -1816,26 +1816,28 @@ static void i9xx_hpd_irq_handler(struct drm_device *dev) struct drm_i915_private *dev_priv = dev->dev_private; u32 hotplug_status = I915_READ(PORT_HOTPLUG_STAT); - if (IS_G4X(dev)) { - u32 hotplug_trigger = hotplug_status & HOTPLUG_INT_STATUS_G4X; + if (hotplug_status) { + I915_WRITE(PORT_HOTPLUG_STAT, hotplug_status); + /* + * Make sure hotplug status is cleared before we clear IIR, or else we + * may miss hotplug events. + */ + POSTING_READ(PORT_HOTPLUG_STAT); - intel_hpd_irq_handler(dev, hotplug_trigger, hpd_status_g4x); - } else { - u32 hotplug_trigger = hotplug_status & HOTPLUG_INT_STATUS_I915; + if (IS_G4X(dev)) { + u32 hotplug_trigger = hotplug_status & HOTPLUG_INT_STATUS_G4X; - intel_hpd_irq_handler(dev, hotplug_trigger, hpd_status_i915); - } + intel_hpd_irq_handler(dev, hotplug_trigger, hpd_status_g4x); + } else { + u32 hotplug_trigger = hotplug_status & HOTPLUG_INT_STATUS_I915; - if ((IS_G4X(dev) || IS_VALLEYVIEW(dev)) && - hotplug_status & DP_AUX_CHANNEL_MASK_INT_STATUS_G4X) - dp_aux_irq_handler(dev); + intel_hpd_irq_handler(dev, hotplug_trigger, hpd_status_i915); + } - I915_WRITE(PORT_HOTPLUG_STAT, hotplug_status); - /* - * Make sure hotplug status is cleared before we clear IIR, or else we - * may miss hotplug events. - */ - POSTING_READ(PORT_HOTPLUG_STAT); + if ((IS_G4X(dev) || IS_VALLEYVIEW(dev)) && + hotplug_status & DP_AUX_CHANNEL_MASK_INT_STATUS_G4X) + dp_aux_irq_handler(dev); + } } static irqreturn_t valleyview_irq_handler(int irq, void *arg) @@ -1846,29 +1848,36 @@ static irqreturn_t valleyview_irq_handler(int irq, void *arg) irqreturn_t ret = IRQ_NONE; while (true) { - iir = I915_READ(VLV_IIR); + /* Find, clear, then process each source of interrupt */ + gt_iir = I915_READ(GTIIR); + if (gt_iir) + I915_WRITE(GTIIR, gt_iir); + pm_iir = I915_READ(GEN6_PMIIR); + if (pm_iir) + I915_WRITE(GEN6_PMIIR, pm_iir); + + iir = I915_READ(VLV_IIR); + if (iir) { + /* Consume port before clearing IIR or we'll miss events */ + if (iir & I915_DISPLAY_PORT_INTERRUPT) + i9xx_hpd_irq_handler(dev); + I915_WRITE(VLV_IIR, iir); + } if (gt_iir == 0 && pm_iir == 0 && iir == 0) goto out; ret = IRQ_HANDLED; - snb_gt_irq_handler(dev, dev_priv, gt_iir); - - valleyview_pipestat_irq_handler(dev, iir); - - /* Consume port. Then clear IIR or we'll miss events */ - if (iir & I915_DISPLAY_PORT_INTERRUPT) - i9xx_hpd_irq_handler(dev); - + if (gt_iir) + snb_gt_irq_handler(dev, dev_priv, gt_iir); if (pm_iir) gen6_rps_irq_handler(dev_priv, pm_iir); - - I915_WRITE(GTIIR, gt_iir); - I915_WRITE(GEN6_PMIIR, pm_iir); - I915_WRITE(VLV_IIR, iir); + /* Call regardless, as some status bits might not be + * signalled in iir */ + valleyview_pipestat_irq_handler(dev, iir); } out: -- 2.34.1