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drm/i915: Avoid race of intel_crt_detect_hotplug() with HPD interrupt, v2

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An HPD interrupt may fire while we are in a function that changes
the PORT_HOTPLUG_EN register - especially when an HPD interrupt
storm occurs.
Since the interrupt handler changes the enabled HPD lines when it
detects such a storm the read-modify-write cycles may interfere.
To avoid this, shiled the rmw cycles with IRQ save spinlocks.

Changes since v1:
- Implement a function which takes care of accessing PORT_HOTPLUG_EN.

Signed-off-by: Egbert Eich <eich@suse.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Egbert Eich
2015-09-23 16:15:27 +02:00
committed by Daniel Vetter
parent 8204502a6a
commit 0706f17c30
3 changed files with 59 additions and 19 deletions
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11
drivers/gpu/drm/i915/intel_crt.c
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@@ -376,7 +376,7 @@ static bool intel_crt_detect_hotplug(struct drm_connector *connector)
{
struct drm_device *dev = connector->dev;
struct drm_i915_private *dev_priv = dev->dev_private;
u32 hotplug_en, orig, stat;
u32 stat;
bool ret = false;
int i, tries = 0;
@@ -395,12 +395,12 @@ static bool intel_crt_detect_hotplug(struct drm_connector *connector)
tries = 2;
else
tries = 1;
hotplug_en = orig = I915_READ(PORT_HOTPLUG_EN);
hotplug_en |= CRT_HOTPLUG_FORCE_DETECT;
for (i = 0; i < tries ; i++) {
/* turn on the FORCE_DETECT */
I915_WRITE(PORT_HOTPLUG_EN, hotplug_en);
i915_hotplug_interrupt_update(dev_priv,
CRT_HOTPLUG_FORCE_DETECT,
CRT_HOTPLUG_FORCE_DETECT);
/* wait for FORCE_DETECT to go off */
if (wait_for((I915_READ(PORT_HOTPLUG_EN) &
CRT_HOTPLUG_FORCE_DETECT) == 0,
@@ -415,8 +415,7 @@ static bool intel_crt_detect_hotplug(struct drm_connector *connector)
/* clear the interrupt we just generated, if any */
I915_WRITE(PORT_HOTPLUG_STAT, CRT_HOTPLUG_INT_STATUS);
/* and put the bits back */
I915_WRITE(PORT_HOTPLUG_EN, orig);
i915_hotplug_interrupt_update(dev_priv, CRT_HOTPLUG_FORCE_DETECT, 0);
return ret;
}