[Intel-gfx] [PATCH] drm/i915: Avoid race of intel_crt_detect_hotplug() with HPD interrupt, v2
Egbert Eich
eich at suse.de
Wed Sep 23 07:15:27 PDT 2015
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 at suse.de>
---
drivers/gpu/drm/i915/i915_drv.h | 3 ++
drivers/gpu/drm/i915/i915_irq.c | 64 ++++++++++++++++++++++++++++++++--------
drivers/gpu/drm/i915/intel_crt.c | 11 ++++---
3 files changed, 59 insertions(+), 19 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index bf33d6e..a6b7576 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2737,6 +2737,9 @@ i915_disable_pipestat(struct drm_i915_private *dev_priv, enum pipe pipe,
void valleyview_enable_display_irqs(struct drm_i915_private *dev_priv);
void valleyview_disable_display_irqs(struct drm_i915_private *dev_priv);
+void i915_hotplug_interrupt_update(struct drm_i915_private *dev_priv,
+ uint32_t mask,
+ uint32_t bits);
void
ironlake_enable_display_irq(struct drm_i915_private *dev_priv, u32 mask);
void
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index a8aa797..ff85eae 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -167,6 +167,44 @@ static const u32 hpd_bxt[HPD_NUM_PINS] = {
static void gen6_rps_irq_handler(struct drm_i915_private *dev_priv, u32 pm_iir);
+/* For display hotplug interrupt */
+static inline void
+i915_hotplug_interrupt_update_locked(struct drm_i915_private *dev_priv,
+ uint32_t mask,
+ uint32_t bits)
+{
+ uint32_t val;
+
+ assert_spin_locked(&dev_priv->irq_lock);
+ WARN_ON(bits & ~mask);
+
+ val = I915_READ(PORT_HOTPLUG_EN);
+ val &= ~mask;
+ val |= bits;
+ I915_WRITE(PORT_HOTPLUG_EN, val);
+}
+
+/**
+ * i915_hotplug_interrupt_update - update hotplug interrupt enable
+ * @dev_priv: driver private
+ * @mask: bits to update
+ * @bits: bits to enable
+ * NOTE: the HPD enable bits are modified both inside and outside
+ * of an interrupt context. To avoid that read-modify-write cycles
+ * interfer, these bits are protected by a spinlock. Since this
+ * function is usually not called from a context where the lock is
+ * held already, this function acquires the lock itself. A non-locking
+ * version is also available.
+ */
+void i915_hotplug_interrupt_update(struct drm_i915_private *dev_priv,
+ uint32_t mask,
+ uint32_t bits)
+{
+ spin_lock_irq(&dev_priv->irq_lock);
+ i915_hotplug_interrupt_update_locked(dev_priv, mask, bits);
+ spin_unlock_irq(&dev_priv->irq_lock);
+}
+
/**
* ilk_update_display_irq - update DEIMR
* @dev_priv: driver private
@@ -3074,7 +3112,7 @@ static void vlv_display_irq_reset(struct drm_i915_private *dev_priv)
{
enum pipe pipe;
- I915_WRITE(PORT_HOTPLUG_EN, 0);
+ i915_hotplug_interrupt_update(dev_priv, 0xFFFFFFFF, 0);
I915_WRITE(PORT_HOTPLUG_STAT, I915_READ(PORT_HOTPLUG_STAT));
for_each_pipe(dev_priv, pipe)
@@ -3490,7 +3528,7 @@ static void vlv_display_irq_postinstall(struct drm_i915_private *dev_priv)
{
dev_priv->irq_mask = ~0;
- I915_WRITE(PORT_HOTPLUG_EN, 0);
+ i915_hotplug_interrupt_update(dev_priv, 0xffffffff, 0);
POSTING_READ(PORT_HOTPLUG_EN);
I915_WRITE(VLV_IIR, 0xffffffff);
@@ -3864,7 +3902,7 @@ static void i915_irq_preinstall(struct drm_device * dev)
int pipe;
if (I915_HAS_HOTPLUG(dev)) {
- I915_WRITE(PORT_HOTPLUG_EN, 0);
+ i915_hotplug_interrupt_update(dev_priv, 0xffffffff, 0);
I915_WRITE(PORT_HOTPLUG_STAT, I915_READ(PORT_HOTPLUG_STAT));
}
@@ -3898,7 +3936,7 @@ static int i915_irq_postinstall(struct drm_device *dev)
I915_USER_INTERRUPT;
if (I915_HAS_HOTPLUG(dev)) {
- I915_WRITE(PORT_HOTPLUG_EN, 0);
+ i915_hotplug_interrupt_update(dev_priv, 0xffffffff, 0);
POSTING_READ(PORT_HOTPLUG_EN);
/* Enable in IER... */
@@ -4060,7 +4098,7 @@ static void i915_irq_uninstall(struct drm_device * dev)
int pipe;
if (I915_HAS_HOTPLUG(dev)) {
- I915_WRITE(PORT_HOTPLUG_EN, 0);
+ i915_hotplug_interrupt_update(dev_priv, 0xffffffff, 0);
I915_WRITE(PORT_HOTPLUG_STAT, I915_READ(PORT_HOTPLUG_STAT));
}
@@ -4081,7 +4119,7 @@ static void i965_irq_preinstall(struct drm_device * dev)
struct drm_i915_private *dev_priv = dev->dev_private;
int pipe;
- I915_WRITE(PORT_HOTPLUG_EN, 0);
+ i915_hotplug_interrupt_update(dev_priv, 0xffffffff, 0);
I915_WRITE(PORT_HOTPLUG_STAT, I915_READ(PORT_HOTPLUG_STAT));
I915_WRITE(HWSTAM, 0xeffe);
@@ -4142,7 +4180,7 @@ static int i965_irq_postinstall(struct drm_device *dev)
I915_WRITE(IER, enable_mask);
POSTING_READ(IER);
- I915_WRITE(PORT_HOTPLUG_EN, 0);
+ i915_hotplug_interrupt_update(dev_priv, 0xffffffff, 0);
POSTING_READ(PORT_HOTPLUG_EN);
i915_enable_asle_pipestat(dev);
@@ -4157,22 +4195,22 @@ static void i915_hpd_irq_setup(struct drm_device *dev)
assert_spin_locked(&dev_priv->irq_lock);
- hotplug_en = I915_READ(PORT_HOTPLUG_EN);
- hotplug_en &= ~HOTPLUG_INT_EN_MASK;
/* Note HDMI and DP share hotplug bits */
/* enable bits are the same for all generations */
- hotplug_en |= intel_hpd_enabled_irqs(dev, hpd_mask_i915);
+ hotplug_en = intel_hpd_enabled_irqs(dev, hpd_mask_i915);
/* Programming the CRT detection parameters tends
to generate a spurious hotplug event about three
seconds later. So just do it once.
*/
if (IS_G4X(dev))
hotplug_en |= CRT_HOTPLUG_ACTIVATION_PERIOD_64;
- hotplug_en &= ~CRT_HOTPLUG_VOLTAGE_COMPARE_MASK;
hotplug_en |= CRT_HOTPLUG_VOLTAGE_COMPARE_50;
/* Ignore TV since it's buggy */
- I915_WRITE(PORT_HOTPLUG_EN, hotplug_en);
+ i915_hotplug_interrupt_update_locked(dev_priv,
+ (HOTPLUG_INT_EN_MASK
+ | CRT_HOTPLUG_VOLTAGE_COMPARE_MASK),
+ hotplug_en);
}
static irqreturn_t i965_irq_handler(int irq, void *arg)
@@ -4285,7 +4323,7 @@ static void i965_irq_uninstall(struct drm_device * dev)
if (!dev_priv)
return;
- I915_WRITE(PORT_HOTPLUG_EN, 0);
+ i915_hotplug_interrupt_update(dev_priv, 0xffffffff, 0);
I915_WRITE(PORT_HOTPLUG_STAT, I915_READ(PORT_HOTPLUG_STAT));
I915_WRITE(HWSTAM, 0xffffffff);
diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index af5e43b..6ce38e3 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -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;
}
--
1.8.4.5
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