drm/i915: Use a spin lock to protect the pipe crc struct
Daniel pointed out that it was hard to get anything lockless to work
correctly, so don't even try for this non critical piece of code and
just use a spin lock.
v2: Make intel_pipe_crc->opened a bool
v3: Use assert_spin_locked() instead of a comment (Daniel Vetter)
v4: Use spin_lock_irq() in the debugfs functions (they can only be
called from process context),
Use spin_lock() in the pipe_crc_update() function that can only be
called from an interrupt handler,
Use wait_event_interruptible_lock_irq() when waiting for data in the
cicular buffer to ensure proper locking around the condition we are
waiting for. (Daniel Vetter)
Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 8f7baad..1a7dc77 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1200,15 +1200,19 @@
struct intel_pipe_crc_entry *entry;
int head, tail;
+ spin_lock(&pipe_crc->lock);
+
if (!pipe_crc->entries) {
+ spin_unlock(&pipe_crc->lock);
DRM_ERROR("spurious interrupt\n");
return;
}
- head = atomic_read(&pipe_crc->head);
- tail = atomic_read(&pipe_crc->tail);
+ head = pipe_crc->head;
+ tail = pipe_crc->tail;
if (CIRC_SPACE(head, tail, INTEL_PIPE_CRC_ENTRIES_NR) < 1) {
+ spin_unlock(&pipe_crc->lock);
DRM_ERROR("CRC buffer overflowing\n");
return;
}
@@ -1223,7 +1227,9 @@
entry->crc[4] = crc4;
head = (head + 1) & (INTEL_PIPE_CRC_ENTRIES_NR - 1);
- atomic_set(&pipe_crc->head, head);
+ pipe_crc->head = head;
+
+ spin_unlock(&pipe_crc->lock);
wake_up_interruptible(&pipe_crc->wq);
}