drm/i915: add get_vblank_counter function for GM45

As discussed in the long thread about vblank related timeouts, it turns out
GM45 has different frame count registers than previous chips.  This patch
adds support for them, which prevents us from waiting on really stale
sequence values in drm_wait_vblank (which rather than returning immediately
ends up timing out or getting interrupted).

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Dave Airlie <airlied@linux.ie>

1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 6290219de6c8..548ff2c66431 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -174,6 +174,19 @@ u32 i915_get_vblank_counter(struct drm_device *dev, int pipe)
         return count;
 }
 
+u32 gm45_get_vblank_counter(struct drm_device *dev, int pipe)
+{
+        drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
+        int reg = pipe ? PIPEB_FRMCOUNT_GM45 : PIPEA_FRMCOUNT_GM45;
+
+        if (!i915_pipe_enabled(dev, pipe)) {
+                DRM_ERROR("trying to get vblank count for disabled pipe %d\n", pipe);
+                return 0;
+        }
+
+        return I915_READ(reg);
+}
+
 irqreturn_t i915_driver_irq_handler(DRM_IRQ_ARGS)
 {
         struct drm_device *dev = (struct drm_device *) arg;