drm/i915: Use vblank evade mechanism in mmio_flip

Currently we program just DPSCNTR and DSPSTRIDE directly from the ring
interrupt handler, which is fine since the hardware guarantees that
those are update atomically. When we have atomic page flips we'll want
to be able to update also the offset registers, and then we need to use
the vblank evade mechanism to guarantee atomicity. Since that mechanism
introduces a wait, we need to do the actual register write from a work
when it is triggered by the ring interrupt.

v2: Explain the need for mmio_flip.work in the commit message (Paulo)
    Initialize the mmio_flip work in intel_crtc_init() (Paulo)
    Prevent new flips the previous flip work finishes (Paulo)
    Don't acquire modeset locks for mmio flip work

Note: Paulo had reservations about the work item leaking over a plane
disable. But insofar as we do lack these checks that issue is already
present with the existing code.

Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
index 0068fefd952e..64076555153a 100644
--- a/drivers/gpu/drm/i915/intel_sprite.c
+++ b/drivers/gpu/drm/i915/intel_sprite.c
@@ -76,7 +76,7 @@ static int usecs_to_scanlines(const struct drm_display_mode *mode, int usecs)
  *
  * Return: true if the call was successful
  */
-static bool intel_pipe_update_start(struct intel_crtc *crtc, uint32_t *start_vbl_count)
+bool intel_pipe_update_start(struct intel_crtc *crtc, uint32_t *start_vbl_count)
 {
 	struct drm_device *dev = crtc->base.dev;
 	const struct drm_display_mode *mode = &crtc->config.adjusted_mode;
@@ -149,7 +149,7 @@ static bool intel_pipe_update_start(struct intel_crtc *crtc, uint32_t *start_vbl
  * re-enables interrupts and verifies the update was actually completed
  * before a vblank using the value of @start_vbl_count.
  */
-static void intel_pipe_update_end(struct intel_crtc *crtc, u32 start_vbl_count)
+void intel_pipe_update_end(struct intel_crtc *crtc, u32 start_vbl_count)
 {
 	struct drm_device *dev = crtc->base.dev;
 	enum pipe pipe = crtc->pipe;