drm/imx: implement fence sync

If the FB is backed by a GEM object with an dma-buf attached
we need to wait for any pending fences to signal before executing
the page flip.

The implementation is straight forward by deferring the flip to
a workqueue in that case.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

diff --git a/drivers/gpu/drm/imx/ipuv3-crtc.c b/drivers/gpu/drm/imx/ipuv3-crtc.c
index a98b9b7..e6ae017 100644 (file)
--- a/drivers/gpu/drm/imx/ipuv3-crtc.c
+++ b/drivers/gpu/drm/imx/ipuv3-crtc.c
@@ -22,6 +22,8 @@
 #include <linux/fb.h>
 #include <linux/clk.h>
 #include <linux/errno.h>
+#include <linux/reservation.h>
+#include <linux/dma-buf.h>
 #include <drm/drm_gem_cma_helper.h>
 #include <drm/drm_fb_cma_helper.h>
 
@@ -34,12 +36,18 @@
 enum ipu_flip_status {
        IPU_FLIP_NONE,
        IPU_FLIP_PENDING,
+       IPU_FLIP_SUBMITTED,
 };
 
 struct ipu_flip_work {
        struct work_struct              unref_work;
        struct drm_gem_object           *bo;
        struct drm_pending_vblank_event *page_flip_event;
+       struct work_struct              fence_work;
+       struct ipu_crtc                 *crtc;
+       struct fence                    *excl;
+       unsigned                        shared_count;
+       struct fence                    **shared;
 };
 
 struct ipu_crtc {
@@ -123,11 +131,31 @@ static void ipu_flip_unref_work_func(struct work_struct *__work)
        kfree(work);
 }
 
+static void ipu_flip_fence_work_func(struct work_struct *__work)
+{
+       struct ipu_flip_work *work =
+                       container_of(__work, struct ipu_flip_work, fence_work);
+       int i;
+
+       /* wait for all fences attached to the FB obj to signal */
+       if (work->excl) {
+               fence_wait(work->excl, false);
+               fence_put(work->excl);
+       }
+       for (i = 0; i < work->shared_count; i++) {
+               fence_wait(work->shared[i], false);
+               fence_put(work->shared[i]);
+       }
+
+       work->crtc->flip_state = IPU_FLIP_SUBMITTED;
+}
+
 static int ipu_page_flip(struct drm_crtc *crtc,
                struct drm_framebuffer *fb,
                struct drm_pending_vblank_event *event,
                uint32_t page_flip_flags)
 {
+       struct drm_gem_cma_object *cma_obj = drm_fb_cma_get_gem_obj(fb, 0);
        struct ipu_crtc *ipu_crtc = to_ipu_crtc(crtc);
        struct ipu_flip_work *flip_work;
        int ret;
@@ -156,10 +184,41 @@ static int ipu_page_flip(struct drm_crtc *crtc,
        drm_gem_object_reference(flip_work->bo);
 
        ipu_crtc->flip_work = flip_work;
-       ipu_crtc->flip_state = IPU_FLIP_PENDING;
+       /*
+        * If the object has a DMABUF attached, we need to wait on its fences
+        * if there are any.
+        */
+       if (cma_obj->base.dma_buf) {
+               INIT_WORK(&flip_work->fence_work, ipu_flip_fence_work_func);
+               flip_work->crtc = ipu_crtc;
+
+               ret = reservation_object_get_fences_rcu(
+                               cma_obj->base.dma_buf->resv, &flip_work->excl,
+                               &flip_work->shared_count, &flip_work->shared);
+
+               if (unlikely(ret)) {
+                       DRM_ERROR("failed to get fences for buffer\n");
+                       goto free_flip_work;
+               }
+
+               /* No need to queue the worker if the are no fences */
+               if (!flip_work->excl && !flip_work->shared_count) {
+                       ipu_crtc->flip_state = IPU_FLIP_SUBMITTED;
+               } else {
+                       ipu_crtc->flip_state = IPU_FLIP_PENDING;
+                       queue_work(ipu_crtc->flip_queue,
+                                  &flip_work->fence_work);
+               }
+       } else {
+               ipu_crtc->flip_state = IPU_FLIP_SUBMITTED;
+       }
 
        return 0;
 
+free_flip_work:
+       drm_gem_object_unreference_unlocked(flip_work->bo);
+       kfree(flip_work);
+       ipu_crtc->flip_work = NULL;
 put_vblank:
        imx_drm_crtc_vblank_put(ipu_crtc->imx_crtc);
 
@@ -263,7 +322,7 @@ static irqreturn_t ipu_irq_handler(int irq, void *dev_id)
 
        imx_drm_handle_vblank(ipu_crtc->imx_crtc);
 
-       if (ipu_crtc->flip_state == IPU_FLIP_PENDING) {
+       if (ipu_crtc->flip_state == IPU_FLIP_SUBMITTED) {
                struct ipu_plane *plane = ipu_crtc->plane[0];
 
                ipu_plane_set_base(plane, ipu_crtc->base.primary->fb,