From: Daniel Kurtz <djkurtz@xxxxxxxxxxxx>
A framebuffer gets committed to FIMD's default window like this:
exynos_drm_crtc_update()
exynos_plane_commit()
fimd_win_commit()
fimd_win_commit() programs BUF_START[0]. At each vblank, FIMD hardware
copies the value from BUF_START to BUF_START_S (BUF_START's shadow
register), starts scanning out from BUF_START_S, and asserts its irq.
This irq is handled by fimd_irq_handler(), which calls
exynos_drm_crtc_finish_pageflip() to free the old buffer that FIMD just
finished scanning out, and potentially commit the next pending flip.
There is a race, however, if fimd_win_commit() programs BUF_START(0)
between the actual vblank irq, and its corresponding fimd_irq_handler().
=> FIMD vblank: BUF_START_S[0] := BUF_START[0], and irq asserted
| => fimd_win_commit(0) writes new BUF_START[0]
| exynos_drm_crtc_try_do_flip() marks exynos_fb as prepared
=> fimd_irq_handler()
exynos_drm_crtc_finish_pageflip() sees prepared exynos_fb,
and unmaps "old" fb
==> but, since BUF_START_S[0] still points to that "old" fb...
==> FIMD iommu fault
This patch ensures that fimd_irq_handler() only calls
exynos_drm_crtc_finish_pageflip() if any previously scheduled flip
has really completed.
This works because exynos_drm_crtc's flip fifo ensures that
fimd_win_commit() is never called more than once per
exynos_drm_crtc_finish_pageflip().
Signed-off-by: Daniel Kurtz <djkurtz@xxxxxxxxxxxx>
Reviewed-by: Sean Paul <seanpaul@xxxxxxxxxxxx>
Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/exynos/exynos_drm_fimd.c | 26 ++++++++++++++++++++++----
include/video/samsung_fimd.h | 1 +
2 files changed, 23 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/exynos/exynos_drm_fimd.c b/drivers/gpu/drm/exynos/exynos_drm_fimd.c
index e5810d1..b379182 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_fimd.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_fimd.c
@@ -55,6 +55,7 @@
#define VIDOSD_D(win) (VIDOSD_BASE + 0x0C + (win) * 16)
#define VIDWx_BUF_START(win, buf) (VIDW_BUF_START(buf) + (win) * 8)
+#define VIDWx_BUF_START_S(win, buf) (VIDW_BUF_START_S(buf) + (win) * 8)
#define VIDWx_BUF_END(win, buf) (VIDW_BUF_END(buf) + (win) * 8)
#define VIDWx_BUF_SIZE(win, buf) (VIDW_BUF_SIZE(buf) + (win) * 4)
@@ -1039,6 +1040,7 @@ static irqreturn_t fimd_irq_handler(int irq, void *dev_id)
{
struct fimd_context *ctx = (struct fimd_context *)dev_id;
u32 val, clear_bit;
+ u32 start, start_s;
val = readl(ctx->regs + VIDINTCON1);
@@ -1050,15 +1052,31 @@ static irqreturn_t fimd_irq_handler(int irq, void *dev_id)
if (ctx->pipe < 0 || !ctx->drm_dev)
goto out;
- if (ctx->i80_if) {
+ if (!ctx->i80_if)
+ drm_handle_vblank(ctx->drm_dev, ctx->pipe);
+
+ /*
+ * Ensure finish_pageflip is called iff a pending flip has completed.
+ * This works around a race between a page_flip request and the latency
+ * between vblank interrupt and this irq_handler:
+ * => FIMD vblank: BUF_START_S[0] := BUF_START[0], and asserts irq
+ * | => fimd_win_commit(0) writes new BUF_START[0]
+ * | exynos_drm_crtc_try_do_flip() marks exynos_fb as prepared
+ * => fimd_irq_handler()
+ * exynos_drm_crtc_finish_pageflip() sees prepared exynos_fb,
+ * and unmaps "old" fb
+ * ==> but, since BUF_START_S[0] still points to that "old" fb...
+ * ==> FIMD iommu fault
+ */
+ start = readl(ctx->regs + VIDWx_BUF_START(0, 0));
+ start_s = readl(ctx->regs + VIDWx_BUF_START_S(0, 0));
+ if (start == start_s)
exynos_drm_crtc_finish_pageflip(ctx->drm_dev, ctx->pipe);
+ if (ctx->i80_if) {
/* Exits triggering mode */
atomic_set(&ctx->triggering, 0);
} else {
- drm_handle_vblank(ctx->drm_dev, ctx->pipe);
- exynos_drm_crtc_finish_pageflip(ctx->drm_dev, ctx->pipe);
-
/* set wait vsync event to zero and wake up queue. */
if (atomic_read(&ctx->wait_vsync_event)) {
atomic_set(&ctx->wait_vsync_event, 0);
diff --git a/include/video/samsung_fimd.h b/include/video/samsung_fimd.h
index a20e4a3..f81d081 100644
--- a/include/video/samsung_fimd.h
+++ b/include/video/samsung_fimd.h
@@ -291,6 +291,7 @@
/* Video buffer addresses */
#define VIDW_BUF_START(_buff) (0xA0 + ((_buff) * 8))
+#define VIDW_BUF_START_S(_buff) (0x40A0 + ((_buff) * 8))
#define VIDW_BUF_START1(_buff) (0xA4 + ((_buff) * 8))
#define VIDW_BUF_END(_buff) (0xD0 + ((_buff) * 8))
#define VIDW_BUF_END1(_buff) (0xD4 + ((_buff) * 8))
--
1.9.3
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