[PATCH 5.11 185/210] drm/vc4: crtc: Reduce PV fifo threshold on hvs4

Greg Kroah-Hartman
2021-04-12T09:43:27Z

From: Dom Cobley <popcornmix@gmail.com>

[ Upstream commit eb9dfdd1ed40357b99a4201c8534c58c562e48c9 ]

Experimentally have found PV on hvs4 reports fifo full
error with expected settings and does not with one less

This appears as:
[drm:drm_atomic_helper_wait_for_flip_done] *ERROR* [CRTC:82:crtc-3] flip_done timed out

with bit 10 of PV_STAT set "HVS driving pixels when the PV FIFO is full"

Fixes: c8b75bca92cb ("drm/vc4: Add KMS support for Raspberry Pi.")
Signed-off-by: Dom Cobley <popcornmix@gmail.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20210318161328.1471556-3-maxime@cerno.tech
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/vc4/vc4_crtc.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)

diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
index ea710beb8e00..351c601f0ddb 100644
--- a/drivers/gpu/drm/vc4/vc4_crtc.c
+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
@@ -210,6 +210,7 @@ static u32 vc4_get_fifo_full_level(struct vc4_crtc *vc4_crtc, u32 format)
{
const struct vc4_crtc_data *crtc_data = vc4_crtc_to_vc4_crtc_data(vc4_crtc);
const struct vc4_pv_data *pv_data = vc4_crtc_to_vc4_pv_data(vc4_crtc);
+ struct vc4_dev *vc4 = to_vc4_dev(vc4_crtc->base.dev);
u32 fifo_len_bytes = pv_data->fifo_depth;

/*
@@ -238,6 +239,22 @@ static u32 vc4_get_fifo_full_level(struct vc4_crtc *vc4_crtc, u32 format)
if (crtc_data->hvs_output == 5)
return 32;

+ /*
+ * It looks like in some situations, we will overflow
+ * the PixelValve FIFO (with the bit 10 of PV stat being
+ * set) and stall the HVS / PV, eventually resulting in
+ * a page flip timeout.
+ *
+ * Displaying the video overlay during a playback with
+ * Kodi on an RPi3 seems to be a great solution with a
+ * failure rate around 50%.
+ *
+ * Removing 1 from the FIFO full level however
+ * seems to completely remove that issue.
+ */
+ if (!vc4->hvs->hvs5)
+ return fifo_len_bytes - 3 * HVS_FIFO_LATENCY_PIX - 1;
+
return fifo_len_bytes - 3 * HVS_FIFO_LATENCY_PIX;
}
}
--
2.30.2