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drm/vc4: crtc: Reduce PV fifo threshold on hvs4 

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: c8b75bca92 ("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
This commit is contained in:
Dom Cobley 2021-03-18 17:13:28 +01:00 committed by Maxime Ripard
parent 35d65ab3fd
commit eb9dfdd1ed
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1 changed files with 17 additions and 0 deletions
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17
drivers/gpu/drm/vc4/vc4_crtc.c
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@ -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;
}
}