Re: [PATCH] drm/omap: dsi: avoid sending bta sync all the time in writes
From: Ivaylo Dimitrov
Date: Thu May 28 2026 - 13:48:57 EST
Hi,
On 28.05.26 г. 20:02 ч., Andreas Kemnade wrote:
Hi,
so this droid4? Or which device is it?
Oh, sorry, yes, this is droid4.
On Thu, 28 May 2026 17:44:14 +0300
Ivaylo Dimitrov <ivo.g.dimitrov.75@xxxxxxxxx> wrote:
Applied against 6.18.31, no dice :)
[ 11.617523] [drm] Initialized pvr 1.17.4948957 for 56000000.gpu on
minor 0
[ 11.674652] omapdss_dss 58000000.dss: bound 58001000.dispc (ops
dispc_component_ops [omapdrm])
[ 11.775085] omapdss_dss 58000000.dss: bound 58001000.dispc (ops
dsi_vc_flush_receive_data [omapdrm])
[ 12.222930] omapdss_dss 58000000.dss: bound 58001000.dispc (ops
dsi_vc_flush_receive_data [omapdrm])
[ 12.245117] omapdss_dss 58000000.dss: bound 58001000.dispc (ops
dsi_vc_flush_receive_data [omapdrm])
[ 12.247375] omapdss_dss 58000000.dss: bound 58004000.encoder (ops
dsi_vc_flush_receive_data [omapdrm])
[ 12.249267] omapdss_dss 58000000.dss: bound 58006000.encoder (ops
dsi_vc_flush_receive_data [omapdrm])
[ 12.284729] [drm] Initialized omapdrm 1.0.0 for omapdrm.0 on minor 1
[ 12.311981] [drm] Enabling DMM ywrap scrolling
I would expect some
output from the panel-dsi-cm driver:
dev_info(&ddata->dsi->dev, "panel revision %02x.%02x.%02x\n",
id1, id2, id3);
or some error:
dev_err(&ddata->dsi->dev, "error while enabling panel, issuing HW reset\n");
Any explanation why it is missing?
It is there, I grep-ed for omapdrm only, didn't want to flood the ML:
2026-05-28T17:34:45.761932+03:00 devuan-droid4 kernel: [ 12.502105] panel-dsi-cm 58004000.encoder.0: panel revision 70.01.02
Here is the (almost)full boot log: https://paste.debian.net/hidden/e6ca55a7
[ 12.770385] omapdrm omapdrm.0: atomic complete timeout (pipe 0)!looks like dsi is not involed here, so something else is producing problems?
[ 22.901306] omapdrm omapdrm.0: [drm] *ERROR* flip_done timed out
[ 22.901306] omapdrm omapdrm.0: [drm] *ERROR* [CRTC:67:crtc-0] commit
wait timed out
[ 33.131256] omapdrm omapdrm.0: [drm] *ERROR* flip_done timed out
[ 33.131378] omapdrm omapdrm.0: [drm] *ERROR* [CONNECTOR:66:DSI-1]
commit wait timed out
This might have something to do with the patch.
[ 43.371307] omapdrm omapdrm.0: [drm] *ERROR* flip_done timed outThanks for testing.
[ 43.371398] omapdrm omapdrm.0: [drm] *ERROR* [PLANE:34:plane-0]
commit wait timed out
[ 43.631408] omapdrm omapdrm.0: atomic complete timeout (pipe 0)!
[ 43.692504] omapdrm omapdrm.0: [drm] fb0: omapdrmdrmfb frame buffer
device
[ 54.251342] omapdrm omapdrm.0: [drm] *ERROR* flip_done timed out
[ 54.251464] omapdrm omapdrm.0: [drm] *ERROR* [CRTC:67:crtc-0] commit
wait timed out
[ 64.491302] omapdrm omapdrm.0: [drm] *ERROR* flip_done timed out
[ 64.491424] omapdrm omapdrm.0: [drm] *ERROR* [CONNECTOR:66:DSI-1]
commit wait timed out
[ 74.731323] omapdrm omapdrm.0: [drm] *ERROR* flip_done timed out
[ 74.731445] omapdrm omapdrm.0: [drm] *ERROR* [PLANE:34:plane-0]
commit wait timed out
[ 74.991363] omapdrm omapdrm.0: atomic complete timeout (pipe 0)!
[ 85.621307] omapdrm omapdrm.0: [drm] *ERROR* flip_done timed out
[ 85.621398] omapdrm omapdrm.0: [drm] *ERROR* [CRTC:67:crtc-0] commit
wait timed out
[ 95.851287] omapdrm omapdrm.0: [drm] *ERROR* flip_done timed out
[ 95.851379] omapdrm omapdrm.0: [drm] *ERROR* [CONNECTOR:66:DSI-1]
commit wait timed out
[ 106.101257] omapdrm omapdrm.0: [drm] *ERROR* flip_done timed out
[ 106.101440] omapdrm omapdrm.0: [drm] *ERROR* [PLANE:34:plane-0]
commit wait timed out
[ 106.371459] omapdrm omapdrm.0: atomic complete timeout (pipe 0)!
[ 106.961334] omapdrm omapdrm.0: atomic complete timeout (pipe 0)!
[ 141.301269] omapdrm omapdrm.0: [drm] *ERROR* flip_done timed out
[ 141.301269] omapdrm omapdrm.0: [drm] *ERROR* [CRTC:67:crtc-0] commit
wait timed out
[ 151.531280] omapdrm omapdrm.0: [drm] *ERROR* flip_done timed out
[ 151.531402] omapdrm omapdrm.0: [drm] *ERROR* [CONNECTOR:66:DSI-1]
commit wait timed out
You're welcome, I can do more testing as needed, ATM I am trying to upgrade leste to 6.18 anyways so have all tools in place. Feel free to ping me on leste IRC channel if you think I can be of any help here.
Regards,
Ivo
Regards,
Andreas
On 28.05.26 г. 13:16 ч., akemnade@xxxxxxxxxx wrote:
From: Andreas Kemnade <andreas@xxxxxxxxxxxx>
Some chips need configuration commands to be sent first, before they can
send data. TC358762 for example needs PPI_LPTXTIMECNT configured
and PPI_STARTPPI set to 1 to be able to transmit anything. To be able to
configure such chips, do not send bta sync during writes if no acks are
requested. Instead just wait for the packet to be sent to avoid FIFO
overflows. There might be more to do about acks, but there seem to be
virtually no users of that flag.
This came to light when fiddling with the Epson Moverio BT-200 display
which consists of 2 TC358762 bridges with SPI funneled through
to the unknown display chip. With that patch the bridge can be accessed,
Reading back registers works, when the above-mentioned registers are set.
Video mode panel at OMAP4 (BT-200) and video mode at OMAP5 was tested.
Fixes: e70965386353e ("drm/omap: dsi: simplify write function")
Signed-off-by: Andreas Kemnade <andreas@xxxxxxxxxxxx>
---
This was not tested on any command mode display, which IMHO should be
done. So droid4 folks: please give it a try
---
drivers/gpu/drm/omapdrm/dss/dsi.c | 32 +++++++++++++++++++++++---------
1 file changed, 23 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/omapdrm/dss/dsi.c b/drivers/gpu/drm/omapdrm/dss/dsi.c
index 27fe7bca9e2cf..98362b0157023 100644
--- a/drivers/gpu/drm/omapdrm/dss/dsi.c
+++ b/drivers/gpu/drm/omapdrm/dss/dsi.c
@@ -2194,6 +2194,7 @@ static int dsi_vc_send_null(struct dsi_data *dsi, int vc, int channel)
static int dsi_vc_write_common(struct omap_dss_device *dssdev, int vc,
const struct mipi_dsi_msg *msg)
{
+ DECLARE_COMPLETION_ONSTACK(completion);
struct dsi_data *dsi = to_dsi_data(dssdev);
int r;
@@ -2205,17 +2206,30 @@ static int dsi_vc_write_common(struct omap_dss_device *dssdev, int vc,
if (r < 0)
return r;
- /*
- * TODO: we do not always have to do the BTA sync, for example
- * we can improve performance by setting the update window
- * information without sending BTA sync between the commands.
- * In that case we can return early.
- */
+ /* wait for IRQ for long packet transmission confirmation */
+ r = dsi_register_isr_vc(dsi, vc, dsi_completion_handler,
+ &completion, DSI_VC_IRQ_PACKET_SENT);
+ if (r)
+ return r;
- r = dsi_vc_send_bta_sync(dssdev, vc);
- if (r) {
- DSSERR("bta sync failed\n");
+ if (wait_for_completion_timeout(&completion,
+ msecs_to_jiffies(500)) == 0)
+ r = -EIO;
+
+ dsi_unregister_isr_vc(dsi, vc, dsi_completion_handler,
+ &completion, DSI_VC_IRQ_PACKET_SENT);
+
+ if (r)
return r;
+
+ /* TODO: find out if more needs to be done for MIPI_DIS_MSG_REQ_ACK */
+
+ if (msg->flags & MIPI_DSI_MSG_REQ_ACK) {
+ r = dsi_vc_send_bta_sync(dssdev, vc);
+ if (r) {
+ DSSERR("bta sync failed\n");
+ return r;
+ }
}
/* RX_FIFO_NOT_EMPTY */
---
base-commit: e7ae89a0c97ce2b68b0983cd01eda67cf373517d
change-id: 20260528-vm-upstr-c8e7634ebf56
Best regards,
--
Andreas Kemnade <akemnade@xxxxxxxxxx>