Re: [PATCH] drm/omap: dsi: avoid sending bta sync all the time in writes
From: Andreas Kemnade
Date: Thu May 28 2026 - 13:04:20 EST
Hi,
so this droid4? Or which device is it?
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?
> [ 12.770385] omapdrm omapdrm.0: atomic complete timeout (pipe 0)!
> [ 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
looks like dsi is not involed here, so something else is producing problems?
> [ 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 out
> [ 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
>
>
Thanks for testing.
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>
> >
> >
>
>