Re: [PATCH] drm/omap: dsi: avoid sending bta sync all the time in writes

[Andreas Kemnade <akemnade@kernel.org>]

Hi,

so this droid4? Or which device is it?

On Thu, 28 May 2026 17:44:14 +0300
Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com> 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@kernel.org wrote:
> > From: Andreas Kemnade <andreas@kemnade.info>
> > 
> > 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@kemnade.info>
> > ---
> > 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@kernel.org>
> > 
> >   
> 
>