Hi Dave, On Tue, Apr 05, 2022 at 01:00:28PM +0100, Dave Stevenson wrote: > On Tue, 5 Apr 2022 at 12:42, Laurent Pinchart wrote: > > On Sun, Feb 13, 2022 at 03:26:48AM +0100, Marek Vasut wrote: > > > In rare cases, the bridge may not start up correctly, which usually > > > leads to no display output. In case this happens, warn about it in > > > the kernel log. > > > > Do you know what this is caused by ? It's a bit annoying to add a 10+ms > > delay at start time just to be notified of rare cases. > > The datasheet [1] section 7.4.2 Initialization Sequence states in step 2 > "After power is applied and stable, the DSI CLK lanes MUST be in HS > state and the DSI data lanes MUST be driven > to LP11 state" > Data lanes shouldn't go to HS until step 8 after the DSI83 has been > configured. > > Configuration from the driver is being done from atomic_enable, > therefore the data lanes are likely in HS mode and sending video, not > LP11. > > Deviate from the specified initialisation sequence at your peril! > > The SN65DSI8[3|4|5] is one of the DSI devices that I'd been looking at > with the DSI ordering patches [2] so that we could initialise it in > the way specified in the datasheet. I've had no responses to v2 of > those patches though.
Sounds like I need to review that :-) It's still in my queue, I'll try to push it to the top. Do you think this patch could then be reverted ? > [1] https://www.ti.com/lit/ds/symlink/sn65dsi83.pdf > [2] https://patchwork.freedesktop.org/series/100252/#rev2 > > > > Signed-off-by: Marek Vasut <[email protected]> > > > Cc: Jagan Teki <[email protected]> > > > Cc: Laurent Pinchart <[email protected]> > > > Cc: Linus Walleij <[email protected]> > > > Cc: Robert Foss <[email protected]> > > > Cc: Sam Ravnborg <[email protected]> > > > Cc: [email protected] > > > --- > > > drivers/gpu/drm/bridge/ti-sn65dsi83.c | 5 +++++ > > > 1 file changed, 5 insertions(+) > > > > > > diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c > > > b/drivers/gpu/drm/bridge/ti-sn65dsi83.c > > > index 19daaddd29a41..1d7c154ea1d79 100644 > > > --- a/drivers/gpu/drm/bridge/ti-sn65dsi83.c > > > +++ b/drivers/gpu/drm/bridge/ti-sn65dsi83.c > > > @@ -488,6 +488,11 @@ static void sn65dsi83_atomic_enable(struct > > > drm_bridge *bridge, > > > /* Clear all errors that got asserted during initialization. */ > > > regmap_read(ctx->regmap, REG_IRQ_STAT, &pval); > > > regmap_write(ctx->regmap, REG_IRQ_STAT, pval); > > > + > > > + usleep_range(10000, 12000); > > > + regmap_read(ctx->regmap, REG_IRQ_STAT, &pval); > > > + if (pval) > > > + dev_err(ctx->dev, "Unexpected link status 0x%02x\n", pval); > > > } > > > > > > static void sn65dsi83_atomic_disable(struct drm_bridge *bridge, -- Regards, Laurent Pinchart
