<div dir="auto"><div><br><br><div class="gmail_quote"><div dir="ltr">On Sun, Aug 26, 2018, 1:44 AM <<a href="mailto:spanda@codeaurora.org" target="_blank" rel="noreferrer">spanda@codeaurora.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">On 2018-08-23 19:55, Sean Paul wrote:<br>
> On Tue, Aug 14, 2018 at 10:01:45AM -0400, Sean Paul wrote:<br>
>> On Tue, Aug 14, 2018 at 10:00:33AM -0400, Sean Paul wrote:<br>
>> > On Tue, Aug 14, 2018 at 04:59:31PM +0530, <a href="mailto:spanda@codeaurora.org" rel="noreferrer noreferrer" target="_blank">spanda@codeaurora.org</a> wrote:<br>
>> > > On 2018-08-14 03:00, Sean Paul wrote:<br>
>> > > > From: Sean Paul <<a href="mailto:seanpaul@chromium.org" rel="noreferrer noreferrer" target="_blank">seanpaul@chromium.org</a>><br>
>> > > ><br>
>> > > > This patch adds a 70ms mystery delay to the bridge driver in enable.<br>
>> > > > By experimentation, it seems like it can go anywhere up until we<br>
>> > > > initiate semi-auto link training. If we don't have the delay, link<br>
>> > > > training fails.<br>
>> > > ><br>
>> > > > I tried to root cause this as best I could, but neither the datasheet<br>
>> > > > for the panel nor the bridge mention a delay of this magnitude in their<br>
>> > > > timing requirements. So for now, add the mystery delay until someone<br>
>> > > > figures out a better fix.<br>
>> > > ><br>
>> > > > Changes in v3:<br>
>> > > > - Added to the set<br>
>> > > ><br>
>> > > > Cc: Sandeep Panda <<a href="mailto:spanda@codeaurora.org" rel="noreferrer noreferrer" target="_blank">spanda@codeaurora.org</a>><br>
>> > > > Signed-off-by: Sean Paul <<a href="mailto:seanpaul@chromium.org" rel="noreferrer noreferrer" target="_blank">seanpaul@chromium.org</a>><br>
>> > > > ---<br>
>> > > > drivers/gpu/drm/bridge/ti-sn65dsi86.c | 12 ++++++++++++<br>
>> > > > 1 file changed, 12 insertions(+)<br>
>> > > ><br>
>> > > > diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c<br>
>> > > > b/drivers/gpu/drm/bridge/ti-sn65dsi86.c<br>
>> > > > index d3e27e52ea759..f8a931cf3665e 100644<br>
>> > > > --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c<br>
>> > > > +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c<br>
>> > > > @@ -458,6 +458,18 @@ static void ti_sn_bridge_enable(struct drm_bridge<br>
>> > > > *bridge)<br>
>> > > > unsigned int val;<br>
>> > > > int ret;<br>
>> > > ><br>
>> > > > + /*<br>
>> > > > + * FIXME:<br>
>> > > > + * This 70ms was found necessary by experimentation. If it's not<br>
>> > > > + * present, link training fails. It seems like it can go anywhere from<br>
>> > > > + * pre_enable() up to semi-auto link training initiation below.<br>
>> > > > + *<br>
>> > > > + * Neither the datasheet for the bridge nor the panel tested mention a<br>
>> > > > + * delay of this magnitude in the timing requirements. So for now, add<br>
>> > > > + * the mystery delay until someone figures out a better fix.<br>
>> > > > + */<br>
>> > ><br>
>> > > Is this newly found issue? Specific to any board config?<br>
>> ><br>
>> > It's specific to cheza.<br>
>> <br>
>> Well, I suppose I shouldn't say that since I've not tried the bridge <br>
>> on another<br>
>> board. I should say, it reproduces on cheza.<br>
> <br>
> Ping. Sandeep: any more feedback?<br>
> <br>
> Sean<br>
> <br>
>> <br>
>> Sean<br>
>> <br>
>> > This was found with swboyd changed the panel regulator<br>
>> > from always-on/boot-on to toggle.<br>
>> ><br>
>> > I've pushed the tag "mtp-testing-0813" to dpu-staging so you can play around<br>
>> > with it. Without this delay, link training fails.<br>
>> ><br>
>> > Sean<br>
>> ><br>
>> > ><br>
>> > > > + msleep(70);<br>
>> > > > +<br>
>> > > > /* DSI_A lane config */<br>
>> > > > val = CHA_DSI_LANES(4 - pdata->dsi->lanes);<br>
>> > > > regmap_update_bits(pdata->regmap, SN_DSI_LANES_REG,<br>
>> ><br>
>> > --<br>
>> > Sean Paul, Software Engineer, Google / Chromium OS<br>
>> <br>
>> --<br>
>> Sean Paul, Software Engineer, Google / Chromium OS<br>
<br>
No more comments from my side.<br></blockquote></div></div><div dir="auto"><br></div><div dir="auto">So, should I find another reviewer? </div><div dir="auto"><br></div><div dir="auto">Sean</div><div dir="auto"><br></div><div dir="auto"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
Sandeep<br>
</blockquote></div></div></div>