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