Commit bf1178c9 authored Aug 13, 2018 by Sean Paul

drm/bridge: ti-sn65dsi86: Add mystery delay to enable()



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>
Reviewed-by: Sandeep Panda <spanda@codeaurora.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180813213058.184821-8-sean@poorly.run

parent bc537a9c

drivers/gpu/drm/bridge/ti-sn65dsi86.c

+12 −0

Original line number	Diff line number	Diff line
		@@ -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.
		*/
		msleep(70);

		/* DSI_A lane config */
		val = CHA_DSI_LANES(4 - pdata->dsi->lanes);
		regmap_update_bits(pdata->regmap, SN_DSI_LANES_REG,