From: Sean Paul Date: Mon, 13 Aug 2018 21:30:46 +0000 (-0400) Subject: drm/bridge: ti-sn65dsi86: Add mystery delay to enable() X-Git-Tag: v4.20-rc1~21^2~33^2~55 X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=bf1178c9893018b77c829215970cf4c6a3cebb34;p=uclinux-h8%2Flinux.git 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 Reviewed-by: Sandeep Panda Signed-off-by: Sean Paul Link: https://patchwork.freedesktop.org/patch/msgid/20180813213058.184821-8-sean@poorly.run --- diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c index d3e27e52ea75..f8a931cf3665 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. + */ + msleep(70); + /* DSI_A lane config */ val = CHA_DSI_LANES(4 - pdata->dsi->lanes); regmap_update_bits(pdata->regmap, SN_DSI_LANES_REG,