diff options
Diffstat (limited to 'drivers/gpu/drm/bridge')
-rw-r--r-- | drivers/gpu/drm/bridge/ti-sn65dsi86.c | 29 |
1 files changed, 16 insertions, 13 deletions
diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c index f8a931cf3665..680566d97adc 100644 --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c @@ -458,18 +458,6 @@ 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, @@ -536,7 +524,22 @@ static void ti_sn_bridge_pre_enable(struct drm_bridge *bridge) /* configure bridge ref_clk */ ti_sn_bridge_set_refclk_freq(pdata); - /* in case drm_panel is connected then HPD is not supported */ + /* + * HPD on this bridge chip is a bit useless. This is an eDP bridge + * so the HPD is an internal signal that's only there to signal that + * the panel is done powering up. ...but the bridge chip debounces + * this signal by between 100 ms and 400 ms (depending on process, + * voltage, and temperate--I measured it at about 200 ms). One + * particular panel asserted HPD 84 ms after it was powered on meaning + * that we saw HPD 284 ms after power on. ...but the same panel said + * that instead of looking at HPD you could just hardcode a delay of + * 200 ms. We'll assume that the panel driver will have the hardcoded + * delay in its prepare and always disable HPD. + * + * If HPD somehow makes sense on some future panel we'll have to + * change this to be conditional on someone specifying that HPD should + * be used. + */ regmap_update_bits(pdata->regmap, SN_HPD_DISABLE_REG, HPD_DISABLE, HPD_DISABLE); |