linux-kernel - [PATCH] drm/bridge: parade-ps8640: Fix additional suspend/resume at bootup

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Message-Id: <20211112084302.2447931-1-yangcong5@huaqin.corp-partner.google.com>
Date:   Fri, 12 Nov 2021 16:43:02 +0800
From:   yangcong <yangcong5@...qin.corp-partner.google.com>
To:     swboyd@...omium.org, robert.foss@...aro.org,
        narmstrong@...libre.com, Laurent.pinchart@...asonboard.com,
        jonas@...boo.se, jernej.skrabec@...il.com, airlied@...ux.ie,
        daniel@...ll.ch, a.hajda@...sung.com, philipchen@...omium.org,
        dianders@...gle.com
Cc:     dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        yangcong <yangcong5@...qin.corp-partner.google.com>
Subject: [PATCH] drm/bridge: parade-ps8640: Fix additional suspend/resume at bootup

Through log and waveform, we can see that there will be additional
suspend/resume when booting. This timing does not meet the ps8640 spec.
It seems that the delay of 500ms does not satisfied drm_panel_get_modes.
I increased it to 900ms and it seems that this problem can be solved.
To be safe, I'd just round up to a full 1000.

Signed-off-by: yangcong <yangcong5@...qin.corp-partner.google.com>
---
 drivers/gpu/drm/bridge/parade-ps8640.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
index 0c7aab42b04f..0749fa628bfb 100644
--- a/drivers/gpu/drm/bridge/parade-ps8640.c
+++ b/drivers/gpu/drm/bridge/parade-ps8640.c
@@ -635,13 +635,13 @@ static int ps8640_probe(struct i2c_client *client)
 	pm_runtime_enable(dev);
 	/*
 	 * Powering on ps8640 takes ~300ms. To avoid wasting time on power
-	 * cycling ps8640 too often, set autosuspend_delay to 500ms to ensure
+	 * cycling ps8640 too often, set autosuspend_delay to 1000ms to ensure
 	 * the bridge wouldn't suspend in between each _aux_transfer_msg() call
 	 * during EDID read (~20ms in my experiment) and in between the last
 	 * _aux_transfer_msg() call during EDID read and the _pre_enable() call
 	 * (~100ms in my experiment).
 	 */
-	pm_runtime_set_autosuspend_delay(dev, 500);
+	pm_runtime_set_autosuspend_delay(dev, 1000);
 	pm_runtime_use_autosuspend(dev);
 	pm_suspend_ignore_children(dev, true);
 	ret = devm_add_action_or_reset(dev, ps8640_runtime_disable, dev);
-- 
2.25.1