linux-kernel - [PATCH v2] drm/bridge: Add 200ms delay to wait FW HPD status stable

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Date:   Fri, 22 Sep 2023 17:34:49 +0800
From:   Xin Ji <xji@...logixsemi.com>
To:     Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     bliang@...logixsemi.com, qwen@...logixsemi.com,
        hsinyi@...omium.org, Xin Ji <xji@...logixsemi.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] drm/bridge: Add 200ms delay to wait FW HPD status stable

For the no-interrupt design (sink device is panel, polling HPD
status when chip power on), anx7625 FW has more than 200ms HPD
de-bounce time in FW, for the safety to get HPD status, driver
better to wait 200ms before HPD detection after OS resume back.

Signed-off-by: Xin Ji <xji@...logixsemi.com>
---
 drivers/gpu/drm/bridge/analogix/anx7625.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/bridge/analogix/anx7625.c b/drivers/gpu/drm/bridge/analogix/anx7625.c
index 51abe42c639e..8f740154707d 100644
--- a/drivers/gpu/drm/bridge/analogix/anx7625.c
+++ b/drivers/gpu/drm/bridge/analogix/anx7625.c
@@ -1464,6 +1464,9 @@ static int _anx7625_hpd_polling(struct anx7625_data *ctx,
 	if (ctx->pdata.intp_irq)
 		return 0;
 
+	/* Delay 200ms for FW HPD de-bounce */
+	msleep(200);
+
 	ret = readx_poll_timeout(anx7625_read_hpd_status_p0,
 				 ctx, val,
 				 ((val & HPD_STATUS) || (val < 0)),
-- 
2.25.1