linux-kernel - [PATCH] [RFC] media: rcar-vin: don't wait for stop state on clock lane during start of CSI2

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Message-ID: <1582026251-21047-1-git-send-email-mrodin@de.adit-jv.com>
Date:   Tue, 18 Feb 2020 12:44:11 +0100
From:   Michael Rodin <mrodin@...adit-jv.com>
To:     <niklas.soderlund@...natech.se>, <mchehab@...nel.org>,
        <p.zabel@...gutronix.de>, <linux-media@...r.kernel.org>,
        <linux-renesas-soc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     Michael Rodin <mrodin@...adit-jv.com>, <efriedrich@...adit-jv.com>,
        <erosca@...adit-jv.com>, <sudipi@...adit-jv.com>,
        <akiyama@...-osk.co.jp>
Subject: [PATCH] [RFC] media: rcar-vin: don't wait for stop state on clock lane during start of CSI2

The chapter 7.1 "D-PHY Physical Layer Option" of the CSI2 specification
states that non-continuous clock behavior is optional, i.e. the Clock Lane
can remain in high-speed mode between the transmission of data packets.
Therefore waiting for the stop state (LP-11) on the Clock Lane is wrong and
will cause timeouts when a CSI2 transmitter with continuous clock behavior
is attached to R-Car CSI2 receiver. So wait only for the stop state on the
Data Lanes.

Signed-off-by: Michael Rodin <mrodin@...adit-jv.com>
---
 drivers/media/platform/rcar-vin/rcar-csi2.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/media/platform/rcar-vin/rcar-csi2.c b/drivers/media/platform/rcar-vin/rcar-csi2.c
index faa9fb2..6d1992a 100644
--- a/drivers/media/platform/rcar-vin/rcar-csi2.c
+++ b/drivers/media/platform/rcar-vin/rcar-csi2.c
@@ -416,8 +416,7 @@ static int rcsi2_wait_phy_start(struct rcar_csi2 *priv)
 	for (timeout = 0; timeout <= 20; timeout++) {
 		const u32 lane_mask = (1 << priv->lanes) - 1;
 
-		if ((rcsi2_read(priv, PHCLM_REG) & PHCLM_STOPSTATECKL)  &&
-		    (rcsi2_read(priv, PHDLM_REG) & lane_mask) == lane_mask)
+		if ((rcsi2_read(priv, PHDLM_REG) & lane_mask) == lane_mask)
 			return 0;
 
 		usleep_range(1000, 2000);
-- 
2.7.4