linux-kernel - [PATCH] rcar-vin: rcar-csi2: Select the correct PHTW register

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Date:   Wed, 27 May 2020 18:17:35 +0200
From:   Michael Rodin <mrodin@...adit-jv.com>
To:     Niklas Söderlund <niklas.soderlund@...natech.se>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        <linux-media@...r.kernel.org>, <linux-renesas-soc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Michael Rodin <mrodin@...adit-jv.com>, <michael@...in.online>,
        <efriedrich@...adit-jv.com>, <erosca@...adit-jv.com>,
        Suresh Udipi <sudipi@...adit-jv.com>
Subject: [PATCH] rcar-vin: rcar-csi2: Select the correct PHTW register

From: Suresh Udipi <sudipi@...adit-jv.com>

PHTW register is selected based on default bit rate from Table[1].
for the bit rates less than or equal to 250. Currently first
value of default bit rate which is greater than or equal to
the caculated mbps is selected.This selection can be further
improved by selecting the default bit rate which is nearest to
the calculated value.

[1] specs r19uh0105ej0200-r-car-3rd-generation.pdf [Table 25.12]

Fixes: ADIT v4.14 commit 9e568b895ee0 ("media: rcar-csi2: add Renesas R-Car MIPI CSI-2 receiver driver")

Signed-off-by: Suresh Udipi <sudipi@...adit-jv.com>
Signed-off-by: Michael Rodin <mrodin@...adit-jv.com>
---
 drivers/media/platform/rcar-vin/rcar-csi2.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/rcar-vin/rcar-csi2.c b/drivers/media/platform/rcar-vin/rcar-csi2.c
index 687baee..115b0af 100644
--- a/drivers/media/platform/rcar-vin/rcar-csi2.c
+++ b/drivers/media/platform/rcar-vin/rcar-csi2.c
@@ -886,10 +886,18 @@ static int rcsi2_phtw_write_mbps(struct rcar_csi2 *priv, unsigned int mbps,
 				 const struct rcsi2_mbps_reg *values, u16 code)
 {
 	const struct rcsi2_mbps_reg *value;
+	const struct rcsi2_mbps_reg *prev_value = NULL;
 
-	for (value = values; value->mbps; value++)
+	for (value = values; value->mbps; value++) {
 		if (value->mbps >= mbps)
 			break;
+		prev_value = value;
+	}
+
+	if (prev_value &&
+	    ((mbps - prev_value->mbps) <= (value->mbps - mbps)))
+		value = prev_value;
+
 
 	if (!value->mbps) {
 		dev_err(priv->dev, "Unsupported PHY speed (%u Mbps)", mbps);
-- 
2.7.4