From 549cc89cd09a85aaa16dc07ef3db811d5cf9bcb1 Mon Sep 17 00:00:00 2001
From: Suresh Udipi <sudipi@jp.adit-jv.com>
Date: Fri, 13 Aug 2021 17:07:56 +0200
Subject: [PATCH] media: rcar-csi2: Optimize the selection PHTW register
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Git-commit: 549cc89cd09a85aaa16dc07ef3db811d5cf9bcb1
Patch-mainline: v5.17-rc1
References: git-fixes

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: 769afd212b16 ("media: rcar-csi2: add Renesas R-Car MIPI CSI-2 receiver driver")
Signed-off-by: Suresh Udipi <sudipi@jp.adit-jv.com>
Signed-off-by: Michael Rodin <mrodin@de.adit-jv.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/media/platform/rcar-vin/rcar-csi2.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/rcar-vin/rcar-csi2.c b/drivers/media/platform/rcar-vin/rcar-csi2.c
index db119a002414..e2c4ab69a477 100644
--- a/drivers/media/platform/rcar-vin/rcar-csi2.c
+++ b/drivers/media/platform/rcar-vin/rcar-csi2.c
@@ -1108,10 +1108,17 @@ 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);
-- 
2.31.1