[PATCH 5.15 163/846] media: rcar-csi2: Correct the selection of hsfreqrange

[Greg Kroah-Hartman]

From: Suresh Udipi <sudipi@xxxxxxxxxxxxxx>

[ Upstream commit cee44d4fbacbbdfe62697ec94e76c6e4f726c5df ]

hsfreqrange should be chosen based on the calculated mbps which
is closer to the default bit rate  and within the range as per
table[1]. But current calculation always selects first value which
is greater than or equal to the calculated mbps which may lead
to chosing a wrong range in some cases.

For example for 360 mbps for H3/M3N
Existing logic selects
Calculated value 360Mbps : Default 400Mbps Range [368.125 -433.125 mbps]

This hsfreqrange is out of range.

The logic is changed to get the default value which is closest to the
calculated value [1]

Calculated value 360Mbps : Default 350Mbps  Range [320.625 -380.625 mpbs]

[1] specs r19uh0105ej0200-r-car-3rd-generation.pdf [Table 25.9]

Please note that According to Renesas in Table 25.9 the range for
220 default value is corrected as below

 |Range (Mbps)     |  Default  Bit rate (Mbps) |
 -----------------------------------------------
 | 197.125-244.125 |     220                   |
 -----------------------------------------------

Fixes: 769afd212b16 ("media: rcar-csi2: add Renesas R-Car MIPI CSI-2 receiver driver")
Signed-off-by: Suresh Udipi <sudipi@xxxxxxxxxxxxxx>
Signed-off-by: Kazuyoshi Akiyama <akiyama@xxxxxxxxxxxxx>
Signed-off-by: Michael Rodin <mrodin@xxxxxxxxxxxxxx>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 ba4a380016cc4..3de782a908659 100644
--- a/drivers/media/platform/rcar-vin/rcar-csi2.c
+++ b/drivers/media/platform/rcar-vin/rcar-csi2.c
@@ -445,16 +445,23 @@ static int rcsi2_wait_phy_start(struct rcar_csi2 *priv,
 static int rcsi2_set_phypll(struct rcar_csi2 *priv, unsigned int mbps)
 {
 	const struct rcsi2_mbps_reg *hsfreq;
+	const struct rcsi2_mbps_reg *hsfreq_prev = NULL;
 
-	for (hsfreq = priv->info->hsfreqrange; hsfreq->mbps != 0; hsfreq++)
+	for (hsfreq = priv->info->hsfreqrange; hsfreq->mbps != 0; hsfreq++) {
 		if (hsfreq->mbps >= mbps)
 			break;
+		hsfreq_prev = hsfreq;
+	}
 
 	if (!hsfreq->mbps) {
 		dev_err(priv->dev, "Unsupported PHY speed (%u Mbps)", mbps);
 		return -ERANGE;
 	}
 
+	if (hsfreq_prev &&
+	    ((mbps - hsfreq_prev->mbps) <= (hsfreq->mbps - mbps)))
+		hsfreq = hsfreq_prev;
+
 	rcsi2_write(priv, PHYPLL_REG, PHYPLL_HSFREQRANGE(hsfreq->reg));
 
 	return 0;
-- 
2.34.1