media: rcar-csi2: Optimize the selection PHTW register

commit 549cc89cd09a85aaa16dc07ef3db811d5cf9bcb1 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/media/platform/rcar-vin/rcar-csi2.c b/drivers/media/platform/rcar-vin/rcar-csi2.c
index 6fb8efcb404447d6252cf787727ff60b656dbc10..5e8e48a721a049c9faabaa8c3e4d6770f99e6eaa 100644 (file)
--- a/drivers/media/platform/rcar-vin/rcar-csi2.c
+++ b/drivers/media/platform/rcar-vin/rcar-csi2.c
@@ -976,10 +976,17 @@ 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);