Re: [PATCH 3/4] media: ov5647: Add support for non-continuous clock mode

From: Jacopo Mondi
Date: Wed Apr 15 2020 - 09:16:25 EST


Hi Roman,

On Mon, Apr 13, 2020 at 12:17:46PM +0300, Roman Kovalivskyi wrote:
> From: Dave Stevenson <dave.stevenson@xxxxxxxxxxxxxxx>
>
> The driver was only supporting continuous clock mode
> although this was not stated anywhere.
> Non-continuous clock saves a small amount of power and
> on some SoCs is easier to interface with.

As per the previous patch, you should update bindings reporting this
property is now optionally supported

>
> Signed-off-by: Dave Stevenson <dave.stevenson@xxxxxxxxxxxxxxx>
> Signed-off-by: Roman Kovalivskyi <roman.kovalivskyi@xxxxxxxxxxxxxxx>
> ---
> drivers/media/i2c/ov5647.c | 17 ++++++++++++++---
> 1 file changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/media/i2c/ov5647.c b/drivers/media/i2c/ov5647.c
> index c39e3d20e3ef..8a1a515388e0 100644
> --- a/drivers/media/i2c/ov5647.c
> +++ b/drivers/media/i2c/ov5647.c
> @@ -44,6 +44,7 @@
> #define PWDN_ACTIVE_DELAY_MS 20
>
> #define MIPI_CTRL00_CLOCK_LANE_GATE BIT(5)
> +#define MIPI_CTRL00_LINE_SYNC_ENABLE BIT(4)
> #define MIPI_CTRL00_BUS_IDLE BIT(2)
> #define MIPI_CTRL00_CLOCK_LANE_DISABLE BIT(0)
>
> @@ -95,6 +96,7 @@ struct ov5647 {
> int power_count;
> struct clk *xclk;
> struct gpio_desc *pwdn;
> + unsigned int flags;
> };
>
> static inline struct ov5647 *to_state(struct v4l2_subdev *sd)
> @@ -269,9 +271,15 @@ static int ov5647_set_virtual_channel(struct v4l2_subdev *sd, int channel)
>
> static int ov5647_stream_on(struct v4l2_subdev *sd)
> {
> + struct ov5647 *ov5647 = to_state(sd);
> + u8 val = MIPI_CTRL00_BUS_IDLE;
> int ret;
>
> - ret = ov5647_write(sd, OV5647_REG_MIPI_CTRL00, MIPI_CTRL00_BUS_IDLE);
> + if (ov5647->flags & V4L2_MBUS_CSI2_NONCONTINUOUS_CLOCK)
> + val |= MIPI_CTRL00_CLOCK_LANE_GATE |
> + MIPI_CTRL00_LINE_SYNC_ENABLE;
> +
> + ret = ov5647_write(sd, OV5647_REG_MIPI_CTRL00, val);
> if (ret < 0)
> return ret;
>
> @@ -568,7 +576,7 @@ static const struct v4l2_subdev_internal_ops ov5647_subdev_internal_ops = {
> .open = ov5647_open,
> };
>
> -static int ov5647_parse_dt(struct device_node *np)
> +static int ov5647_parse_dt(struct device_node *np, struct ov5647 *sensor)

nit: I would provide the driver structure first

> {
> struct v4l2_fwnode_endpoint bus_cfg = { .bus_type = 0 };
> struct device_node *ep;
> @@ -581,6 +589,9 @@ static int ov5647_parse_dt(struct device_node *np)
>
> ret = v4l2_fwnode_endpoint_parse(of_fwnode_handle(ep), &bus_cfg);
>
> + if (!ret)
> + sensor->flags = bus_cfg.bus.mipi_csi2.flags;
> +

There is a huge space for improvements here, this function didn't do
anything before this.

I would:
check the v4l2_fwnode_endpoint_parse() return value, and
put(np) and fail loudly

make sure the detected bus type is CSI-2

cache the flags as you're doing here. As you're only
interested in clock continuous you could store only that
information in your driver structure.

> of_node_put(ep);
> return ret;
> }
> @@ -599,7 +610,7 @@ static int ov5647_probe(struct i2c_client *client)
> return -ENOMEM;
>
> if (IS_ENABLED(CONFIG_OF) && np) {
> - ret = ov5647_parse_dt(np);
> + ret = ov5647_parse_dt(np, sensor);
> if (ret) {
> dev_err(dev, "DT parsing error: %d\n", ret);
> return ret;
> --
> 2.17.1
>