Hi Jacopo
On Wed, 5 Oct 2022 at 20:07, Jacopo Mondi <jacopo@xxxxxxxxxx> wrote:
>
> Add support for V4L2_CID_ANALOG_GAIN. The control programs the global
> gain register which applies to all color channels.
>
> As both the global digital and analog gains are controlled through a
> single register, in order not to overwrite the configured digital gain
> we need to read the current register value before modifying it.
>
> Implement a function to read register values and use it before applying
> the new analog gain.
>
> Signed-off-by: Jacopo Mondi <jacopo@xxxxxxxxxx>
> ---
> drivers/media/i2c/ar0521.c | 64 ++++++++++++++++++++++++++++++++++++++
> 1 file changed, 64 insertions(+)
>
> diff --git a/drivers/media/i2c/ar0521.c b/drivers/media/i2c/ar0521.c
> index 89f3c01f18ce..581f5e42994d 100644
> --- a/drivers/media/i2c/ar0521.c
> +++ b/drivers/media/i2c/ar0521.c
> @@ -5,6 +5,8 @@
> * Written by Krzysztof Hałasa
> */
>
> +#include <asm/unaligned.h>
> +
> #include <linux/clk.h>
> #include <linux/delay.h>
> #include <linux/pm_runtime.h>
> @@ -35,6 +37,11 @@
> #define AR0521_HEIGHT_BLANKING_MIN 38u /* must be even */
> #define AR0521_TOTAL_WIDTH_MIN 2968u
>
> +#define AR0521_ANA_GAIN_MIN 0x00
> +#define AR0521_ANA_GAIN_MAX 0x3f
> +#define AR0521_ANA_GAIN_STEP 0x01
> +#define AR0521_ANA_GAIN_DEFAULT 0x00
> +
> /* AR0521 registers */
> #define AR0521_REG_VT_PIX_CLK_DIV 0x0300
> #define AR0521_REG_FRAME_LENGTH_LINES 0x0340
> @@ -55,6 +62,7 @@
> #define AR0521_REG_RED_GAIN 0x305A
> #define AR0521_REG_GREEN2_GAIN 0x305C
> #define AR0521_REG_GLOBAL_GAIN 0x305E
> +#define AR0521_REG_GLOBAL_GAIN_ANA_MASK 0x3f
>
> #define AR0521_REG_HISPI_TEST_MODE 0x3066
> #define AR0521_REG_HISPI_TEST_MODE_LP11 0x0004
> @@ -77,6 +85,7 @@ static const char * const ar0521_supply_names[] = {
>
> struct ar0521_ctrls {
> struct v4l2_ctrl_handler handler;
> + struct v4l2_ctrl *ana_gain;
> struct {
> struct v4l2_ctrl *gain;
> struct v4l2_ctrl *red_balance;
> @@ -167,6 +176,36 @@ static int ar0521_write_reg(struct ar0521_dev *sensor, u16 reg, u16 val)
> return ar0521_write_regs(sensor, buf, 2);
> }
>
> +static int ar0521_read_reg(struct ar0521_dev *sensor, u16 reg, u16 *val)
> +{
> + struct i2c_client *client = sensor->i2c_client;
> + unsigned char buf[2];
> + struct i2c_msg msg;
> + int ret;
> +
> + msg.addr = client->addr;
> + msg.flags = client->flags;
> + msg.len = sizeof(u16);
> + msg.buf = buf;
> + put_unaligned_be16(reg, buf);
> +
> + ret = i2c_transfer(client->adapter, &msg, 1);
> + if (ret < 0)
> + return ret;
> +
> + msg.len = sizeof(u16);
> + msg.flags = client->flags | I2C_M_RD;
> + msg.buf = buf;
> +
> + ret = i2c_transfer(client->adapter, &msg, 1);
> + if (ret < 0)
> + return ret;
> +
> + *val = get_unaligned_be16(buf);
> +
> + return 0;
> +}
> +
> static int ar0521_set_geometry(struct ar0521_dev *sensor)
> {
> /* All dimensions are unsigned 12-bit integers */
> @@ -187,6 +226,21 @@ static int ar0521_set_geometry(struct ar0521_dev *sensor)
> return ar0521_write_regs(sensor, regs, ARRAY_SIZE(regs));
> }
>
> +static int ar0521_set_analog_gain(struct ar0521_dev *sensor)
> +{
> + u16 global_gain;
> + int ret;
> +
> + ret = ar0521_read_reg(sensor, AR0521_REG_GLOBAL_GAIN, &global_gain);
> + if (ret)
> + return ret;
> +
> + global_gain &= ~AR0521_REG_GLOBAL_GAIN_ANA_MASK;
> + global_gain |= sensor->ctrls.ana_gain->val & AR0521_REG_GLOBAL_GAIN_ANA_MASK;
> +
> + return ar0521_write_reg(sensor, AR0521_REG_GLOBAL_GAIN, global_gain);
Does this work without nasty interactions?
The register reference I have says that the bits 6:0 of 0x3056,
0x3058, 0x305a, 0x305c, and 0x305e are all aliased to register 0x3056.
That means that the writes from ar0521_set_gains for GAIN,
RED_BALANCE, and BLUE_BALANCE will stomp over your ANALOGUE_GAIN.
I also don't see a call to __v4l2_ctrl_handler_setup from
ar0521_set_stream, so whilst there is an explicit call to
ar0521_set_gains, ANALOGUE_GAIN won't be set.
Dave
[1] https://github.com/torvalds/linux/blob/master/drivers/media/i2c/ar0521.c#L190
> +}
> +
> static int ar0521_set_gains(struct ar0521_dev *sensor)
> {
> int green = sensor->ctrls.gain->val;
> @@ -456,6 +510,9 @@ static int ar0521_s_ctrl(struct v4l2_ctrl *ctrl)
> case V4L2_CID_VBLANK:
> ret = ar0521_set_geometry(sensor);
> break;
> + case V4L2_CID_ANALOGUE_GAIN:
> + ret = ar0521_set_analog_gain(sensor);
> + break;
> case V4L2_CID_GAIN:
> case V4L2_CID_RED_BALANCE:
> case V4L2_CID_BLUE_BALANCE:
> @@ -499,6 +556,13 @@ static int ar0521_init_controls(struct ar0521_dev *sensor)
> /* We can use our own mutex for the ctrl lock */
> hdl->lock = &sensor->lock;
>
> + /* Analog gain */
> + ctrls->ana_gain = v4l2_ctrl_new_std(hdl, ops, V4L2_CID_ANALOGUE_GAIN,
> + AR0521_ANA_GAIN_MIN,
> + AR0521_ANA_GAIN_MAX,
> + AR0521_ANA_GAIN_STEP,
> + AR0521_ANA_GAIN_DEFAULT);
> +
> /* Manual gain */
> ctrls->gain = v4l2_ctrl_new_std(hdl, ops, V4L2_CID_GAIN, 0, 511, 1, 0);
> ctrls->red_balance = v4l2_ctrl_new_std(hdl, ops, V4L2_CID_RED_BALANCE,
> --
> 2.37.3
>
