Re: [V7, 2/2] media: i2c: dw9768: Add DW9768 VCM driver

[Dongchun Zhu <dongchun.zhu@mediatek.com>]

Hi Andy,

Thanks for the review. My replies are as below.

On Fri, 2020-06-05 at 15:46 +0300, Andy Shevchenko wrote:
> On Fri, Jun 05, 2020 at 06:54:12PM +0800, Dongchun Zhu wrote:
> > Add a V4L2 sub-device driver for DW9768 voice coil motor, providing
> > control to set the desired focus via IIC serial interface.
> 
> ...
> 
> > +config VIDEO_DW9768
> > +	tristate "DW9768 lens voice coil support"
> > +	depends on I2C && VIDEO_V4L2
> 
> No compile test?
> 

Sorry?
Kconfig here is based on the current media tree master branch.
It is also what the other similar drivers from Dongwoon do. 

> > +	depends on PM
> 
> This is very strange dependency for ordinary driver.
> 

Thanks for the reminder.
This would be removed in next release.
As dw9768_runtime_resume/suspend would be called if runtime PM is
disabled.

> > +	select MEDIA_CONTROLLER
> > +	select VIDEO_V4L2_SUBDEV_API
> > +	select V4L2_FWNODE
> 
> ...
> 
> > +/*
> > + * DW9768 requires waiting time (delay time) of t_OPR after power-up,
> > + * or in the case of PD reset taking place.
> > + */
> > +#define DW9768_T_OPR_US				1000
> > +#define DW9768_Tvib_MS_BASE10			(64 - 1)
> > +#define DW9768_AAC_MODE_DEFAULT			2
> 
> > +#define DW9768_AAC_TIME_DEFAULT			0x20
> 
> Hex? Why not decimal?
> 

There is one optional property 'dongwoon,aac-timing' defined in DT.
I don't know whether you have noticed that.

'DW9768_AAC_TIME_DEFAULT' is the value set to AACT[5:0] register.
I thought the Hex unit should be proper as it is directly written to the
Hex register.

> > +#define DW9768_CLOCK_PRE_SCALE_DEFAULT		1
> 
> ...
> 
> > +static int dw9768_mod_reg(struct dw9768 *dw9768, u8 reg, u8 mask, u8 val)
> > +{
> > +	struct i2c_client *client = v4l2_get_subdevdata(&dw9768->sd);
> > +	int ret;
> > +
> > +	ret = i2c_smbus_read_byte_data(client, reg);
> > +	if (ret < 0)
> > +		return ret;
> > +
> 
> > +	val = ((unsigned char)ret & ~mask) | (val & mask);
> 
> This cast is weird.
> 

Thanks for the review, but this cast is using classical pattern from
your suggestion on OV02A10 v5:
https://patchwork.linuxtv.org/patch/59788/

So I wonder whether it is still required to be refined currently.
Or what would it be supposed to do for the cast?

> > +
> > +	return i2c_smbus_write_byte_data(client, reg, val);
> > +}
> 
> ...
> 
> > +			dev_err(&client->dev, "%s I2C failure: %d",
> > +				__func__, ret);
> 
> One line?
> 

Splitting the sentence into two lines or not should both be okay.
Of course, I could put them in one line in next release.

> ...
> 
> > +static int dw9768_release(struct dw9768 *dw9768)
> > +{
> > +	struct i2c_client *client = v4l2_get_subdevdata(&dw9768->sd);
> > +	u32 move_delay_us = dw9768_cal_move_delay(dw9768->aac_mode,
> > +						  dw9768->clock_presc,
> > +						  dw9768->aac_timing) / 100;
> > +	int ret, val;
> > +
> > +	val = round_down(dw9768->focus->val, DW9768_MOVE_STEPS);
> > +	for ( ; val >= 0; val -= DW9768_MOVE_STEPS) {
> > +		ret = dw9768_set_dac(dw9768, val);
> > +		if (ret) {
> > +			dev_err(&client->dev, "I2C write fail: %d", ret);
> > +			return ret;
> > +		}
> > +		usleep_range(move_delay_us, move_delay_us + 1000);
> > +	}
> 
> 
> It will look more naturally in the multiplier kind of value.
> 
> 	unsigned int steps = DIV_ROUND_UP(...);
> 
> 	while (steps--) {
> 		...(..., steps * ..._MOVE_STEPS);
> 		...
> 	}
> 
> but double check arithmetics.
> 

The current coding style is actually updated with reference to your
previous comments on DW9768 v3:
https://patchwork.linuxtv.org/patch/61856/

> > +	return 0;
> > +}
> 
> 
> Also it seems we need to have writex_poll_timeout() implementation (see
> iopoll.h).
>