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

From: Tomasz Figa <tfiga@chromium.org>
To: Dongchun Zhu <dongchun.zhu@mediatek.com>
Cc: linus.walleij@linaro.org, bgolaszewski@baylibre.com,
	mchehab@kernel.org, andriy.shevchenko@linux.intel.com,
	robh+dt@kernel.org, mark.rutland@arm.com,
	sakari.ailus@linux.intel.com, drinkcat@chromium.org,
	matthias.bgg@gmail.com, bingbu.cao@intel.com,
	srv_heupstream@mediatek.com, linux-mediatek@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org, sj.huang@mediatek.com,
	linux-media@vger.kernel.org, devicetree@vger.kernel.org,
	louis.kuo@mediatek.com, shengnan.wang@mediatek.com
Subject: Re: [V7, 2/2] media: i2c: dw9768: Add DW9768 VCM driver
Date: Fri, 5 Jun 2020 13:44:40 +0000	[thread overview]
Message-ID: <20200605134440.GA20379@chromium.org> (raw)
In-Reply-To: <20200605105412.18813-3-dongchun.zhu@mediatek.com>

Hi Dongchun,

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.
> 
> Signed-off-by: Dongchun Zhu <dongchun.zhu@mediatek.com>
> ---
>  MAINTAINERS                |   1 +
>  drivers/media/i2c/Kconfig  |  13 ++
>  drivers/media/i2c/Makefile |   1 +
>  drivers/media/i2c/dw9768.c | 566 +++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 581 insertions(+)
>  create mode 100644 drivers/media/i2c/dw9768.c
> 

Thank you for the patch. Please see my comments inline.

[snip]
> +/*
> + * 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)

Kernel macro names are uppercase only.

[snip]
> +	/* Set AAC Timing */
> +	if (dw9768->aac_timing != DW9768_AAC_TIME_DEFAULT) {
> +		ret = i2c_smbus_write_byte_data(client, DW9768_AAC_TIME_REG,
> +						dw9768->aac_timing);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	move_delay_us = dw9768_cal_move_delay(dw9768->aac_mode,
> +					      dw9768->clock_presc,
> +					      dw9768->aac_timing) / 100;

We could calculate this once in probe() and store the ready us value in
the dw9768 struct.

> +
> +	for (val = dw9768->focus->val % DW9768_MOVE_STEPS;
> +	     val <= dw9768->focus->val;
> +	     val += DW9768_MOVE_STEPS) {
> +		ret = dw9768_set_dac(dw9768, val);
> +		if (ret) {
> +			dev_err(&client->dev, "%s I2C failure: %d",
> +				__func__, ret);
> +			return ret;
> +		}
> +		usleep_range(move_delay_us, move_delay_us + 1000);
> +	}
> +
> +	return 0;
> +}
[snip]
> +	pm_runtime_enable(dev);
> +	if (!pm_runtime_enabled(dev)) {
> +		ret = dw9768_runtime_resume(dev);
> +		if (ret < 0) {
> +			dev_err(dev, "failed to power on: %d\n", ret);
> +			goto err_clean_entity;
> +		}
> +	}
> +
> +	ret = v4l2_async_register_subdev(&dw9768->sd);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to register V4L2 subdev: %d", ret);
> +		goto error_async_register;
> +	}
> +
> +	return 0;
> +
> +error_async_register:

The recommendation is to name the labels after the clean-up task that needs
to be done. Should this one be called error_power_off?

> +	if (!pm_runtime_enabled(dev))
> +		dw9768_runtime_suspend(dev);

Shouldn't we also call pm_runtime_disable() here?

> +err_clean_entity:
> +	media_entity_cleanup(&dw9768->sd.entity);
> +err_free_handler:
> +	v4l2_ctrl_handler_free(&dw9768->ctrls);
> +
> +	return ret;
> +}
> +
> +static int dw9768_remove(struct i2c_client *client)
> +{
> +	struct v4l2_subdev *sd = i2c_get_clientdata(client);
> +	struct dw9768 *dw9768 = sd_to_dw9768(sd);
> +
> +	v4l2_async_unregister_subdev(&dw9768->sd);
> +	v4l2_ctrl_handler_free(&dw9768->ctrls);
> +	media_entity_cleanup(&dw9768->sd.entity);
> +	pm_runtime_disable(&client->dev);
> +	if (!pm_runtime_status_suspended(&client->dev))

pm_runtime_status_suspended() doesn't consider the runtime PM disable
state. There is also pm_runtime_suspended() and that should be correct
here.

Best regards,
Tomasz