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

Dongchun Zhu
2020-06-06T06:45:22Z

Hi Tomasz,

Thanks for the review.

On Fri, 2020-06-05 at 13:44 +0000, Tomasz Figa wrote:
> 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.
>

Aha... This is caused by my carelessness.
Fixed in next release.

> [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.
>

Great idea :-)
From the perspective of 'move_delay_us' itself, it defines VCM Operation
Time, which is indeed an intrinsic parameter that belongs to DW9768
private structure.

> > +
> > + 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?
>

Understood.
'error_async_register' would be replaced of 'err_power_off' in next
release.

> > + if (!pm_runtime_enabled(dev))
> > + dw9768_runtime_suspend(dev);
>
> Shouldn't we also call pm_runtime_disable() here?
>

Thanks for the reminder.
We would add pm_runtime_disable() in next release.
Just like:
err_power_off:
pm_runtime_disable(dev);
if (!pm_runtime_enabled(dev))
dw9768_runtime_suspend(dev);

> > +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.
>

Fixed in next release.

> Best regards,
> Tomasz