RE: [PATCH v2] dw9714: Initial driver for dw9714 VCM

["Mani, Rajmohan" <rajmohan.mani@intel.com>]

Hi Tomasz,
Thanks for the reviews. Please see comments inline.

> -----Original Message-----
> From: Tomasz Figa [mailto:tfiga@chromium.org]
> Sent: Tuesday, May 09, 2017 4:44 PM
> To: Mani, Rajmohan <rajmohan.mani@intel.com>
> Cc: linux-media@vger.kernel.org; mchehab@kernel.org; Hans Verkuil
> <hverkuil@xs4all.nl>
> Subject: Re: [PATCH v2] dw9714: Initial driver for dw9714 VCM
> 
> Hi Rajmohan,
> 
> Some comments below.
> 
> On Mon, May 8, 2017 at 10:36 PM, Rajmohan Mani
> <rajmohan.mani@intel.com> wrote:
> > DW9714 is a 10 bit DAC, designed for linear control of voice coil
> > motor.
> >
> > This driver creates a V4L2 subdevice and provides control to set the
> > desired focus.
> >
> > Signed-off-by: Rajmohan Mani <rajmohan.mani@intel.com>
> > ---
> > Changes in v2:
> >         - Addressed review comments from Hans Verkuil
> >         - Fixed a debug message typo
> >         - Got rid of a return variable
> > ---
> >  drivers/media/i2c/Kconfig  |   9 ++
> >  drivers/media/i2c/Makefile |   1 +
> >  drivers/media/i2c/dw9714.c | 320
> > +++++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 330 insertions(+)
> >  create mode 100644 drivers/media/i2c/dw9714.c
> [snip]
> > diff --git a/drivers/media/i2c/dw9714.c b/drivers/media/i2c/dw9714.c
> > new file mode 100644 index 0000000..cd6cde7
> > --- /dev/null
> > +++ b/drivers/media/i2c/dw9714.c
> > @@ -0,0 +1,320 @@
> > +/*
> > + * Copyright (c) 2015--2017 Intel Corporation.
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License
> > +version
> > + * 2 as published by the Free Software Foundation.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.
> > + */
> > +
> > +#include <linux/acpi.h>
> > +#include <linux/delay.h>
> > +#include <linux/i2c.h>
> > +#include <linux/module.h>
> > +#include <linux/pm_runtime.h>
> > +#include <media/v4l2-ctrls.h>
> > +#include <media/v4l2-device.h>
> > +
> > +#define DW9714_NAME            "dw9714"
> > +#define DW9714_MAX_FOCUS_POS   1023
> > +#define DW9714_CTRL_STEPS      16      /* Keep this value power of 2 */
> 
> Because?
> 

This acts as the minimum granularity of lens movement.
Keep this value power of 2, so the control steps can be uniformly adjusted for gradual lens movement, with desired number of control steps.

> > +#define DW9714_CTRL_DELAY_US   1000
> > +/*
> > + * S[3:2] = 0x00, codes per step for "Linear Slope Control"
> > + * S[1:0] = 0x00, step period
> > + */
> > +#define DW9714_DEFAULT_S 0x0
> > +#define DW9714_VAL(data, s) (u16)((data) << 4 | (s))
> 
> Do we need this cast?
> 
Yes. This is a write to a 2 byte register

> > +
> > +/* dw9714 device structure */
> > +struct dw9714_device {
> > +       struct i2c_client *client;
> > +       struct v4l2_ctrl_handler ctrls_vcm;
> > +       struct v4l2_subdev sd;
> > +       u16 current_val;
> > +};
> > +
> > +#define to_dw9714_vcm(_ctrl)   \
> > +       container_of(_ctrl->handler, struct dw9714_device, ctrls_vcm)
> 
> Please use a static inline function for type safety.
> 

Ack

> > +
> > +static int dw9714_i2c_write(struct i2c_client *client, u16 data) {
> > +       const int num_msg = 1;
> > +       int ret;
> > +       u16 val = cpu_to_be16(data);
> > +       struct i2c_msg msg = {
> > +               .addr = client->addr,
> > +               .flags = 0,
> > +               .len = sizeof(val),
> > +               .buf = (u8 *) &val,
> > +       };
> > +
> > +       ret = i2c_transfer(client->adapter, &msg, num_msg);
> > +
> > +       /*One retry */
> > +       if (ret != num_msg)
> > +               ret = i2c_transfer(client->adapter, &msg, num_msg);
> > +
> > +       if (ret != num_msg) {
> > +               dev_err(&client->dev, "I2C write fail\n");
> > +               return -EIO;
> > +       }
> 
> I believe i2c_master_send() would simplify this function significantly.
> 

Ack

> > +       return 0;
> > +}
> > +
> > +static int dw9714_t_focus_vcm(struct dw9714_device *dw9714_dev, u16
> > +val) {
> > +       struct i2c_client *client = dw9714_dev->client;
> > +
> > +       dev_dbg(&client->dev, "Setting new value VCM: %d\n", val);
> > +       dw9714_dev->current_val = val;
> > +
> > +       return dw9714_i2c_write(client, DW9714_VAL(val,
> > +DW9714_DEFAULT_S)); }
> > +
> > +static int dw9714_set_ctrl(struct v4l2_ctrl *ctrl) {
> > +       struct dw9714_device *dev_vcm = to_dw9714_vcm(ctrl);
> > +
> > +       if (ctrl->id == V4L2_CID_FOCUS_ABSOLUTE)
> > +               return dw9714_t_focus_vcm(dev_vcm, ctrl->val);
> > +
> > +       return -EINVAL;
> > +}
> > +
> > +static const struct v4l2_ctrl_ops dw9714_vcm_ctrl_ops = {
> > +       .s_ctrl = dw9714_set_ctrl,
> > +};
> > +
> > +static int dw9714_init_controls(struct dw9714_device *dev_vcm) {
> > +       struct v4l2_ctrl_handler *hdl = &dev_vcm->ctrls_vcm;
> > +       const struct v4l2_ctrl_ops *ops = &dw9714_vcm_ctrl_ops;
> > +       struct i2c_client *client = dev_vcm->client;
> > +
> > +       v4l2_ctrl_handler_init(hdl, 1);
> > +
> > +       v4l2_ctrl_new_std(hdl, ops, V4L2_CID_FOCUS_ABSOLUTE,
> > +                         0, DW9714_MAX_FOCUS_POS, 1, 0);
> > +
> > +       if (hdl->error)
> > +               dev_err(&client->dev, "dw9714_init_controls fail\n");
> > +       dev_vcm->sd.ctrl_handler = hdl;
> > +       return hdl->error;
> > +}
> > +
> > +static void dw9714_subdev_cleanup(struct dw9714_device *dw9714_dev) {
> > +       v4l2_ctrl_handler_free(&dw9714_dev->ctrls_vcm);
> > +       v4l2_async_unregister_subdev(&dw9714_dev->sd);
> > +       v4l2_device_unregister_subdev(&dw9714_dev->sd);
> > +       media_entity_cleanup(&dw9714_dev->sd.entity);
> > +}
> > +
> > +static int dw9714_open(struct v4l2_subdev *sd, struct v4l2_subdev_fh
> > +*fh) {
> > +       struct dw9714_device *dw9714_dev = container_of(sd,
> > +                                                       struct dw9714_device,
> > +                                                       sd);
> > +       struct device *dev = &dw9714_dev->client->dev;
> > +
> > +       return pm_runtime_get_sync(dev);
> 
> Need pm_runtime_put() if this fails.
> 

Ack. This is addressed in v3 of this patch.

> > +}
> > +
> > +static int dw9714_close(struct v4l2_subdev *sd, struct v4l2_subdev_fh
> > +*fh) {
> > +       struct dw9714_device *dw9714_dev = container_of(sd,
> > +                                                       struct dw9714_device,
> > +                                                       sd);
> > +       struct device *dev = &dw9714_dev->client->dev;
> > +
> > +       pm_runtime_put(dev);
> > +
> > +       return 0;
> > +}
> > +
> > +static const struct v4l2_subdev_internal_ops dw9714_int_ops = {
> > +       .open = dw9714_open,
> > +       .close = dw9714_close,
> > +};
> > +
> > +static const struct v4l2_subdev_ops dw9714_ops = { };
> > +
> > +static int dw9714_probe(struct i2c_client *client,
> > +                       const struct i2c_device_id *devid) {
> > +       struct dw9714_device *dw9714_dev;
> > +       int rval;
> > +
> > +       dw9714_dev = devm_kzalloc(&client->dev, sizeof(*dw9714_dev),
> > +                                 GFP_KERNEL);
> > +
> > +       if (dw9714_dev == NULL)
> > +               return -ENOMEM;
> > +
> > +       dw9714_dev->client = client;
> > +
> > +       v4l2_i2c_subdev_init(&dw9714_dev->sd, client, &dw9714_ops);
> > +       dw9714_dev->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
> > +       dw9714_dev->sd.internal_ops = &dw9714_int_ops;
> > +
> > +       rval = dw9714_init_controls(dw9714_dev);
> > +       if (rval)
> > +               goto err_cleanup;
> > +
> > +       rval = media_entity_pads_init(&dw9714_dev->sd.entity, 0, NULL);
> > +       if (rval < 0)
> > +               goto err_cleanup;
> > +
> > +       dw9714_dev->sd.entity.function = MEDIA_ENT_F_LENS;
> > +
> > +       rval = v4l2_async_register_subdev(&dw9714_dev->sd);
> > +       if (rval < 0)
> > +               goto err_cleanup;
> > +
> > +       pm_runtime_enable(&client->dev);
> > +
> > +       return 0;
> > +
> > +err_cleanup:
> > +       dw9714_subdev_cleanup(dw9714_dev);
> > +       dev_err(&client->dev, "Probe failed: %d\n", rval);
> > +       return rval;
> > +}
> > +
> > +static int dw9714_remove(struct i2c_client *client) {
> > +       struct v4l2_subdev *sd = i2c_get_clientdata(client);
> > +       struct dw9714_device *dw9714_dev = container_of(sd,
> > +                                                       struct dw9714_device,
> > +                                                       sd);
> > +
> > +       pm_runtime_disable(&client->dev);
> > +       dw9714_subdev_cleanup(dw9714_dev);
> > +
> > +       return 0;
> > +}
> > +
> > +#ifdef CONFIG_PM
> > +
> > +static int dw9714_runtime_suspend(struct device *dev) {
> > +       return 0;
> > +}
> > +
> > +static int dw9714_runtime_resume(struct device *dev) {
> > +       return 0;
> > +}
> > +
> > +/* This function sets the vcm position, so it consumes least current
> > +*/ static int dw9714_suspend(struct device *dev) {
> > +       struct i2c_client *client = to_i2c_client(dev);
> > +       struct v4l2_subdev *sd = i2c_get_clientdata(client);
> > +       struct dw9714_device *dw9714_dev = container_of(sd,
> > +                                                       struct dw9714_device,
> > +                                                       sd);
> > +       int ret, val;
> > +
> > +       dev_dbg(dev, "%s\n", __func__);
> > +
> > +       for (val = dw9714_dev->current_val & ~(DW9714_CTRL_STEPS - 1);
> > +            val >= 0; val -= DW9714_CTRL_STEPS) {
> > +               ret = dw9714_i2c_write(client,
> > +                                      DW9714_VAL((u16) val, DW9714_DEFAULT_S));
> > +               if (ret)
> > +                       dev_err(dev, "%s I2C failure: %d", __func__, ret);
> > +               usleep_range(DW9714_CTRL_DELAY_US,
> > + DW9714_CTRL_DELAY_US + 10);
> 
> Is it necessary to change the value in such steps? If so, shouldn't the control
> handler behave in the same way, making sure that userspace does not request
> changes in bigger steps?
> 
Ack
I will modify the ctrl handler steps to reflect this.

> > +       }
> > +       return 0;
> > +}
> > +
> > +/*
> > + * This function sets the vcm position, so the focus position is set
> > + * closer to the camera
> 
> I think it should only set the VCM position to the value as set before the
> suspend.
> 

Ack
The code already does it. I will fix the comments.

> > + */
> > +static int dw9714_resume(struct device *dev) {
> > +       struct i2c_client *client = to_i2c_client(dev);
> > +       struct v4l2_subdev *sd = i2c_get_clientdata(client);
> > +       struct dw9714_device *dw9714_dev = container_of(sd,
> > +                                                       struct dw9714_device,
> > +                                                       sd);
> > +       int ret, val;
> > +
> > +       dev_dbg(dev, "%s\n", __func__);
> > +
> > +       for (val = dw9714_dev->current_val % DW9714_CTRL_STEPS;
> > +            val < dw9714_dev->current_val + DW9714_CTRL_STEPS - 1;
> > +            val += DW9714_CTRL_STEPS) {
> > +               ret = dw9714_i2c_write(client,
> > +                                      DW9714_VAL((u16) val, DW9714_DEFAULT_S));
> > +               if (ret)
> > +                       dev_err(dev, "%s I2C failure: %d", __func__, ret);
> > +               usleep_range(DW9714_CTRL_DELAY_US, DW9714_CTRL_DELAY_US
> + 10);
> > +       }
> > +
> > +       /* restore v4l2 control values */
> > +       ret = v4l2_ctrl_handler_setup(&dw9714_dev->ctrls_vcm);
> > +       dev_dbg(dev, "%s ret = %d\n", __func__, ret);
> > +       return ret;
> > +}
> > +
> > +#else
> > +
> > +#define dw9714_suspend NULL
> > +#define dw9714_resume  NULL
> > +#define dw9714_runtime_suspend NULL
> > +#define dw9714_runtime_resume  NULL
> 
> This #define trickery shouldn't be necessary. Please see below.
> (#ifndef/#endif around the functions themselves is still necessary.)
> 

Ack

> > +
> > +#endif /* CONFIG_PM */
> > +
> > +#ifdef CONFIG_ACPI
> > +static const struct acpi_device_id dw9714_acpi_match[] = {
> > +       {"DW9714", 0},
> > +       {},
> > +};
> > +MODULE_DEVICE_TABLE(acpi, dw9714_acpi_match); #endif
> > +
> > +static const struct i2c_device_id dw9714_id_table[] = {
> > +       {DW9714_NAME, 0},
> > +       {}
> > +};
> > +
> > +MODULE_DEVICE_TABLE(i2c, dw9714_id_table);
> > +
> > +static const struct dev_pm_ops dw9714_pm_ops = {
> > +       .suspend = dw9714_suspend,
> > +       .resume = dw9714_resume,
> > +       .runtime_suspend = dw9714_runtime_suspend,
> > +       .runtime_resume = dw9714_runtime_resume,
> 
> You can (and probably should) use SET_SYSTEM_SLEEP_PM_OPS() for global
> suspend/resume handlers and SET_RUNTIME_PM_OPS() for runtime ones.
> This also takes care of functions being undefined if !CONFIG_PM.
> 

Ack

> > +};
> > +
> > +static struct i2c_driver dw9714_i2c_driver = {
> > +       .driver = {
> > +               .name = DW9714_NAME,
> > +               .pm = &dw9714_pm_ops,
> > +#ifdef CONFIG_ACPI
> > +               .acpi_match_table = ACPI_PTR(dw9714_acpi_match),
> > +#endif
> 
> No need for #ifdef CONFIG_ACPI, as .acpi_match_table is always present in the
> struct and ACPI_PTR() takes care of dw9714_acpi_match being undefined if
> !CONFIG_ACPI.
> 

Ack

> Best regards,
> Tomasz