Re: [PATCH v5] mfd: cros_ec_dev: Register cros_ec_accel_legacy driver as a subdevice

[Gwendal Grignou]

On Mon, Apr 1, 2019 at 8:46 PM Lee Jones <lee.jones@xxxxxxxxxx> wrote:
>
> On Wed, 27 Feb 2019, Gwendal Grignou wrote:
>
> > From: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx>
> >
> > With this patch, the cros_ec_ctl driver will register the legacy
> > accelerometer driver (named cros_ec_accel_legacy) if it fails to
> > register sensors through the usual path cros_ec_sensors_register().
> > This legacy device is present on Chromebook devices with older EC
> > firmware only supporting deprecated EC commands (Glimmer based devices).
> >
> > Tested-by: Gwendal Grignou <gwendal@xxxxxxxxxxxx>
> > Signed-off-by: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx>
> > Reviewed-by: Gwendal Grignou <gwendal@xxxxxxxxxxxx>
> > Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
> > ---
> > Changes in v5:
> > - Remove unnecessary white lines.
> >
> > Changes in v4:
> > - [5/8] Nit: EC -> ECs (Lee Jones)
> > - [5/8] Statically define cros_ec_accel_legacy_cells (Lee Jones)
> >
> > Changes in v3:
> > - [5/8] Add the Reviewed-by Andy Shevchenko.
> >
> > Changes in v2:
> > - [5/8] Add the Reviewed-by Gwendal.
> >
> >  drivers/mfd/cros_ec_dev.c | 66 +++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 66 insertions(+)
> >
> > diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
> > index d275deaecb12..64567bd0a081 100644
> > --- a/drivers/mfd/cros_ec_dev.c
> > +++ b/drivers/mfd/cros_ec_dev.c
> > @@ -376,6 +376,69 @@ static void cros_ec_sensors_register(struct cros_ec_dev *ec)
> >       kfree(msg);
> >  }
> >
> > +static struct cros_ec_sensor_platform sensor_platforms[] = {
> > +     { .sensor_num = 0 },
> > +     { .sensor_num = 1 }
> > +};
>
> I'm still very uncomfortable with this struct.
>
> Other than these indices, the sensors have no other distinguishing
> features, thus there should be no need to identify or distinguish
> between them in this way.
When initializing the sensors, the IIO driver expect to find in the
data  structure pointed by dev_get_platdata(dev), in field sensor_num
is stored the index assigned by the embedded controller to talk to a
given sensor.
cros_ec_sensors_register() use the same mechanism; in that function,
the sensor_num field is populated from the output of an EC command
MOTIONSENSE_CMD_INFO. In case of legacy mode, that command may not be
available and in any case we know the EC has only either 2
accelerometers present or nothing.

For instance, let's compare a legacy device with a more recent one:

legacy:
type                  |   id          | sensor_num   | device name
accelerometer  |   0           |   0                  | cros-ec-accel.0
accelerometer  |   1           |   1                  | cros-ec-accel.1

Modern:
type                  |   id          | sensor_num   | device name
accelerometer  |   0           |   0                  | cros-ec-accel.0
accelerometer  |   1           |   1                  | cros-ec-accel.1
gyroscope        |    0          |    2                 | cros-ec-gyro.0
magnetometer |    0          |   3                  | cros-ec-mag.0
light                  |    0          |   4                  | cros-ec-light.0
...

Gwendal.

>
> > +static const struct mfd_cell cros_ec_accel_legacy_cells[] = {
> > +     {
> > +             .name = "cros-ec-accel-legacy",
> > +             .id = 0,
> > +             .platform_data = &sensor_platforms[0],
> > +             .pdata_size = sizeof(struct cros_ec_sensor_platform),
> > +     },
> > +     {
> > +             .name = "cros-ec-accel-legacy",
> > +             .id = 1,
> > +             .platform_data = &sensor_platforms[1],
> > +             .pdata_size = sizeof(struct cros_ec_sensor_platform),
> > +     }
> > +};
> > +
> > +static void cros_ec_accel_legacy_register(struct cros_ec_dev *ec)
> > +{
> > +     struct cros_ec_device *ec_dev = ec->ec_dev;
> > +     u8 status;
> > +     int ret;
> > +
> > +     /*
> > +      * ECs that need legacy support are the main EC, directly connected to
> > +      * the AP.
> > +      */
> > +     if (ec->cmd_offset != 0)
> > +             return;
> > +
> > +     /*
> > +      * Check if EC supports direct memory reads and if EC has
> > +      * accelerometers.
> > +      */
> > +     if (!ec_dev->cmd_readmem)
> > +             return;
> > +
> > +     ret = ec_dev->cmd_readmem(ec_dev, EC_MEMMAP_ACC_STATUS, 1, &status);
> > +     if (ret < 0) {
> > +             dev_warn(ec->dev, "EC does not support direct reads.\n");
> > +             return;
> > +     }
> > +
> > +     /* Check if EC has accelerometers. */
> > +     if (!(status & EC_MEMMAP_ACC_STATUS_PRESENCE_BIT)) {
> > +             dev_info(ec->dev, "EC does not have accelerometers.\n");
> > +             return;
> > +     }
> > +
> > +     /*
> > +      * Register 2 accelerometers
> > +      */
> > +     ret = mfd_add_devices(ec->dev, PLATFORM_DEVID_AUTO,
>
> Using PLATFORM_DEVID_AUTO whilst providing the MFD cells with IDs
> doesn't make any sense.  Please remove the IDs from the cells.
Removed in V6.
>
> > +                           cros_ec_accel_legacy_cells,
> > +                           ARRAY_SIZE(cros_ec_accel_legacy_cells),
> > +                           NULL, 0, NULL);
> > +     if (ret)
> > +             dev_err(ec_dev->dev, "failed to add EC sensors\n");
> > +}
> > +
> >  static const struct mfd_cell cros_ec_cec_cells[] = {
> >       { .name = "cros-ec-cec" }
> >  };
> > @@ -437,6 +500,9 @@ static int ec_device_probe(struct platform_device *pdev)
> >       /* check whether this EC is a sensor hub. */
> >       if (cros_ec_check_features(ec, EC_FEATURE_MOTION_SENSE))
> >               cros_ec_sensors_register(ec);
> > +     else
> > +             /* Workaroud for older EC firmware */
> > +             cros_ec_accel_legacy_register(ec);
> >
> >       /* Check whether this EC instance has CEC host command support */
> >       if (cros_ec_check_features(ec, EC_FEATURE_CEC)) {
>
> --
> Lee Jones [æçæ]
> Linaro Services Technical Lead
> Linaro.org â Open source software for ARM SoCs
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