Re: [PATCH v3 06/11] iio: light: cm32181: Handle CM3218 ACPI devices with 2 I2C resources

[Hans de Goede <hdegoede@xxxxxxxxxx>]

Hi,

On 5/3/20 1:04 PM, Jonathan Cameron wrote:
> On Tue, 28 Apr 2020 19:29:18 +0200
> Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
>
> > Some ACPI systems list 2 I2C resources for the CM3218 sensor. On these
> > systems the first I2cSerialBus ACPI-resource points to the SMBus Alert
> > Response Address (ARA, 0x0c) and the second I2cSerialBus ACPI-resource
> > points to the actual CM3218 sensor address:
> >
> >   Method (_CRS, 0, NotSerialized)  // _CRS: Current Resource Settings
> >   {
> >       Name (SBUF, ResourceTemplate ()
> >       {
>
> I have a vague recollection that we had case of this where they could
> come in either order.  Could that happen here?

Not to the best of my knowledge. I've only seen this
construct on a couple of Asus models and they are all consistent.

> My mind may be playing tricks on me of course and that may never
> happen...
>
> Did I ever mention how much the lack of spec for some of these corner
> cases annoys me?

Yes I think you have mentioned before. Unfortunately there
is nothing we can do about this, but I hear you.

Regards,

Hans


> J
>
> >           I2cSerialBusV2 (0x000C, ControllerInitiated, 0x00061A80,
> >               AddressingMode7Bit, "\\_SB.I2C3",
> >               0x00, ResourceConsumer, , Exclusive,
> >               )
> >           I2cSerialBusV2 (0x0048, ControllerInitiated, 0x00061A80,
> >               AddressingMode7Bit, "\\_SB.I2C3",
> >               0x00, ResourceConsumer, , Exclusive,
> >               )
> >           Interrupt (ResourceConsumer, Level, ActiveHigh, Exclusive, ,, )
> >           {
> >               0x00000033,
> >           }
> >       })
> >       Return (SBUF) /* \_SB_.I2C3.ALSD._CRS.SBUF */
> >   }
> >
> > Detect this and take the following step to deal with it:
> >
> > 1. When a SMBus Alert capable sensor has an Alert asserted, it will
> >     not respond on its actual I2C address. Read a byte from the ARA
> >     to clear any pending Alerts.
> >
> > 2. Create a "dummy" client for the actual I2C address and
> >     use that client to communicate with the sensor.
> >
> > Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> > ---
> > Changes in v3:
> > - Create and use a dummy client instead of relying on i2c-multi-instantiate
> >    to create 2 separate clients for the 2 I2C resources
> >
> > Changes in v2
> > - s/i2c_client-s/I2C clients/ in added comment
> > ---
> >   drivers/iio/light/cm32181.c | 22 ++++++++++++++++++++++
> >   1 file changed, 22 insertions(+)
> >
> > diff --git a/drivers/iio/light/cm32181.c b/drivers/iio/light/cm32181.c
> > index 8fe49610fc26..c23a5c3a86a3 100644
> > --- a/drivers/iio/light/cm32181.c
> > +++ b/drivers/iio/light/cm32181.c
> > @@ -51,6 +51,8 @@
> >   #define CM32181_CALIBSCALE_RESOLUTION	1000
> >   #define MLUX_PER_LUX			1000
> >   
> > +#define SMBUS_ALERT_RESPONSE_ADDRESS	0x0c
> > +
> >   static const u8 cm32181_reg[CM32181_CONF_REG_NUM] = {
> >   	CM32181_REG_ADDR_CMD,
> >   };
> > @@ -335,6 +337,26 @@ static int cm32181_probe(struct i2c_client *client)
> >   	if (!indio_dev)
> >   		return -ENOMEM;
> >   
> > +	/*
> > +	 * Some ACPI systems list 2 I2C resources for the CM3218 sensor, the
> > +	 * SMBus Alert Response Address (ARA, 0x0c) and the actual I2C address.
> > +	 * Detect this and take the following step to deal with it:
> > +	 * 1. When a SMBus Alert capable sensor has an Alert asserted, it will
> > +	 *    not respond on its actual I2C address. Read a byte from the ARA
> > +	 *    to clear any pending Alerts.
> > +	 * 2. Create a "dummy" client for the actual I2C address and
> > +	 *    use that client to communicate with the sensor.
> > +	 */
> > +	if (ACPI_HANDLE(dev) && client->addr == SMBUS_ALERT_RESPONSE_ADDRESS) {
> > +		struct i2c_board_info board_info = { .type = "dummy" };
> > +
> > +		i2c_smbus_read_byte(client);
> > +
> > +		client = i2c_acpi_new_device(dev, 1, &board_info);
> > +		if (IS_ERR(client))
> > +			return PTR_ERR(client);
> > +	}
> > +
> >   	cm32181 = iio_priv(indio_dev);
> >   	cm32181->client = client;
> >