| Message ID | 20200427155037.218390-3-hdegoede@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,1/8] iio: light: cm32181: Add some extra register defines | expand |
Hi All, On 4/27/20 5:50 PM, Hans de Goede 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. > > From the ACPI/x86 side devices with more then 1 I2cSerialBus ACPI-resource > are handled by the drivers/platform/x86/i2c-multi-instantiate.c code. > This code will instantiate "cm32181" i2c_client-s for both resources. > > Add a check to cm32181_probe() for the client's address being the ARA > address, and in that case fail the probe with -ENODEV. > > On these ACPI systems the sensor may have a SMBus Alert asserted at boot, > if this is the case the sensor will not respond to any i2c_transfers on > its actual address until we read from the ARA register to clear the Alert. > > Therefor we must (try to) read a byte from the client with the ARA > register, before returning -ENODEV, so that we clear the Alert and when > we get called again for the client instantiated for the second > I2cSerialBus ACPI-resource the sensor will respond to our i2c-transfers. > > Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> > Signed-off-by: Hans de Goede <hdegoede@redhat.com> So this assumes that i2c-multi-inst will be used for ACPI CPLM3218 device nodes and we get 2 separate i2c_clients for the ARA, resp. the real address. This has been discussed on the linux-acpi list and the conclusion is that that instanting 2 full i2c_clients is not the right solution. Instead the cm32181 driver should create a "dummy" client for the second address (which is part of the same chip) itself, using an acpi version of i2c_new_dummy_device() or i2c_new_ancillary_device() I will prepare a v3 of this series with a better solution. Regards, Hans > --- > Changes in v2 > - s/i2c_client-s/I2C clients/ in added comment > --- > drivers/iio/light/cm32181.c | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > diff --git a/drivers/iio/light/cm32181.c b/drivers/iio/light/cm32181.c > index fd371b36c7b3..4c26a4a8a070 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, > }; > @@ -333,6 +335,20 @@ static int cm32181_probe(struct i2c_client *client, > struct iio_dev *indio_dev; > int ret; > > + /* > + * Some ACPI systems list 2 I2C resources for the CM3218 sensor, the > + * SMBus Alert Response Address (ARA, 0x0c) and the actual I2C address. > + * drivers/platform/x86/i2c-multi-instantiate.c instantiates "cm32181" > + * I2C clients for both resources, ignore the ARA client. > + * On these systems the sensor may have a SMBus Alert asserted at boot, > + * in that case the ARA must be read to clear the Alert otherwise the > + * sensor will not respond on its actual I2C address. > + */ > + if (client->addr == SMBUS_ALERT_RESPONSE_ADDRESS) { > + i2c_smbus_read_byte(client); > + return -ENODEV; > + } > + > indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*cm32181)); > if (!indio_dev) { > dev_err(&client->dev, "devm_iio_device_alloc failed\n"); >
diff --git a/drivers/iio/light/cm32181.c b/drivers/iio/light/cm32181.c index fd371b36c7b3..4c26a4a8a070 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, }; @@ -333,6 +335,20 @@ static int cm32181_probe(struct i2c_client *client, struct iio_dev *indio_dev; int ret; + /* + * Some ACPI systems list 2 I2C resources for the CM3218 sensor, the + * SMBus Alert Response Address (ARA, 0x0c) and the actual I2C address. + * drivers/platform/x86/i2c-multi-instantiate.c instantiates "cm32181" + * I2C clients for both resources, ignore the ARA client. + * On these systems the sensor may have a SMBus Alert asserted at boot, + * in that case the ARA must be read to clear the Alert otherwise the + * sensor will not respond on its actual I2C address. + */ + if (client->addr == SMBUS_ALERT_RESPONSE_ADDRESS) { + i2c_smbus_read_byte(client); + return -ENODEV; + } + indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*cm32181)); if (!indio_dev) { dev_err(&client->dev, "devm_iio_device_alloc failed\n");