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

Hans de Goede
2020-04-28T17:29:57Z

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 ()
{
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@redhat.com>
---
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;

--
2.26.0