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

Hans de Goede
2020-05-04T09:52:55Z

Hi,

On 5/3/20 1:04 PM, Jonathan Cameron wrote:
> On Tue, 28 Apr 2020 19:29:18 +0200
> Hans de Goede <hdegoede@redhat.com> 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@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;
>>
>