From: Hans de Goede <hdegoede@redhat.com>
To: "Rafael J . Wysocki" <rjw@rjwysocki.net>,
Len Brown <lenb@kernel.org>, Darren Hart <dvhart@infradead.org>,
Andy Shevchenko <andy@infradead.org>,
Jonathan Cameron <jic23@kernel.org>
Cc: linux-acpi@vger.kernel.org, platform-driver-x86@vger.kernel.org,
linux-kernel@vger.kernel.org, Hartmut Knaack <knaack.h@gmx.de>,
Lars-Peter Clausen <lars@metafoo.de>,
Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
linux-iio@vger.kernel.org,
Andy Shevchenko <andy.shevchenko@gmail.com>
Subject: Re: [PATCH v2 3/8] iio: light: cm32181: Handle ACPI instantiating a cm32181 client on the SMBus ARA
Date: Mon, 27 Apr 2020 20:31:15 +0200 [thread overview]
Message-ID: <2dae8c05-c84c-3caf-f84a-34615183ab01@redhat.com> (raw)
In-Reply-To: <20200427155037.218390-3-hdegoede@redhat.com>
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");
>
next prev parent reply other threads:[~2020-04-27 18:31 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-27 15:50 [PATCH v2 1/8] iio: light: cm32181: Add some extra register defines Hans de Goede
2020-04-27 15:50 ` [PATCH v2 2/8] iio: light: cm32181: Add support for the CM3218 Hans de Goede
2020-04-27 15:50 ` [PATCH v2 3/8] iio: light: cm32181: Handle ACPI instantiating a cm32181 client on the SMBus ARA Hans de Goede
2020-04-27 18:31 ` Hans de Goede [this message]
2020-04-27 15:50 ` [PATCH v2 4/8] iio: light: cm32181: Change reg_init to use a bitmap of which registers to init Hans de Goede
2020-04-27 15:50 ` [PATCH v2 5/8] iio: light: cm32181: Use units of 1/100000th for calibscale and lux_per_bit Hans de Goede
2020-04-27 15:50 ` [PATCH v2 6/8] iio: light: cm32181: Make lux_per_bit and lux_per_bit_base_it runtime settings Hans de Goede
2020-04-27 15:50 ` [PATCH v2 7/8] iio: light: cm32181: Add support for parsing CPM0 and CPM1 ACPI tables Hans de Goede
2020-04-27 15:50 ` [PATCH v2 8/8] iio: light: cm32181: Fix integartion time typo Hans de Goede
2020-04-27 18:29 ` [PATCH v2 1/8] iio: light: cm32181: Add some extra register defines Hans de Goede
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