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Date: Tue, 01 Oct 2013 18:24:07 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc: linux-i2c@...r.kernel.org, Wolfram Sang <wsa@...-dreams.de>,
Aaron Lu <aaron.lu@...el.com>, Lv Zheng <lv.zheng@...el.com>,
Mark Brown <broonie@...nel.org>,
Kevin Hilman <khilman@...aro.org>,
Sylwester Nawrocki <s.nawrocki@...sung.com>,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-acpi@...r.kernel.org
Subject: Re: [PATCH v4] i2c: enable runtime PM for I2C adapter devices enumerated from ACPI
On Tuesday, October 01, 2013 04:09:42 PM Mika Westerberg wrote:
> The ACPI specification requires the parent device to be powered on before
> any of its children. It can be only powered off when all the children are
> already off.
>
> Currently whenever there is no I2C traffic going on, the I2C controller
> driver can put the device into low power state transparently to its
> children (the I2C client devices). This violates the ACPI specification
> because now the parent device is in lower power state than its children.
>
> In order to keep ACPI happy we enable runtime PM for the I2C adapter device
> if we find out that the I2C controller was in fact an ACPI device. In
> addition to that we attach the I2C client devices to the ACPI power domain
> and make sure that they are powered on when the driver ->probe() is called.
>
> Non-ACPI devices are not affected by this change.
>
> This patch is based on the work by Aaron Lu and Lv Zheng.
>
> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> Changes to v3:
> * Check only client ACPI_HANDLE().
> * Fixed bug where we attach the device to ACPI power domain multiple
> times.
> * Functions are renamed to _get_attach/_put_attach to make it clear that
> we do attach/detach as well.
>
> drivers/i2c/i2c-core.c | 47 ++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 46 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index 29d3f04..e289b1d 100644
> --- a/drivers/i2c/i2c-core.c
> +++ b/drivers/i2c/i2c-core.c
> @@ -236,6 +236,27 @@ int i2c_recover_bus(struct i2c_adapter *adap)
> return adap->bus_recovery_info->recover_bus(adap);
> }
>
> +static void acpi_i2c_device_pm_get_attach(struct i2c_client *client,
> + bool attach)
> +{
> + if (ACPI_HANDLE(&client->dev)) {
> + /* Make sure the adapter is active */
> + pm_runtime_get_sync(&client->adapter->dev);
> + if (attach)
> + acpi_dev_pm_attach(&client->dev, true);
> + }
> +}
> +
> +static void acpi_i2c_device_pm_put_detach(struct i2c_client *client,
> + bool detach)
> +{
> + if (ACPI_HANDLE(&client->dev)) {
> + if (detach)
> + acpi_dev_pm_detach(&client->dev, true);
> + pm_runtime_put(&client->adapter->dev);
> + }
> +}
> +
> static int i2c_device_probe(struct device *dev)
> {
> struct i2c_client *client = i2c_verify_client(dev);
> @@ -254,11 +275,15 @@ static int i2c_device_probe(struct device *dev)
> client->flags & I2C_CLIENT_WAKE);
> dev_dbg(dev, "probe\n");
>
> + acpi_i2c_device_pm_get_attach(client, true);
> +
> status = driver->probe(client, i2c_match_id(driver->id_table, client));
> if (status) {
> client->driver = NULL;
> i2c_set_clientdata(client, NULL);
> }
> +
> + acpi_i2c_device_pm_put_detach(client, !!status);
> return status;
> }
>
> @@ -271,6 +296,8 @@ static int i2c_device_remove(struct device *dev)
> if (!client || !dev->driver)
> return 0;
>
> + acpi_i2c_device_pm_get_attach(client, false);
> +
> driver = to_i2c_driver(dev->driver);
> if (driver->remove) {
> dev_dbg(dev, "remove\n");
> @@ -283,6 +310,8 @@ static int i2c_device_remove(struct device *dev)
> client->driver = NULL;
> i2c_set_clientdata(client, NULL);
> }
> +
> + acpi_i2c_device_pm_put_detach(client, true);
> return status;
> }
>
> @@ -294,8 +323,11 @@ static void i2c_device_shutdown(struct device *dev)
> if (!client || !dev->driver)
> return;
> driver = to_i2c_driver(dev->driver);
> - if (driver->shutdown)
> + if (driver->shutdown) {
> + acpi_i2c_device_pm_get_attach(client, false);
> driver->shutdown(client);
> + acpi_i2c_device_pm_put_detach(client, false);
> + }
> }
>
> #ifdef CONFIG_PM_SLEEP
> @@ -1263,6 +1295,16 @@ exit_recovery:
> bus_for_each_drv(&i2c_bus_type, NULL, adap, __process_new_adapter);
> mutex_unlock(&core_lock);
>
> + /*
> + * For ACPI enumerated controllers we must make sure that the
> + * controller is powered on before its children. Runtime PM handles
> + * this for us once we have enabled it for the adapter device.
> + */
> + if (ACPI_HANDLE(adap->dev.parent)) {
> + pm_runtime_no_callbacks(&adap->dev);
> + pm_runtime_enable(&adap->dev);
> + }
> +
> return 0;
>
> out_list:
> @@ -1427,6 +1469,9 @@ void i2c_del_adapter(struct i2c_adapter *adap)
> return;
> }
>
> + if (ACPI_HANDLE(adap->dev.parent))
> + pm_runtime_disable(&adap->dev);
> +
> /* Tell drivers about this removal */
> mutex_lock(&core_lock);
> bus_for_each_drv(&i2c_bus_type, NULL, adap,
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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