Hi Bastian,
On Sat, Jul 12, 2014 at 01:49:27PM +0200, Bastian Hecht wrote:
> i2c transfer requests come in very uncontrolled, like from interrupt routines.
> We might be suspended when this happens. To avoid i2c timeouts caused by
> powered down busses we check for suspension.
>
> Signed-off-by: Bastian Hecht <hechtb@xxxxxxxxx>
Thanks for doing this! I add linux-pm to CC because of two questions.
> ---
> I ended up getting i2c timeouts when suspending and provoking touchscreen
> IRQs on an Armadillo board with an sh_mobile i2c bus. Instead of copying
> again the protection mechanism from other bus drivers, we can clean things
> up and move this into the core.
This could be part of the commit message IMO.
>
> I assume that all bus drivers use kzalloc or equivalent for the
> struct i2c_adapter. So adap->suspended can't end up uninitialized,
> right?
Better safe than sorry, I'd say. Please add the initialization.
> We could consider using this scheme for freeze/restore too.
linux-pm: opinions?
>
>
> drivers/i2c/i2c-core.c | 24 +++++++++++++++++++++++-
> include/linux/i2c.h | 1 +
> 2 files changed, 24 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index 7c7f4b8..9fe9581 100644
> --- a/drivers/i2c/i2c-core.c
> +++ b/drivers/i2c/i2c-core.c
> @@ -343,6 +343,13 @@ static int i2c_legacy_resume(struct device *dev)
> static int i2c_device_pm_suspend(struct device *dev)
> {
> const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
> + struct i2c_adapter *adap = i2c_verify_adapter(dev);
> +
> + if (adap) {
> + i2c_lock_adapter(adap);
> + adap->suspended = true;
> + i2c_unlock_adapter(adap);
> + }
>
> if (pm)
> return pm_generic_suspend(dev);
> @@ -353,6 +360,13 @@ static int i2c_device_pm_suspend(struct device *dev)
> static int i2c_device_pm_resume(struct device *dev)
> {
> const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
> + struct i2c_adapter *adap = i2c_verify_adapter(dev);
> +
> + if (adap) {
> + i2c_lock_adapter(adap);
> + adap->suspended = false;
> + i2c_unlock_adapter(adap);
> + }
>
> if (pm)
> return pm_generic_resume(dev);
> @@ -1819,7 +1833,10 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
> i2c_lock_adapter(adap);
> }
>
> - ret = __i2c_transfer(adap, msgs, num);
> + if (adap->suspended)
> + ret = -EIO;
> + else
> + ret = __i2c_transfer(adap, msgs, num);
a) Minor: I'd swap the branches and invert the condition, so that the
more expected code path comes first
b) linux-pm: I wonder about the return code. Currently, some drivers
return -EIO, some -EBUSY. Do you care which? Since we try to have
designated fault codes in the i2c subsystem, I wonder about -ESHUTDOWN?
Or is this too much of hijacking fault codes?
> i2c_unlock_adapter(adap);
>
> return ret;
> @@ -2577,6 +2594,10 @@ s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags,
>
> if (adapter->algo->smbus_xfer) {
> i2c_lock_adapter(adapter);
> + if (adapter->suspended) {
> + res = -EIO;
> + goto unlock;
> + }
>
> /* Retry automatically on arbitration loss */
> orig_jiffies = jiffies;
> @@ -2590,6 +2611,7 @@ s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags,
> orig_jiffies + adapter->timeout))
> break;
> }
> +unlock:
> i2c_unlock_adapter(adapter);
>
> if (res != -EOPNOTSUPP || !adapter->algo->master_xfer)
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index b556e0a..af08c75 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -434,6 +434,7 @@ struct i2c_adapter {
> int timeout; /* in jiffies */
> int retries;
> struct device dev; /* the adapter device */
> + unsigned int suspended:1;
>
> int nr;
> char name[48];
> --
> 1.9.1
>
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