Re: [PATCH v2 1/5] i2c: Don't start transfers when suspended

Bastian Hecht
2014-07-17T14:58:21Z

I want to add the remark that I can't help further on the patch series
in the next month about. So this is free to be taken/ignored/modified
without any approval by my side.

Have fun coding,

Bastian

2014-07-17 16:48 GMT+02:00 Bastian Hecht <hechtb@gmail.com>:
> 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.
>
> Several bus drivers handle this problem on their own. We can clean things up
> by moving the protection mechanism into the core.
>
> Signed-off-by: Bastian Hecht <hechtb@gmail.com>
> ---
> changelog v2:
>
> - commit message extended.
> - initialization added for adap->suspended
> - swapped branch for increased performance
>
>
> drivers/i2c/i2c-core.c | 25 ++++++++++++++++++++++++-
> include/linux/i2c.h | 1 +
> 2 files changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index 7c7f4b8..b15dc20 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);
> @@ -1243,6 +1257,7 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
> dev_set_name(&adap->dev, "i2c-%d", adap->nr);
> adap->dev.bus = &i2c_bus_type;
> adap->dev.type = &i2c_adapter_type;
> + adap->suspended = false;
> res = device_register(&adap->dev);
> if (res)
> goto out_list;
> @@ -1819,7 +1834,10 @@ 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 = __i2c_transfer(adap, msgs, num);
> + else
> + ret = -EIO;
> i2c_unlock_adapter(adap);
>
> return ret;
> @@ -2577,6 +2595,10 @@ 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 +2612,7 @@ 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
>