On Sat, Feb 24, 2018 at 11:43:03PM +0100, Tobias Jordan wrote:
> pm_runtime_get_sync() increases the device's usage count even when
> reporting an error, so add a call to pm_runtime_put_noidle() in the
> error branch.
the increment is unconditional:
pm_runtime_get_sync
-> __pm_runtime_resume(dev, RPM_GET_PUT);
-> if (rpmflags & RPM_GET_PUT) atomic_inc(&dev->power.usage_count);
the decrement though is conditional:
pm_runtime_put_noidle
-> atomic_add_unless(&dev->power.usage_count, -1, 0);
would it not be possible to use an atomic_dec() here rahter than
atomic_add_unless() ? probably only a few cylces
Also just wondering - could one not decrement in pm_runtime_get_sync on the
error path rather than defering this to the caller and fixing it there ?
something like:
int __pm_runtime_resume(struct device *dev, int rpmflags)
{
...
if (rpmflags & RPM_GET_PUT)
atomic_inc(&dev->power.usage_count);
spin_lock_irqsave(&dev->power.lock, flags);
retval = rpm_resume(dev, rpmflags);
spin_unlock_irqrestore(&dev->power.lock, flags);
if (retival < 0)
atomic_dec(&dev->power.usage_count);
return retval;
}
that would require other changes then I guess (did not look into it).
but if resume fails does it ever make sense to increment the use count ?
>
> Fixes: 93222bd9b966 ("i2c: img-scb: Add runtime PM")
> Signed-off-by: Tobias Jordan <Tobias.Jordan@xxxxxxxxxxxxxx>
Reviewed-by: Nicholas Mc Guire <der.herr@xxxxxxx>
> ---
> This is one of a number of patches for problems found using coccinelle
> scripting in the SIL2LinuxMP project. The patch has been compile-tested;
> it's based on linux-next-20180223.
>
> For a discussion of the corresponding issue, see
> https://marc.info/?l=linux-pm&m=151904483924999&w=2
>
> drivers/i2c/busses/i2c-img-scb.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-img-scb.c b/drivers/i2c/busses/i2c-img-scb.c
> index f038858b6c54..569a1a8a2753 100644
> --- a/drivers/i2c/busses/i2c-img-scb.c
> +++ b/drivers/i2c/busses/i2c-img-scb.c
> @@ -1061,8 +1061,10 @@ static int img_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> }
>
> ret = pm_runtime_get_sync(adap->dev.parent);
> - if (ret < 0)
> + if (ret < 0) {
> + pm_runtime_put_noidle(adap->dev.parent);
> return ret;
> + }
>
> for (i = 0; i < num; i++) {
> struct i2c_msg *msg = &msgs[i];
> @@ -1162,8 +1164,10 @@ static int img_i2c_init(struct img_i2c *i2c)
> int ret;
>
> ret = pm_runtime_get_sync(i2c->adap.dev.parent);
> - if (ret < 0)
> + if (ret < 0) {
> + pm_runtime_put_noidle(i2c->adap.dev.parent);
> return ret;
> + }
>
> rev = img_i2c_readl(i2c, SCB_CORE_REV_REG);
> if ((rev & 0x00ffffff) < 0x00020200) {
> --
> 2.11.0
>
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