Re: [PATCH 2/5] i2c: omap: add runtime check in isr to be sure thati2c is enabled

[Grygorii Strashko]

Hi Felipe,
On 06/07/2013 10:02 PM, Felipe Balbi wrote:
> Hi,
>
> On Fri, Jun 07, 2013 at 09:46:05PM +0300, Grygorii Strashko wrote:
> > Add runtime check at the beginning of omap_i2c_isr/omap_i2c_isr_thread
> > to be sure that i2c is enabled, before performing IRQ handling and accessing
> > I2C IP registers:
> > 	if (pm_runtime_suspended(dev->dev)) {
> > 		WARN_ONCE(true, "We should never be here!\n");
> > 		return IRQ_NONE;
> > 	}
> >
> > Produce warning in case if ISR called when i2c is disabled
> >
> > CC: Kevin Hilman <khilman@xxxxxxxxxx>
> > Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx>
> > ---
> >   drivers/i2c/busses/i2c-omap.c |   10 ++++++++++
> >   1 file changed, 10 insertions(+)
> >
> > diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
> > index 97844ff..2dac598 100644
> > --- a/drivers/i2c/busses/i2c-omap.c
> > +++ b/drivers/i2c/busses/i2c-omap.c
> > @@ -885,6 +885,11 @@ omap_i2c_isr(int irq, void *dev_id)
> >   	u16 stat;
> >   
> >   	spin_lock(&dev->lock);
> > +	if (pm_runtime_suspended(dev->dev)) {
> > +		WARN_ONCE(true, "We should never be here!\n");
> > +		return IRQ_NONE;
> > +	}
> returning IRQ_NONE is not what you want to do in this case. You want to
> setup a flag so that your runtime_resume() knows that there are pending
> events to be handled and you handle those in runtime_resume time.
I don't want to handle this IRQ - we should never be here.
Will be changed to  IRQ_HANDLED.
> But to be frank, I don't see how this can trigger since we're calling
> pm_runtime_get_sync() from omap_i2c_xfer() which means by the time
> pm_runtime_get_sync() returns, assuming no errors, i2c module should be
> fully resumed and ready to go. Perhaps you have found a bug somewhere
> else ?
May be it's better to revert this patch:
e3a36b207f76364c281aeecaf14c1b22a7247278
i2c: omap: remove unnecessary pm_runtime_suspended check

which doesn't cover case when transfer is *finished*.
Please, see https://patchwork.kernel.org/patch/2689211/ and
cover-latter.
> Also, your 'We should never be here' message isn't helpfull at all.
>
> > @@ -905,6 +910,11 @@ omap_i2c_isr_thread(int this_irq, void *dev_id)
> >   	u16 stat;
> >   	int err = 0, count = 0;
> >   
> > +	if (pm_runtime_suspended(dev->dev)) {
> > +		WARN_ONCE(true, "We should never be here!\n");
> > +		return IRQ_NONE;
> > +	}
> because of IRQF_ONESHOT I can't see how this would *ever* be a valid
> check.
Please, see https://patchwork.kernel.org/patch/2689211/ and
cover-latter.

Sorry, for delayed reply - I've had problems with my e-mail.

- grygorii
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