Re: [PATCH v2 1/1] i2c: omap: correct usage of the interrupt enableregister

[Oleksandr Dmytryshyn]

On 05/30/2013 07:46 PM, Kevin Hilman wrote:
> Oleksandr Dmytryshyn <oleksandr.dmytryshyn@xxxxxx> writes:
>
> > If the i2c controller during suspend will generate an interrupt, it
> > can lead to unpredictable behaviour in the kernel.
> >
> > Based on the logic of the kernel code interrupts from i2c should be
> > prohibited during suspend. Kernel writes 0 to the I2C_IE register in
> > the omap_i2c_runtime_suspend() function. In the other side kernel
> > writes saved interrupt flags to the I2C_IE register in
> > omap_i2c_runtime_resume() function. I.e. interrupts should be disabled
> > during suspend.
> >
> > This works for chips with version1 registers scheme. Interrupts are
> > disabled during suspend. For chips with version2 scheme registers
> > writting 0 to the I2C_IE register does nothing (because now the
> > I2C_IRQENABLE_SET register is located at this address). This register
> > is used to enable interrupts. For disabling interrupts
> > I2C_IRQENABLE_CLR register should be used.
> >
> > Because the registers I2C_IRQENABLE_SET and I2C_IE have the same
> > addresses, the interrupt enabling procedure is unchanged.
> >
> > Signed-off-by: Oleksandr Dmytryshyn <oleksandr.dmytryshyn@xxxxxx>
> Much better, but still doesn't explain how/why this has been working up
> until now.  Have we just been lucky?
Yes, this has been working up until now because we've just been lucky.
> > ---
> >   drivers/i2c/busses/i2c-omap.c | 15 +++++++++++----
> >   1 file changed, 11 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
> > index e02f9e3..2419899 100644
> > --- a/drivers/i2c/busses/i2c-omap.c
> > +++ b/drivers/i2c/busses/i2c-omap.c
> > @@ -180,6 +180,8 @@ enum {
> >   #define I2C_OMAP_ERRATA_I207		(1 << 0)
> >   #define I2C_OMAP_ERRATA_I462		(1 << 1)
> >   
> > +#define OMAP_I2C_INTERRUPTS_MASK	0x6FFF
> To be more clear, this should probably have v2 in the name.
I'll rename this mask in the patch-set v3
> Kevin


--

Best regards,
Oleksandr Dmytryshyn | OMAP4 Platform
GlobalLogic Inc. | Innovation by Design
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