Hi All,
Sorry, for the late reply.
+ CC Huzefa Kankroliwala - who is I2C driver owner on Android Kernel 3.4.
Regarding this patch - from my point of view, it fixes corner case and not an issue in general.
Let take a look on resume sequence:
- platform resume
- syscore resume
- resume_noirq
- enable IRQs - resume_device_irqs()
|- at this point IRQ handler will be invoked if IRQ state is IRQS_PENDING.
|- so, the I2C device IRQ handler may be called at time when I2C adapter IRQ is still disabled and, as result, the I2C device IRQ-handler may fail. (I2C device and I2C adapter may use different physical IRQ lines)
- resume_late
|- enable I2C bus IRQ
Possibly, the better way is to enable/disable I2C bus IRQ when needed - in our case in omap_i2c_xfer().
We use such approach in Android kernel 3.4
(http://git.omapzoom.org/?p=kernel/omap.git;a=commitdiff;h=1445a4d3b587c164bd30d108b61760aaaa07365e)
Grygorii
________________________________________
From: Kevin Hilman [khilman@xxxxxxxxxxxxxxxxxxx]
Sent: Friday, October 12, 2012 12:08 AM
To: Kalle Jokiniemi
Cc: linux-i2c@xxxxxxxxxxxxxxx; w.sang@xxxxxxxxxxxxxx; ben-linux@xxxxxxxxx; tony@xxxxxxxxxxx; linux-omap@xxxxxxxxxxxxxxx; Strashko, Grygorii; Datta, Shubhrajyoti
Subject: Re: [PATCH v3] ARM: OMAP: i2c: fix interrupt flood during resume
Hi Kalle,
Kalle Jokiniemi <kalle.jokiniemi@xxxxxxxxxxxxxxx> writes:
> The resume_noirq enables interrupts one-by-one starting from
> first one. Now if the wake up event for suspend came from i2c
> device, the i2c bus irq gets enabled before the threaded
> i2c device irq, causing a flood of i2c bus interrupts as the
> threaded irq that should clear the event is not enabled yet.
>
> Fixed the issue by adding suspend_noirq and resume_early
> functions that keep i2c bus interrupts disabled until
> resume_noirq has run completely.
>
> Issue was detected doing a wake up from autosleep with
> twl4030 power key on N9. Patch tested on N9.
>
> Signed-off-by: Kalle Jokiniemi <kalle.jokiniemi@xxxxxxxxxxxxxxx>
This version looks good, thanks for the extra comments.
Reviewed-by: Kevin Hilman <khilman@xxxxxx>
Tested-by: Kevin Hilman <khilman@xxxxxx>
Wolfram, This should also probably be Cc'd to stable since it affects
earlier kernels as well. Thanks,
Kevin
> ---
> drivers/i2c/busses/i2c-omap.c | 34 ++++++++++++++++++++++++++++++++++
> 1 files changed, 34 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
> index a0e49f6..991341b 100644
> --- a/drivers/i2c/busses/i2c-omap.c
> +++ b/drivers/i2c/busses/i2c-omap.c
> @@ -1132,6 +1132,36 @@ static int __devexit omap_i2c_remove(struct platform_device *pdev)
> }
>
> #ifdef CONFIG_PM
> +#ifdef CONFIG_PM_SLEEP
> +static int omap_i2c_suspend_noirq(struct device *dev)
> +{
> +
> + struct platform_device *pdev = to_platform_device(dev);
> + struct omap_i2c_dev *_dev = platform_get_drvdata(pdev);
> +
> + /* Disabling irq here to balance the enable in resume_early */
> + disable_irq(_dev->irq);
> + return 0;
> +}
> +
> +static int omap_i2c_resume_early(struct device *dev)
> +{
> +
> + struct platform_device *pdev = to_platform_device(dev);
> + struct omap_i2c_dev *_dev = platform_get_drvdata(pdev);
> +
> + /*
> + * The noirq_resume enables the interrupts one by one,
> + * this causes a interrupt flood if the SW irq actually reading
> + * event from i2c device is enabled only after i2c bus irq, as the
> + * irq that should clear the event is still disabled. We have to
> + * keep the bus irq disabled until all other irqs have been enabled.
> + */
> + enable_irq(_dev->irq);
> +
> + return 0;
> +}
> +#endif
> #ifdef CONFIG_PM_RUNTIME
> static int omap_i2c_runtime_suspend(struct device *dev)
> {
> @@ -1183,6 +1213,10 @@ static int omap_i2c_runtime_resume(struct device *dev)
> #endif /* CONFIG_PM_RUNTIME */
>
> static struct dev_pm_ops omap_i2c_pm_ops = {
> +#ifdef CONFIG_PM_SLEEP
> + .suspend_noirq = omap_i2c_suspend_noirq,
> + .resume_early = omap_i2c_resume_early,
> +#endif
> SET_RUNTIME_PM_OPS(omap_i2c_runtime_suspend,
> omap_i2c_runtime_resume, NULL)
> };
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