Re: [PATCH] mfd: cpcap: Fix interrupt regression with regmap clear_ack

Pavel Machek
2020-11-15T17:32:35Z

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Hi!

> With commit 3a6f0fb7b8eb ("regmap: irq: Add support to clear ack
> registers"), the cpcap interrupts are no longer getting acked properly
> leading to a very unresponsive device with CPUs fully loaded spinning
> in the threaded IRQ handlers.
>
> To me it looks like the clear_ack commit above actually fixed a long
> standing bug in regmap_irq_thread() where we unconditionally acked the
> interrupts earlier without considering ack_invert. And the issue with
> cpcap started happening as we now also consider ack_invert.
>
> Tim Harvey <tharvey@gateworks.com> tried to fix this issue earlier with
> "[PATCH v2] regmap: irq: fix ack-invert", but the reading of the ack
> register was considered unnecessary for just ack_invert, and we did not
> have clear_ack available yet. As the cpcap irqs worked both with and
> without ack_invert earlier because of the unconditional ack, the
> problem remained hidden until now.
>
> Also, looks like the earlier v3.0.8 based Motorola Android Linux kernel
> does clear_ack style read-clear-write with "ireg_val & ~mreg_val" instead
> of just ack_invert style write. So let's switch cpcap to use clear_ack
> to fix the issue.
>
> Fixes: 3a6f0fb7b8eb ("regmap: irq: Add support to clear ack registers")

Tested-by: Pavel Machek <pavel@ucw.cz>

Thank you, culomb counter issue is now gone.

Best regards,
Pavel
--
http://www.livejournal.com/~pavelmachek

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