linux-kernel - Re: [PATCH] mfd: cpcap: Fix interrupt regression with regmap clear

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Date:   Sun, 15 Nov 2020 18:31:30 +0100
From:   Pavel Machek <pavel@....cz>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Lee Jones <lee.jones@...aro.org>, linux-kernel@...r.kernel.org,
        Carl Philipp Klemm <philipp@...s.xyz>,
        Laxminath Kasam <lkasam@...eaurora.org>,
        Merlijn Wajer <merlijn@...zup.org>,
        Mark Brown <broonie@...nel.org>,
        Sebastian Reichel <sre@...nel.org>,
        Tim Harvey <tharvey@...eworks.com>
Subject: Re: [PATCH] mfd: cpcap: Fix interrupt regression with regmap
 clear_ack

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@...eworks.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@....cz>

Thank you, culomb counter issue is now gone.

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

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