On Fri, Nov 13, 2020 at 2:21 AM Lee Jones <lee.jo...@linaro.org> wrote:
>
> On Wed, 11 Nov 2020, Tony Lindgren wrote:
>
> > 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 <thar...@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")
> > Cc: Carl Philipp Klemm <phil...@uvos.xyz>
> > Cc: Laxminath Kasam <lka...@codeaurora.org>
> > Cc: Merlijn Wajer <merl...@wizzup.org>
> > Cc: Mark Brown <broo...@kernel.org>
> > Cc: Pavel Machek <pa...@ucw.cz>
> > Cc: Sebastian Reichel <s...@kernel.org>
> > Cc: Tim Harvey <thar...@gateworks.com>
>
> It would be nice to have you review this Tim.
>
Tony / Lee,
Thanks for keeping me in the loop on this. I still haven't properly
resolved the issue with my device/driver interrupts
(drivers/mfd/gateworks_gsc.c) which requires ack_invert (writing 0 to
clearing interrupt bits).
3a6f0fb7b8eb ("regmap: irq: Add support to clear ack registers")
appears to not only add the new clear_ack case it also attempts to
resolve the long standing ack_invert issue with this change:
- ret = regmap_write(map, reg, data->status_buf[i]);
+ if (chip->ack_invert)
+ ret = regmap_write(map, reg,
+ ~data->status_buf[i]);
+ else
+ ret = regmap_write(map, reg,
+ data->status_buf[i]);
However, this still doesn't resolve the issue I have with my
device/driver because it ends up writing 1's to all the other bits in
the ack register which keeps my device's interrupt from de-asserting.
Perhaps that's a strange behavior of my device that it allows you to
'set' interrupt source bits which causes the interrupt to stay
asserted? I'm also wondering if my issue is that I currently have the
interrupt registered as such:
ret = devm_regmap_add_irq_chip(dev, gsc->regmap, client->irq,
IRQF_ONESHOT | IRQF_SHARED | IRQF_TRIGGER_FALLING, 0, &gsc_irq_chip,
&irq_data);
Perhaps this should be IRQF_TRIGGER_LOW as the device will not
de-assert its IRQ# until all source bits are cleared.
Tony, I thought that your pcap issue was that it truly did not have an
inverted ack and the fact that ack_invert did not work was why you
never noticed any issue. If this is true I would think you would want
to disable ack_invert but not necessarily enable clear_ack. Did your
testing show it needed to toggle the ack to clear it?
Best Regards,
Tim
