Hi Tomas,

On Fri, May 12, 2023 at 06:55:08PM +0200, Tomáš Mudruňka wrote:

quoted

So this is still racy, isn't it? The interrupt may come after read is
done, but before we register the handler.

Well. It is. But please see the rest of the thread, where we've
already discussed this.

Every time the interrupt handler runs, the interrupt is disabled and
then reenabled after i2c communication is done. Which means this exact
thing happens on each keypress anyway. So i don't think it's a
necessarily huge deal. It might not be perfect solution, but it makes
things much better. window in which the deadlock condition can happen
is now in range of few ms (or us), instead of ~10 seconds (previously
it included bootloader and basicaly any moment from power up to driver
load)

Right, but the point is that there are some alternatives to reduce the
range to zero. You posted one already, but I mistakenly advised against
it due to my own oversight :)

Another solution would be to trigger on LOW instead of FALLING as
proposed in initial version of the patch. That would be safer in terms
of lm8333 deadlock, but Jeff was concerned about possibility of
interrupt storm taking down whole system in case the IRQ line gets
stuck in LOW for some reason...

Just to clarify, this is not my concern; all bets are off in case of
gross hardware failure such as this. Rather, my recommendations are:

1. Level (or edge) sensitivity should be specified in dts, not hard-coded
in the driver.

2. If you open support for level-triggered interrupts, you should verify
on a scope whether there is any chance that the IRQ line may still be in
the process of rising at the moment the read is completed. The datasheet
is ambiguous here.

Tom

pá 12. 5. 2023 v 1:44 odesílatel Dmitry Torokhov
[off-list ref] napsal:

quoted

On Wed, May 03, 2023 at 08:44:06PM -0500, Jeff LaBundy wrote:

quoted

Hi Tomas,

On Wed, May 03, 2023 at 05:32:31PM +0200, Tomas Mudrunka wrote:

quoted

LM8333 uses gpio interrupt line which is triggered by falling edge.
When button is pressed before driver is loaded,
driver will miss the edge and never respond again.
To fix this we run the interrupt handler before registering IRQ
to clear the interrupt via i2c command.

Signed-off-by: Tomas Mudrunka <redacted>
---

Reviewed-by: Jeff LaBundy <redacted>

quoted

 drivers/input/keyboard/lm8333.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/input/keyboard/lm8333.c b/drivers/input/keyboard/lm8333.c
index 7457c3220..52108c370 100644
--- a/drivers/input/keyboard/lm8333.c
+++ b/drivers/input/keyboard/lm8333.c

@@ -178,6 +178,8 @@ static int lm8333_probe(struct i2c_client *client)
                    dev_warn(&client->dev, "Unable to set active time\n");
    }

+   lm8333_irq_thread(client->irq, lm8333);

So this is still racy, isn't it? The interrupt may come after read is
done, but before we register the handler.

quoted

quoted

+
    err = request_threaded_irq(client->irq, NULL, lm8333_irq_thread,
                               IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
                               "lm8333", lm8333);
--
2.40.1

Thanks.

--
Dmitry

Kind regards,
Jeff LaBundy