On 14/10/21 10:21 pm, Linus Walleij wrote:
On Thu, Oct 14, 2021 at 1:05 PM Shreeya Patel
<shreeya.patel@xxxxxxxxxxxxx> wrote:
We are racing the registering of .to_irq when probing the
i2c driver. This results in random failure of touchscreen
devices.
Following errors could be seen in dmesg logs when gc->to_irq is NULL
[2.101857] i2c_hid i2c-FTS3528:00: HID over i2c has not been provided an Int IRQ
[2.101953] i2c_hid: probe of i2c-FTS3528:00 failed with error -22
To avoid this situation, defer probing until to_irq is registered.
This issue has been reported many times in past and people have been
using workarounds like changing the pinctrl_amd to built-in instead
of loading it as a module or by adding a softdep for pinctrl_amd into
the config file.
References :-
https://bugzilla.kernel.org/show_bug.cgi?id=209413
https://github.com/Syniurge/i2c-amd-mp2/issues/3
Signed-off-by: Shreeya Patel <shreeya.patel@xxxxxxxxxxxxx>
I understand the issue.
There is one problem.
@@ -3084,7 +3084,7 @@ int gpiod_to_irq(const struct gpio_desc *desc)
return retirq;
}
- return -ENXIO;
+ return -EPROBE_DEFER;
If you after five minutes plug in a USB FTDI or similar UART thing
with a GPIO expander, and someone request an IRQ from
one of those lines (they do not support interrupts), why should
it return -EPROBE_DEFER?
The point is that I think this will in certain circumstances return
a bogus error.
I was worried about the same but didn't really know under what scenario
this could occur.
Thanks for pointing this out.
We cannot merge this other than with a fat comment above:
/*
* This is semantically WRONG because the -EPROBE_DEFER
* is really just applicable during system bring-up.
*/
return -EPROBE_DEFER;
Can we use some kind of late_initcall() to just switch this over
to -ENXIO after a while?
I have sent a v2 which tries to fix this in an easy way. Let me know
what do you
think about that approach or else we could also think about using
late_initcall().
Thanks,
Shreeya Patel
Yours,
Linus Walleij
