Re: [PATCH] gpiolib: acpi: support override broken GPIO number in ACPI table

[Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>]

On Thu, Mar 04, 2021 at 08:32:14PM +0100, Hans de Goede wrote:
> Hi,
> 
> On 3/3/21 10:47 AM, Andy Shevchenko wrote:
> > On Fri, Feb 26, 2021 at 11:39:19AM +0800, Shawn Guo wrote:
> >> Running kernel with ACPI on Lenovo Flex 5G laptop, touchpad is just
> >> not working.  That's because the GpioInt number of TSC2 node in ACPI
> >> table is simply wrong, and the number even exceeds the maximum GPIO
> >> lines.  As the touchpad works fine with Windows on the same machine,
> >> presumably this is something Windows-ism.  Although it's obviously
> >> a specification violation, believe of that Microsoft will fix this in
> >> the near future is not really realistic.
> >>
> >> It adds the support of overriding broken GPIO number in ACPI table
> >> on particular machines, which are matched using DMI info.  Such
> >> mechanism for fixing up broken firmware and ACPI table is not uncommon
> >> in kernel.  And hopefully it can be useful for other machines that get
> >> broken GPIO number coded in ACPI table.
> > 
> > 
> > +Cc: Hans.
> > 
> > Hans, would appreciate your opinion on this thread. Maybe I'm mistaken in my
> > conclusions.
> 
> So I've read the entire thread here:
> https://lore.kernel.org/linux-gpio/20210226033919.8871-1-shawn.guo@xxxxxxxxxx/T/#u
> 
> And I agree wih Andy, this is not something which should be fixed up in the
> generic gpiolib-acpi code.
> 
> Note that we have similar things going on on x86 platforms. There are cases
> there where there are e.g. holes in the GPIO ranges advertised by the Intel
> pinctrl drivers. And in the beginning as i2c (and thus GpioIRQ) HID devices
> started to become more common there were also several rounds of work to make
> sure that the GPIO numbering (per ACPI-device / island) exported to the rest
> of the kernel (and thus to gpiolib-acpi) matched with the numbering which
> the ACPI tables expected (so the numbering which the Windows driver use).
> 
> It seems to me, esp. in the light that there are a lot of "crazy high" GPIO
> indexes in the DSDT of the Lenovo Flex 5G, that the right thing to do here
> is to fix the qualcom pinctrl/GPIO driver to number its GPIOs in the way
> expected by these ACPI tables. This will break use of existing devicetrees,
> so it will likely need to detect if the main firmware of the system is ACPI
> or DT based and then use 2 different numbering schemes depending on the
> outcome of that check.
> 
> Please also do not try ti fix this with some quirks in e.g. the i2c-hid driver,
> I will definitely NACK such attempts. From what we can see now any fix clearly
> should be done inside the qualcom GPIO driver.

Hans, thank you very much!

-- 
With Best Regards,
Andy Shevchenko