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

Andy Shevchenko
2021-03-04T00:13:29Z

On Tue, Mar 02, 2021 at 10:02:49PM -0700, Jeffrey Hugo wrote:
> On 3/2/2021 5:21 AM, Andy Shevchenko wrote:
> > On Tue, Mar 02, 2021 at 08:27:26AM +0800, Shawn Guo wrote:
> > > On Mon, Mar 01, 2021 at 02:17:06PM +0200, Andy Shevchenko wrote:
> > > > On Sat, Feb 27, 2021 at 11:19:45AM +0800, Shawn Guo wrote:
> > > > > On Fri, Feb 26, 2021 at 01:19:21PM +0200, Andy Shevchenko wrote:
> > > > > > On Fri, Feb 26, 2021 at 12:57:37PM +0200, Andy Shevchenko wrote:
> > > > > > > On Fri, Feb 26, 2021 at 11:39 AM Shawn Guo <shawn.guo@linaro.org> wrote:
> > > > > > > > On Fri, Feb 26, 2021 at 11:12:07AM +0200, Andy Shevchenko wrote:
> > > > > > > > > On Fri, Feb 26, 2021 at 5:42 AM Shawn Guo <shawn.guo@linaro.org> 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.
> > > > > > > > >
> > > > > > > > > Thanks for the report and patch.
> > > > > > > > >
> > > > > > > > > First of all, have you reported the issue to Lenovo? At least they
> > > > > > > > > will know that they did wrong.
> > > > > > > >
> > > > > > > > Yes, we are reporting this to Lenovo, but to be honest, we are not sure
> > > > > > > > how much they will care about it, as they are shipping the laptop with
> > > > > > > > Windows only.
> > > > > > > >
> > > > > > > > > Second, is it possible to have somewhere output of `acpidump -o
> > > > > > > > > flex5g.dat` (the flex5g.dat file)?
> > > > > > > >
> > > > > > > > https://raw.githubusercontent.com/aarch64-laptops/build/master/misc/lenovo-flex-5g/dsdt.dsl
> > > > > >
> > > > > > Looking into DSDT I think the problem is much worse. First of all there are
> > > > > > many cases where pins like 0x140, 0x1c0, etc are being used. On top of that
> > > > > > there is no GPIO driver in the upstream (as far as I can see by HID, perhaps
> > > > > > there is a driver but for different HID. And I see that GPIO device consumes a
> > > > > > lot of Interrupts from GIC as well (it's ARM platfrom as far as I understand).
> > > > >
> > > > > Yes, it's a laptop built on Qualcomm Snapdragon SC8180X SoC. The GPIO
> > > > > driver is generic for all Snapdragon SoCs, and has been available in
> > > > > upstream for many years (for DT though). It can be found as the gpio_chip
> > > > > implementation in MSM pinctrl driver [1]. The SC8180X specific part can
> > > > > be found as pinctrl-sc8180x.c [2], and it's already working for DT boot.
> > > > > The only missing piece is to add "QCOM040D" as the acpi_device_id to
> > > > > support ACPI boot, and it will be submitted after 5.12-rc1 comes out.
> > > > >
> > > > > > Looking at the Microsoft brain damaged way of understanding GPIOs and hardware
> > > > > > [1], I am afraid you really want to have a specific GPIO driver for this. So,
> > > > > > for now until we have better picture of what's going on, NAK to this patch.
> > > > >
> > > > > Thanks for the pointer to Microsoft document. On Snapdragon, we have
> > > > > only one GPIO instance that accommodates all GPIO pins, so I'm not sure
> > > > > that Microsoft GPIOs mapping layer is relevant here at all.
> > > > >
> > > > > Please take a look at the GPIO driver, and feel free to let me know if
> > > > > you need any further information to understand what's going on.
> > > >
> > > > Yes, I looked into the driver and see that it has 3 blocks of GPIOs (we call
> > > > them communities, but in the driver the term 'tiles' is used) AFAIU (correct me
> > > > if I'm wrong). And who knows how many banks in each of them.
> > >
> > > I'm not sure that the 3 'tiles' means 3 blocks of GPIOs. Maybe, @Bjorn
> > > can help clarify. But the ACPI table shows that there is only 'GIO0'
> > > with 'QCOM040D' HID.
> >
> > Yeah, I already got that ACPI there is screwed up...
> >
> > > > I'm afraid that MS does on his way and not yours.
> > > >
> > > > Can we have TRM for GPIO IP used there and any evidence / document from
> > > > firmware team about the implementation of the GPIO numbering in the ACPI
> > > > (at Intel we have so called BIOS Writers Guide that is given to the customers
> > > > where such info can be found)?
> > >
> > > Unfortunately, I do not have the access to any sort of these documents.
> > > But I looped in Jeffrey who is part of Qualcomm kernel/firmware team,
> > > and should be able to help clarify GPIO numbering in the ACPI table.
> >
> > Thanks! Will wait for new information then.
>
> Sorry, just joining the thread now. Hopefully I'm addressing everything
> targeted at me.
>
> I used to do kernel work on MSMs, then kernel work on server CPUs, but now I
> do kernel work on AI accelerators. Never was on the firmware team, but I
> have a lot of contacts in those areas. On my own time, I support Linux on
> the Qualcomm laptops.
>
> Its not MS that needs to fix things (although there is plenty of things I
> could point to that MS could fix), its the Qualcomm Windows FW folks. They
> have told me a while ago they were planning on fixing this issue on some
> future chipset, but apparently that hasn't happened yet. Sadly, once these
> laptops ship, they are in a frozen maintenance mode.

I see. MS indeed loves Linux then :-)

> In my opinion, MS has allowed Qualcomm to get away with doing bad things in
> ACPI on the Qualcomm laptops. The ACPI is not a true hardware description
> that is OS agnostic as it should be, and probably violates the spec in many
> ways. Instead, the ACPI is written against the Windows drivers, and has a
> lot of OS driver crap pushed into it.

You meant "ACPI" -> "DSDT on the certain platform" I hope.

> The GPIO description is one such thing.
>
> As I understand it, any particular SoC will have a number of GPIOs supported
> by the TLMM. 0 - N. Linux understands this. However, in the ACPI of the
> Qualcomm Windows laptops, you will likely find atleast one GPIO number which
> exceeds this N. These are "virtual" GPIOs, and are a construct of the
> Windows Qualcomm TLMM driver and how it interfaces with the frameworks
> within Windows.
>
> Some GPIO lines can be configured as wakeup sources by routing them to a
> specific hardware block in the SoC (which block it is varies from SoC to
> SoC). Windows has a specific weird way of handling this which requires a
> unique "GPIO chip" to handle. GPIO chips in Windows contain 32 GPIOs, so
> for each wakeup GPIO, the TLMM driver creates a GPIO chip (essentially
> creating 32 GPIOs), and assigns the added GPIOs numbers which exceed N. The
> TLMM driver has an internal mapping of which virtual GPIO number corresponds
> to which real GPIO.
>
> So, ACPI says that some peripheral has GPIO N+X, which is not a real GPIO.
> That peripheral goes and requests that GPIO, which gets routed to the TLMM
> driver, and the TLMM driver translates that number to the real GPIO, and
> provides the reference back to the peripheral, while also setting up the
> special wakeup hardware.
>
> So, N+1 is the first supported wakup GPIO, N+1+32 is the next one, then
> N+1+32+32, and so on.
>
> I see how this creates a nice mess for running Linux on these laptops, but I
> don't have a good idea how to work around it. Per SoC, you'd need to know
> the mapping and translate it for ACPI when running the Windows version of
> the FW (yes most Qualcomm MSMs have OS specific firmware), but reject such
> gpio numbers when running other firmware, or I guess on different targets.

Thank, this makes a lot of sense to me and (unfortunately) I'm familiar with
this concept on some of x86 cheap tablets.

Since the mapping of those wake IRQs is totally platform specific, it needs a
platform driver. On above mentioned x86 platforms we have a one you may take as
an example (good or bad it's another story):
drivers/platform/x86/intel_int0002_vgpio.c.

I think you will need something like this somewhere in ARM platform
infrastructure in the Linux kernel.

That said, I don't see that those numbers are "broken", they have their own
meaning and specific mapping to the real GPIOs and it's so platform specific,
that we can't treat it as a quirk.

Thanks, Jeffrey, it is helpful!

> > > > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pinctrl/qcom/pinctrl-msm.c#n713
> > > > > [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pinctrl/qcom/pinctrl-sc8180x.c

--
With Best Regards,
Andy Shevchenko