RE: [PATCH v2 2/3] gpio: Add support for TPS68470 GPIOs
From: Mani, Rajmohan
Date: Wed Jul 05 2017 - 21:49:46 EST
Hi Andy and all,
Thanks for your patience.
> > Main points (some I already told in an answer to Sakari's mail):
> > 1. Consider 2 GPIO chips over 1.
> I am looking into this.
For the second GPIO chip, the call to acpi_attach_data() fails with AE_ALREADY_EXISTS, as below with 4.12 rc3 kernel.
acpi_ns_attach_data() fails with AE_ALREADY_EXISTS for the second GPIO chip.
/* We only allow one attachment per handler */ drivers/acpi/acpica/nsobject.c
Also, I tried the following experiment, since we know the number of GPIOs for the second GPIO chip is 3, just to see if I can get further along after a successful call to acpi_attach_data().
Since the acpi_gpio_chip_dh is used as the handler in all acpi_gpiochip_* calls, I tried to use another handler (acpi_gpio_chip_dh2). But now, as expected, acpi_gpiochip_request_regions() failed inside acpi_gpiochip_add(), as only one OpRegion handler can be installed for a given OpRegion code. Due to this, when I try to set the GPIO 9 (which is now GPIO 2 of the second GPIO chip of 2 GPIO chips implementation), the OpRegion handler is called with the information / region_context pointer of the first GPIO chip, which is not desired.
It sounds like there are 2 issues with the 2 GPIO chips implementation.
1) How to get acpi_ns_attach_data() done successfully for the second GPIO chip, given the observation above and
2) How to get the GPIO OpRegion handler to be called with the right GPIO chip information / region_context pointer
I need pointers to make further progress here.
> > 2. Fix FIXME(s).
> Leaving this on, until I see how this can be fixed.
These FIXME code will be removed from the driver, as we are working to get this done through platform firmware.
> > 3. If there is hardware bug we should work around it must be clarified.
> If this is about initializing the GPIOs with zero, I have removed this code for
> > 4. You missed Linus' comments here (switch to the data pointer inside
> > GPIO chip and remove platform driver data stuff from the driver).
> I have fixed this with v3