Re: [PATCH v2 1/2] pinctrl: meson: meson8b: fix requesting GPIOs greater than GPIOZ_3

[Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>]

Hi Linus,

On Fri, Mar 2, 2018 at 10:48 AM, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> On Sun, Feb 25, 2018 at 12:38 PM, Martin Blumenstingl
> <martin.blumenstingl@xxxxxxxxxxxxxx> wrote:
>
>> Meson8b is a cost reduced variant of the Meson8 SoC. It's package size
>> is smaller than Meson8.
>> Unfortunately there are a few key differences which cannot be seen
>> without close inspection of the code and the public S805 datasheet:
>> - the GPIOX bank is missing the GPIOX_12, GPIOX_13, GPIOX_14 and
>>   GPIOX_15 GPIOs
>> - the GPIOY bank is missing the GPIOY_2, GPIOY_4, GPIOY_5, GPIOY_15 and
>>   GPIOY_16 GPIOs
>> - the GPIODV bank is missing all GPIOs except GPIODV_9, GPIODV_24,
>>   GPIODV_25, GPIODV_26, GPIODV_27, GPIODV_28 and GPIODV_29
>> - the GPIOZ bank is missing completely
>> - there is a new GPIO bank called "DIF"
>>
>> This means that Meson8b only has 83 actual GPIO lines. Without any holes
>> there would be 130 GPIO lines in total (120 are inherited from Meson8
>> plus 10 new from the DIF bank).
>>
>> GPIOs greater GPIOZ_3 (whose ID is 83 - as a reminder: this is exactly
>> the number of actual GPIO lines on Meson8b and also the value of
>> meson8b_cbus_pinctrl_data.num_pins) cannot berequested. Using CARD_6
>> (which used ID 100 prior to this patch, "base of the GPIO controller was
>> 382) as an example:
>> $ echo 482 > /sys/class/gpio/export
>> export_store: invalid GPIO 482
>>
>> This removes all non-existing pins from to dt-bindings header file
>> (include/dt-bindings/gpio/meson8b-gpio.h). This allows us to have a
>> consecutive numbering for the GPIO #defines (GPIOY_2 doesn't exist for
>> example, so previously the GPIOY_3 ID was "GPIOY_1 + 2", after this
>> patch it is "GPIOY_1 + 1"). As a nice side-effect this means that we get
>> compile-time (instead of runtime) errors if Meson8b .dts uses a pin that
>> only exists on Meson8.
>>
>> Additionally the pinctrl-meson8b driver has to be updated to handle this
>> new GPIO numbering. By default a struct meson_bank only handles GPIO
>> banks where the pins are numbered consecutively because it calculates
>> the bit offsets based on the GPIO IDs.
>> This is solved by  taking the original BANK() definition and splitting it
>> into consecutive subsets (X0..11 and X16..21). The bit offsets for each
>> new bank includes the skipped GPIOs (the definition of the "X0..11" bank
>> is identical to the old "X" bank apart from the "last IRQ" field, the
>> definition of the new, split "X16..21" bank takes the original "X" bank
>> and adds 16 - the start of the new split bank - to the "first IRQ",
>> pullen bit, pull bit, dir bit, out bit and in bit).
>>
>> Commit 984cffdeaeb7ea ("pinctrl: Fix gpio/pin mapping for Meson8b")
>> fixed the same issue by setting "ngpio" (of the gpio_chip) to 130.
>> Unfortunately this broke in db80f0e158e621 ("pinctrl: meson: get rid of
>> unneeded domain structures").
>> The solution from this patch was considered to be better than the
>> previous attempt at fixing this because it provides compile-time error
>> checking for the GPIOs that exist on Meson8 but don't exist on Meson8b.
>>
>> The following pins were tested on an Odroid-C1 using the sysfs GPIO
>> interface checking that their value (high or low) could be read:
>> - GPIOX_0, GPIOX_1, GPIOX_2, GPIOX_3, GPIOX_4, GPIOX_5, GPIOX_6,
>>   GPIOX_7, GPIOX_8, GPIOX_9, GPIOX_10, GPIOX_11, GPIOX_18, GPIOX_19,
>>   GPIOX_20, GPIOX_21
>> - GPIOY_3, GPIOY_7, GPIOY_8
>> (some of these had to be pulled up because they were low by default,
>> others were high by default so these had to be pulled down)
>>
>> Reported-by: Linus Lüssing <linus.luessing@xxxxxxxxx>
>> Suggested-by: Jerome Brunet <jbrunet@xxxxxxxxxxxx>
>> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
>
> Patch applied with Jerome's review tag.
thank you!

> Do I need to queue this for v4.16 fixes or is v4.17 good
> enough?
>
> Should it even be tagged for stable?
in my opinion v4.17 is good

the CARD, BOOT and DIF banks are affected (and only when trying to use
them as GPIO, pinctrl still works without this patch).
as far as I can see only CARD_6 (SD card detection) and BOOT_9 (eMMC
reset) are used as GPIOs on Odroid-C1 (I assume that other boards only
use these too)

this issue only came up when adding SD card support for Odroid-C1
it went unnoticed for ~1.5 years, so I believe it won't hurt anybody
if it "only" makes it into v4.17


Regards
Martin
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