[U-Boot] [PATCH] pinctrl: renesas: Fix linker error when PINCTRL_PFC=n

[Marek Vasut]

On 4/3/19 2:30 PM, Dirk Behme wrote:
> On 03.04.2019 14:11, Marek Vasut wrote:
>> On 4/2/19 7:02 PM, Eugeniu Rosca wrote:
>>> On Tue, Apr 02, 2019 at 06:02:46PM +0200, Marek Vasut wrote:
>>>> On 4/2/19 5:40 PM, Eugeniu Rosca wrote:
>>>>> On Tue, Apr 02, 2019 at 05:28:43PM +0200, Marek Vasut wrote:
>>>>>> On 4/2/19 5:17 PM, Dirk Behme wrote:
>>>>>>> On 02.04.19 15:34, Marek Vasut wrote:
>>>>>>>> On 4/2/19 3:18 PM, Eugeniu Rosca wrote:
>>>>>>>>> With CONFIG_PINCTRL_PFC=n, aarch64-linux-gnu-ld reports:
>>>>>>>>>
>>>>>>>>> -----8<-----
>>>>>>>>>     LD      u-boot
>>>>>>>>> drivers/gpio/built-in.o: In function `rcar_gpio_request':
>>>>>>>>> drivers/gpio/gpio-rcar.c:128: undefined reference to
>>>>>>>>> `sh_pfc_config_mux_for_gpio'
>>>>>>>>> -----8<-----
>>> [..]
>>>>>>>> Does CONFIG_PINCTRL_PFC=n produce a bootable binary ?
>>>>>>>
>>>>>>> Why not? Main memory, boot device and UART are configured before
>>>>>>> U-Boot,
>>>>>>> no?
>>>>>>
>>>>>> It depends on what is running before U-Boot, so not necessarily.
>>>>>>
>>>>>> And speaking of boot device, consider the case where the system runs
>>>>>> from eMMC and uses the HS200/HS400 modes, which need to switch bus
>>>>>> mode
>>>>>> using the pinmux driver.
>>>>>>
>>>>>> Is there a real-world use case where you would want to disable the
>>>>>> pinmux driver ? And what is the benefit of that, except that it would
>>>>>> cause all kinds of weird problems.
>>>>>
>>>>> My H3ULCB-KF boots just fine [1] with CONFIG_PINCTRL_PFC=n, but I
>>>>> personally don't have any use-case which I need to fulfill on a
>>>>> Renesas reference design by disabling PFC.
>>>>
>>>> And the eMMC and SDHI both work fine too in HS400/SDR104 modes ?
>>>> They cannot, since you cannot switch the pinmux properties of the bus.
>>>> What about the errors in the log below, they don't look quite fine.
>>>>
>>>>> Rather, the motivation here is to ensure U-Boot builds fine with as
>>>>> many randconfig results as possible, which is a standard practice in
>>>>> Linux. I personally favor my solution, but I am also open minded if
>>>>> the linker error is avoided by introducing a direct/reverse dependency
>>>>> between PFC and another relevant R-Car3 Kconfig symbol.
>>>>
>>>> I am fine with fixing randconfig build errors. My question here is
>>>> whether it makes sense to allow U-Boot build without PFC support,
>>>> since that would cause all kinds of problems. I am banking toward
>>>> playing it safe and not allowing such an option at all. Thoughts ?
>>>
>>> It looks like in Linux, PINCTRL is a fundamental feature selected
>>> (i.e. *cannot* be disabled by users) by ARCH_RENESAS since v4.5 commit
>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=26a7e06dfee9
>>>
>>> ("arm64: renesas: r8a7795: Add Renesas R8A7795 SoC support").
>>>
>>> So, demanding a PFC-free U-Boot doesn't look reasonable to me.
>>
>> That's sensible.
>>
>>> Should PINCTRL be selected by CONFIG_RCAR_GEN3 as it is done in Linux?
>>> One caveat is that PINCTRL currently depends on DM, so R-Car3 U-Boot
>>> would become dependent on DM too, i.e. users won't have the option of
>>> a legacy U-Boot anymore.
>>
>> Non-DM operation is not supported anyway, the direction is toward DM/DT
>> support. Ultimately, it should be possible to have a single U-Boot
>> binary and just exchange the DT to support different boards.
>>
>> My concern is with the size of the PFC tables, they are massive, sparse
>> and keep growing, but that's a different topic.
>>
>> That said, what about making the GPIO driver depend on PFC driver and
>> then have Gen3 select PFC by default in Kconfig ?
> 
> 
> Of course, you can add such a dependency in Kconfig. But that's not the
> question here and won't fix the issue:

What is the question then ?

> It won't fix the issue that we have code encapsulated with a CONFIG_*
> option and a caller which is not encapsulated with this.
> 
> To fix this with your proposal, you need to merge CONFIG_PINCTRL_PFC and
> CONFIG_RCAR_GPIO to *one* CONFIG_RCAR_PINCTRL_PFC_GPIO (or whatever) to
> ensure that both, the function definition *and* the caller are
> encapsulated by the *same* CONFIG switch. But this sounds somehow quite
> strange to me ...

I don't think I understand this part. If the GPIO driver depends on the
PFC driver in Kconfig, then you can either have
- both compiled in
- neither PFC nor GPIO driver
- only the PFC driver
and all three options provide working result. Did I miss something ?

We can add this patch too, but I'd like to see the Kconfig fix alongside
it. Note that the patch should use #if CONFIG_IS_ENABLED(PINCTRL_PFC) .

-- 
Best regards,
Marek Vasut