Re: [PATCH RFC] wifi: wilc1000: fix reset line assert/deassert polarity

[Kalle Valo]

(Adding devicetree list for comments)

<Ajay.Kathat@xxxxxxxxxxxxx> writes:

> On 2/13/24 09:58, Alexis Lothoré wrote:
>> 
>> On 2/13/24 17:42, David Mosberger-Tang wrote:
>>> On Tue, 2024-02-13 at 16:22 +0100, Alexis Lothoré wrote:
>>>> When using a wilc1000 chip over a spi bus, users can optionally define a
>>>> reset gpio and a chip enable gpio. The reset line of wilc1000 is active
>>>> low, so to hold the chip in reset, a low (physical) value must be applied.
>>>>
>>>> The corresponding device tree binding documentation was introduced by
>>>> commit f31ee3c0a555 ("wilc1000: Document enable-gpios and reset-gpios
>>>> properties") and correctly indicates that the reset line is an active-low
>>>> signal. However, the corresponding driver part, brought by commit
>>>> ec031ac4792c ("wilc1000: Add reset/enable GPIO support to SPI driver"), is
>>>> misusing the gpiod APIs and apply an inverted logic when powering up/down
>>>> the chip (for example, setting the reset line to a logic "1" during power
>>>> up, which in fact asserts the reset line when device tree describes the
>>>> reset line as GPIO_ACTIVE_LOW).
>>>
>>> Note that commit ec031ac4792c is doing the right thing in regards to an
>>> ACTIVE_LOW RESET pin and the binding documentation is consistent with that code.
>>>
>>> It was later on that commit fcf690b0 flipped the RESET line polarity to treat it
>>> as GPIO_ACTIVE_HIGH.  I never understood why that was done and, as you noted, it
>>> introduced in inconsistency with the binding documentation.
>> 
>> Ah, you are right, and I was wrong citing your GPIOs patch as faulty
>> (git-blaming too fast !), thanks for the clarification. I missed this patch from
>> Ajay (fcf690b0) flipping the reset logic. Maybe he had issues while missing
>> proper device tree configuration and then submitted this flip ?
>
> Indeed, it was done to align the code as per the DT entry suggested in
> WILC1000/3000 porting guide[1 -page 18], which is already used by most
> of the existing users. This change has impact on the users who are using
> DT entry from porting guide. One approach is to retain the current code
> and document this if needed.

So if I'm understanding the situation correctly Microchip's porting
guide[1] doesn't match with kernel.org documentation[2]? I'm not the
expert here but from my point of view the issue is clear: the code needs
to follow kernel.org documentation[2], not external documentation.

I'll add devicetree list so hopefully people there can comment also,
full patch available in [3].

Alexis, if there are no more comments I'm in favor submitting the revert
you mentioned.


[1] https://ww1.microchip.com/downloads/en/DeviceDoc/ATWILC1000-ATWILC3000-ATWILC-Devices-Linux-Porting-Guide-User-Guide-DS70005329C.pdf

[2] Documentation/devicetree/bindings/net/wireless/microchip,wilc1000.yaml

[3] https://patchwork.kernel.org/project/linux-wireless/patch/20240213-wilc_1000_reset_line-v1-1-e01da2b23fed@xxxxxxxxxxx/

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