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 ?
> On our platform, we never merged commit fcf690b0 and hence our DTS already
> defines the RESET pin as GPIO_ACTIVE_LOW. So, I don't have any issues at all
> with your patch! :-)
So in the end, the patch should be about a mere revert. I will update
accordingly when relevant, but before that I'll wait for some feedback about the
potential issue of this patch (forcing users to udpate faulty devicetree)
Thanks,
Alexis
--
Alexis Lothoré, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
