Re: [PATCH] spi: tegra114: initialize native chip selects inactive

On 28/07/2026 21:03, Abraham Zukor wrote:
> On 28/07/2026 10:34, Jon Hunter wrote:
>> Exactly. That's my point. Which is the right one? The answer is
>> probably neither, but whatever is present on the bus.
> 
> I think that defaulting to active-low is correct. The Tegra234 SPI
> controller hardware defaults to active-low (all bits in CS_POL_INACTIVE
> are set) so an active-high device is already asserted before this driver
> initializes. I checked the controller drivers under drivers/spi/; they
> either default to active-low or preserve the hardware default.

I am a bit reluctant to make this change after 10+ years of this driver 
being around.

> A more complex option is to scan the device tree children, check each
> item for whether it uses native chip select (as opposed to GPIO CS) and
> check for spi-cs-high. I found no other spi drivers that do this at
> probe time, and I don't think it's worth the complexity, but I can send
> it as a v2 if needed.

Right. Although this patch is specific to Tegra, I am guessing that 
other devices could also face similar issues and therefore, it would 
seem that having a generic facility to scan the devices would be ideal.

Jon

-- 
nvpublic