linux-kernel - Re: [PATCH v3 4/6] spi: spi-axi-spi-engine: Add support for MOSI idle configuration

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Date: Fri, 7 Jun 2024 11:40:23 -0300
From: Marcelo Schmitt <marcelo.schmitt1@...il.com>
To: Nuno Sá <noname.nuno@...il.com>
Cc: David Lechner <dlechner@...libre.com>,
	Marcelo Schmitt <marcelo.schmitt@...log.com>, broonie@...nel.org,
	lars@...afoo.de, Michael.Hennerich@...log.com, jic23@...nel.org,
	robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
	conor+dt@...nel.org, nuno.sa@...log.com, linux-iio@...r.kernel.org,
	devicetree@...r.kernel.org, linux-spi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/6] spi: spi-axi-spi-engine: Add support for MOSI
 idle configuration

On 06/07, Nuno Sá wrote:
> On Thu, 2024-06-06 at 18:31 -0300, Marcelo Schmitt wrote:
> 
> ...
> 
> > 
> > 
> > 
> > When is a driver version check needed?
> > Yes, older versions of SPI-Engine won't support this, but the patch set should
> > cause no regression. Even if loading the current ad4000 driver with
> > older SPI-Engine HDL and driver, the ADC driver would get a warn (or error?)
> > and do what's possible without MOSI idle feature (probably only be able to do
> > reg access) or fail probing.
> > 
> 
> Maybe I'm missing something but with the patchset we unconditionally set
> SPI_MOSI_IDLE_HIGH. So if we load an hdl which does not support it things will
> apparently be ok but it won't actually work, right? If I'm right we should have
Yes, that's correct.

> a bit in a RO config_register telling us that the feature is being supported or
> not. That way we only set the mode bit if we do support it...

Ok, understood. Will do it for v4.

Thanks,
Marcelo

> 
> - Nuno Sá
> 
>