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

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Message-ID: <04b1296ff98a0accbf962a4a4bafc2e85a9869ae.camel@gmail.com>
Date: Fri, 07 Jun 2024 09:15:54 +0200
From: Nuno Sá <noname.nuno@...il.com>
To: Marcelo Schmitt <marcelo.schmitt1@...il.com>, David Lechner
	 <dlechner@...libre.com>
Cc: 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 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
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...

- Nuno Sá