linux-kernel - Re: [RESEND PATCH] rtc: ds1343: Force SPI chip select to be active high

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Message-ID: <6f122282-1675-497f-bc2f-0bbfba6640aa@mev.co.uk>
Date: Thu, 11 Jul 2024 16:29:07 +0100
From: Ian Abbott <abbotti@....co.uk>
To: Mark Brown <broonie@...nel.org>
Cc: Alexandre Belloni <alexandre.belloni@...tlin.com>,
 linux-rtc@...r.kernel.org, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org, Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [RESEND PATCH] rtc: ds1343: Force SPI chip select to be active
 high

On 11/07/2024 15:21, Mark Brown wrote:
> On Thu, Jul 11, 2024 at 03:05:01PM +0100, Ian Abbott wrote:
> 
>> I think the devicetree node for the RTC device ought to be setting
>> `spi-cs-high` but cannot do so at the moment because the driver clobbers it.
> 
> Specifying spi-cs-high in the device tree should almost always be
> redundant or a mistake, if the device needs a high chip select then we
> already know that from the compatible.  The property is adding nothing
> but potential confusion, in the normal course of affairs the driver
> should just specify the configuration it needs for the bus.

So `spi->mode |= SPI_CS_HIGH;` is safer than `spi->mode ^= SPI_CS_HIGH;`?

Regarding `spi-cs-high` in the device tree, what about the compatibility 
table for `spi-cs-high` and `cs-gpio` active level in 
"Documentation/devicetree/bindings/spi/spi-controller.yaml"?

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