From: Shawn Guo <shawnguo@kernel.org>
To: Fabio Estevam <festevam@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org, linus.walleij@linaro.org,
linux-imx@nxp.com, kernel@pengutronix.de
Subject: Re: [PATCH] ARM: dts: imx: Fix the SPI chipselect polarity
Date: Sun, 30 Aug 2020 09:38:31 +0800 [thread overview]
Message-ID: <20200830013819.GA32096@dragon> (raw)
In-Reply-To: <20200819210424.8844-1-festevam@gmail.com>
On Wed, Aug 19, 2020 at 06:04:24PM -0300, Fabio Estevam wrote:
> The conversion of the spi-imx driver to use GPIO descriptors
> in commit 8cdcd8aeee28 ("spi: imx/fsl-lpspi: Convert to GPIO descriptors")
> helped to detect the following SPI chipselect polarity mismatch on an
> imx6q-sabresd:
>
> [ 4.854337] m25p80@0 enforce active low on chipselect handle
>
> Prior to the above commit, the chipselect polarity passed via cs-gpios
> property was ignored and considered active-low.
>
> The reason for such mismatch is clearly explained in the comments inside
> drivers/gpio/gpiolib-of.c:
>
> * SPI children have active low chip selects
> * by default. This can be specified negatively
> * by just omitting "spi-cs-high" in the
> * device node, or actively by tagging on
> * GPIO_ACTIVE_LOW as flag in the device
> * tree. If the line is simultaneously
> * tagged as active low in the device tree
> * and has the "spi-cs-high" set, we get a
> * conflict and the "spi-cs-high" flag will
> * take precedence.
>
> To properly represent the SPI chipselect polarity, change it to active-low
> when the "spi-cs-high" property is absent.
>
> Signed-off-by: Fabio Estevam <festevam@gmail.com>
Applied, thanks.
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prev parent reply other threads:[~2020-08-30 1:40 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-19 21:04 [PATCH] ARM: dts: imx: Fix the SPI chipselect polarity Fabio Estevam
2020-08-28 9:25 ` Linus Walleij
2020-08-30 1:38 ` Shawn Guo [this message]
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