linux-kernel - Re: [PATCH 0/2] spi: amlogic: meson-spicc: Use pinctrl to drive CLK line when idle

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Message-ID: <09081275-be9c-9d0c-856b-ed2df8fc0b13@linaro.org>
Date:   Tue, 27 Sep 2022 10:30:06 +0200
From:   Neil Armstrong <neil.armstrong@...aro.org>
To:     Amjad Ouled-Ameur <aouledameur@...libre.com>, broonie@...nel.org
Cc:     linux-kernel@...r.kernel.org, linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-spi@...r.kernel.org,
        narmstrong@...libre.com
Subject: Re: [PATCH 0/2] spi: amlogic: meson-spicc: Use pinctrl to drive CLK
 line when idle

Hi Amjad,

On 09/08/2022 19:20, Amjad Ouled-Ameur wrote:
> Between SPI transactions, all SPI pins are in HiZ state. When using the SS
> signal from the SPICC controller it's not an issue because when the
> transaction resumes all pins come back to the right state at the same time
> as SS.
> 
> The problem is when we use CS as a GPIO. In fact, between the GPIO CS
> state change and SPI pins state change from idle, you can have a missing or
> spurious clock transition.
> 
> Set a bias on the clock depending on the clock polarity requested before CS
> goes active, by passing a special "idle-low" and "idle-high" pinctrl state
> and setting the right state at a start of a message.
> 
> Amjad Ouled-Ameur (2):
>    spi: dt-bindings: amlogic, meson-gx-spicc: Add pinctrl names for SPI
>      signal states
>    spi: meson-spicc: Use pinctrl to drive CLK line when idle
> 
>   .../bindings/spi/amlogic,meson-gx-spicc.yaml  | 15 +++++++
>   arch/arm64/boot/dts/amlogic/meson-gxl.dtsi    | 14 +++++++
>   drivers/spi/spi-meson-spicc.c                 | 39 ++++++++++++++++++-
>   3 files changed, 67 insertions(+), 1 deletion(-)
> 

Will you send a v2 with comments adresses ?