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

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Message-Id: <20220809172017.215412-1-aouledameur@baylibre.com>
Date:   Tue,  9 Aug 2022 19:20:15 +0200
From:   Amjad Ouled-Ameur <aouledameur@...libre.com>
To:     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,
        Amjad Ouled-Ameur <aouledameur@...libre.com>
Subject: [PATCH 0/2] spi: amlogic: meson-spicc: Use pinctrl to drive CLK line when idle

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(-)

-- 
2.37.1