linux-kernel - [PATCH v3 0/2] spi: amlogic: meson-spicc: Use pinctrl to drive CLK line when idle

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Message-Id: <20221004-up-aml-fix-spi-v3-0-89de126fd163@baylibre.com>
Date:   Wed, 19 Oct 2022 16:01:02 +0200
From:   Amjad Ouled-Ameur <aouledameur@...libre.com>
To:     Mark Brown <broonie@...nel.org>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Kevin Hilman <khilman@...libre.com>,
        Rob Herring <robh+dt@...nel.org>
Cc:     Da Xue <da@...re.computer>, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-amlogic@...ts.infradead.org,
        Neil Armstrong <neil.armstrong@...aro.org>,
        linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Amjad Ouled-Ameur <aouledameur@...libre.com>
Subject: [PATCH v3 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.

Signed-off-by: Amjad Ouled-Ameur <aouledameur@...libre.com>
---
Changes in v3:
- Fixed documentation by removing pinctrl states as they are not mandatory.
- Link to v2: https://lore.kernel.org/r/20221004-up-aml-fix-spi-v2-0-3e8ae91a1925@baylibre.com

---
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       | 67 ++++++++++++++--------
 arch/arm64/boot/dts/amlogic/meson-gxl.dtsi         | 14 +++++
 drivers/spi/spi-meson-spicc.c                      | 39 ++++++++++++-
 3 files changed, 94 insertions(+), 26 deletions(-)
---
base-commit: aae703b02f92bde9264366c545e87cec451de471
change-id: 20221004-up-aml-fix-spi-c2bb7e78e603

Best regards,
-- 
Amjad Ouled-Ameur <aouledameur@...libre.com>