linux-kernel - [PATCH v6 1/2] dt-bindings: i2c: add bus-reset-gpios property

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Date:   Wed, 15 Nov 2023 16:57:52 +1300
From:   Chris Packham <chris.packham@...iedtelesis.co.nz>
To:     wsa@...nel.org, andi.shyti@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        gregory.clement@...tlin.com
Cc:     linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Chris Packham <chris.packham@...iedtelesis.co.nz>
Subject: [PATCH v6 1/2] dt-bindings: i2c: add bus-reset-gpios property

Add bus-reset-gpios and bus-reset-duration-us properties to the binding
description for i2c busses. These can be used to describe hardware where
a common reset GPIO is connected to all downstream devices on and I2C
bus. This reset will be asserted then released before the downstream
devices on the bus are probed.

Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
---

Notes:
    I expect the first reaction to this will be a request to convert the
    binding to dtschema. I can attempt such a conversion but given it's one
    of the more core bindings I expect others may have strong opinions. I
    didn't want to start a conversion without hearing those opinions (or if
    I could get away without doing the conversion). It's also likely to spin
    off a whole lot of work to bring existing device trees into line.
    
    Changes in v6:
    - Retarget changes at the i2c core instead of an individual driver
    Changes in v5:
    - Rename reset-gpios and reset-duration-us to bus-reset-gpios and
      bus-reset-duration-us as requested by Wolfram
    Changes in v4:
    - Add r-by from Krzysztof
    Changes in v3:
    - Rename reset-delay-us to reset-duration-us to better reflect its
      purpose
    - Add default: for reset-duration-us
    - Add description: for reset-gpios
    Changes in v2:
    - Update commit message
    - Add reset-delay-us property

 Documentation/devicetree/bindings/i2c/i2c.txt | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Documentation/devicetree/bindings/i2c/i2c.txt b/Documentation/devicetree/bindings/i2c/i2c.txt
index fc3dd7ec0445..3f95d71b9985 100644
--- a/Documentation/devicetree/bindings/i2c/i2c.txt
+++ b/Documentation/devicetree/bindings/i2c/i2c.txt
@@ -99,6 +99,14 @@ wants to support one of the below features, it should adapt these bindings.
 	indicates that the system is accessible via this bus as an endpoint for
 	MCTP over I2C transport.
 
+- bus-reset-gpios:
+	GPIO pin providing a common reset for all downstream devices. This GPIO
+	will be asserted then released before the downstream devices are probed.
+
+- bus-reset-duration-us:
+	Reset duration in us.
+	default: 1
+
 Required properties (per child device)
 --------------------------------------
 
-- 
2.42.0