linux-kernel - [PATCH 1/2] dt-bindings: mtd: spi-nor: Add output-driver-strength property

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Message-Id: <20211004111529.211089-1-Alexander.Stein@tq-systems.com>
Date:   Mon,  4 Oct 2021 13:15:28 +0200
From:   Alexander Stein <Alexander.Stein@...systems.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Rob Herring <robh+dt@...nel.org>,
        Pratyush Yadav <p.yadav@...com>,
        Michael Walle <michael@...le.cc>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>
Cc:     Alexander Stein <alexander.stein@...tq-group.com>,
        linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] dt-bindings: mtd: spi-nor: Add output-driver-strength property

From: Alexander Stein <alexander.stein@...tq-group.com>

This property is for optimizing output voltage impedance and is
specific to each board.

Signed-off-by: Alexander Stein <alexander.stein@...tq-group.com>
---
I checked Micron and Macronix datasheets. Both have similar but not
identical supported values. Also the register locations are different.
For those reasons I decided to specify the Ohms value directly and let
the device specfic driver figure out if it is supported where to write
it to.
BTW: Are the Ohm values and the corresponding register bits standardized
somewhere?

 Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml
index ed590d7c6e37..7d7f20a741b5 100644
--- a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml
+++ b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml
@@ -72,6 +72,12 @@ properties:
       be used on such systems, to denote the absence of a reliable reset
       mechanism.
 
+  output-driver-strength:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      Output driver strength in Ohms which optimizes the impedance at Vcc/2
+      output voltage.
+
   label: true
 
   partitions:
-- 
2.25.1