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From: Rob Herring <robh@kernel.org>
To: Alexander Stein <Alexander.Stein@tq-systems.com>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	Pratyush Yadav <p.yadav@ti.com>, Michael Walle <michael@walle.cc>,
	Tudor Ambarus <tudor.ambarus@microchip.com>,
	Alexander Stein <alexander.stein@ew.tq-group.com>,
	linux-mtd@lists.infradead.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: mtd: spi-nor: Add output-driver-strength property
Date: Tue, 12 Oct 2021 07:52:17 -0500	[thread overview]
Message-ID: <YWWFAXeekLS80bOR@robh.at.kernel.org> (raw)
In-Reply-To: <20211004111529.211089-1-Alexander.Stein@tq-systems.com>

On Mon, Oct 04, 2021 at 01:15:28PM +0200, Alexander Stein wrote:
> From: Alexander Stein <alexander.stein@ew.tq-group.com>
> 
> This property is for optimizing output voltage impedance and is
> specific to each board.
> 
> Signed-off-by: Alexander Stein <alexander.stein@ew.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.

Use a standard unit suffix.

Though, specifying 'drive strength' in ohms rather than amps is a bit 
strange.

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

WARNING: multiple messages have this Message-ID (diff)
From: Rob Herring <robh@kernel.org>
To: Alexander Stein <Alexander.Stein@tq-systems.com>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	Pratyush Yadav <p.yadav@ti.com>, Michael Walle <michael@walle.cc>,
	Tudor Ambarus <tudor.ambarus@microchip.com>,
	Alexander Stein <alexander.stein@ew.tq-group.com>,
	linux-mtd@lists.infradead.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: mtd: spi-nor: Add output-driver-strength property
Date: Tue, 12 Oct 2021 07:52:17 -0500	[thread overview]
Message-ID: <YWWFAXeekLS80bOR@robh.at.kernel.org> (raw)
In-Reply-To: <20211004111529.211089-1-Alexander.Stein@tq-systems.com>

On Mon, Oct 04, 2021 at 01:15:28PM +0200, Alexander Stein wrote:
> From: Alexander Stein <alexander.stein@ew.tq-group.com>
> 
> This property is for optimizing output voltage impedance and is
> specific to each board.
> 
> Signed-off-by: Alexander Stein <alexander.stein@ew.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.

Use a standard unit suffix.

Though, specifying 'drive strength' in ohms rather than amps is a bit 
strange.

  parent reply	other threads:[~2021-10-12 12:53 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-04 11:15 [PATCH 1/2] dt-bindings: mtd: spi-nor: Add output-driver-strength property Alexander Stein
2021-10-04 11:15 ` [PATCH 2/2] mtd: spi-nor: micron-st: Add support for output-driver-strength Alexander Stein
2021-10-04 11:26   ` Tudor.Ambarus
2021-10-04 11:26     ` Tudor.Ambarus
2021-10-08 11:18   ` Pratyush Yadav
2021-10-08 11:18     ` Pratyush Yadav
2021-10-04 11:25 ` [PATCH 1/2] dt-bindings: mtd: spi-nor: Add output-driver-strength property Tudor.Ambarus
2021-10-04 11:25   ` Tudor.Ambarus
2021-10-05 12:26 ` Rob Herring
2021-10-05 12:26   ` Rob Herring
2021-10-12 12:52 ` Rob Herring [this message]
2021-10-12 12:52   ` Rob Herring

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