From: Michael Walle <michael@walle.cc>
To: Alexander Stein <alexander.stein@ew.tq-group.com>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>,
Richard Weinberger <richard@nod.at>,
Vignesh Raghavendra <vigneshr@ti.com>,
Rob Herring <robh+dt@kernel.org>, Pratyush Yadav <p.yadav@ti.com>,
Tudor Ambarus <tudor.ambarus@microchip.com>,
linux-mtd@lists.infradead.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/2] dt-bindings: mtd: spi-nor: Add output-driver-strength property
Date: Tue, 12 Oct 2021 09:48:46 +0200 [thread overview]
Message-ID: <a347541ba3f8c76912d4afdb6dc64d4d@walle.cc> (raw)
In-Reply-To: <20211012061704.284214-1-alexander.stein@ew.tq-group.com>
Am 2021-10-12 08:17, schrieb Alexander Stein:
> This property is for optimizing output voltage impedance and is
> specific to each board. It overwrites the default set by the flash
> device. Various flash devices support different impedances.
>
> Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
> ---
> Changes in v2:
> * Updated the property description and the commit message accordingly
>
> Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml
> b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml
> index ed590d7c6e37..4c3c506a8853 100644
> --- a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml
> +++ b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml
> @@ -72,6 +72,14 @@ 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. This property overwrites the default set by the
> flash
> + device. This is board specific and should be determined by the
> + manufacturer. Various flash devices support different
> impedances.
Mh, this seems to be very tailored to this flash chip. Eg. the "Vcc/2",
is
this something specific to this flash or is this some kind of common
usage?
For example, Winbond flashes specifies the output driver strength in
percent.
Settings are 25%, 50%, 75%, 100% there.
I'd have to ask a hardware guy, if one could convert between these two
representations of the driver strength.
Rob, do you know how is this case ususally handled? Can there be
different
properties, like:
output-driver-strength-ohms
output-driver-strength-percent
or similar.
-michael
prev parent reply other threads:[~2021-10-12 7:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-12 6:17 [PATCH v2 1/2] dt-bindings: mtd: spi-nor: Add output-driver-strength property Alexander Stein
2021-10-12 6:17 ` [PATCH v2 2/2] mtd: spi-nor: micron-st: Add support for output-driver-strength for MT25Q Alexander Stein
2021-10-12 7:48 ` Michael Walle [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=a347541ba3f8c76912d4afdb6dc64d4d@walle.cc \
--to=michael@walle.cc \
--cc=alexander.stein@ew.tq-group.com \
--cc=devicetree@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mtd@lists.infradead.org \
--cc=miquel.raynal@bootlin.com \
--cc=p.yadav@ti.com \
--cc=richard@nod.at \
--cc=robh+dt@kernel.org \
--cc=tudor.ambarus@microchip.com \
--cc=vigneshr@ti.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).