linux-kernel - Re: [PATCH] dt-bindings: i2c: Add armada-38x i2c binding

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Date:   Sun, 24 Sep 2017 21:44:21 +0000
From:   Kalyan Kinthada <Kalyan.Kinthada@...iedtelesis.co.nz>
To:     Gregory CLEMENT <gregory.clement@...e-electrons.com>
CC:     "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "wsa@...-dreams.de" <wsa@...-dreams.de>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "pawel.moll@....com" <pawel.moll@....com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
        "galak@...eaurora.org" <galak@...eaurora.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Chris Packham <Chris.Packham@...iedtelesis.co.nz>
Subject: Re: [PATCH] dt-bindings: i2c: Add armada-38x i2c binding

Hi Gregory,

I got this information from Armada-38x functional errata document.

I can add the "marvell,mv78230-i2c" compatible string to the appropriate  device tree files 
but the i2c-mv64xxx driver enables an additional  feature (offload i2c transactions)
based on the compatible string "marvell,mv78230-i2c".

I am not sure if this feature (offload i2c transactions) should be enabled for Armada-38x devices.
That is the reason I felt for the need of a new compatible string specifically for Armada-38x SoCs.

Thanks,
Kalyan
________________________________________
From: Gregory CLEMENT <gregory.clement@...e-electrons.com>
Sent: Friday, 22 September 2017 7:30 p.m.
To: Kalyan Kinthada
Cc: devicetree@...r.kernel.org; wsa@...-dreams.de; robh+dt@...nel.org; pawel.moll@....com; mark.rutland@....com; ijc+devicetree@...lion.org.uk; galak@...eaurora.org; linux-i2c@...r.kernel.org; linux-kernel@...r.kernel.org; Chris Packham
Subject: Re: [PATCH] dt-bindings: i2c: Add armada-38x i2c binding

Hi Kalyan,

 On ven., sept. 22 2017, Kalyan Kinthada <kalyan.kinthada@...iedtelesis.co.nz> wrote:

> All armada-38x variants(380, 385, 388) SoCs have an issue
> in i2c controller which violates the i2c repeated start timing.

Did you had an issue with one of the SoC ?
If yes what was your setting ?
On my side I never managed to have this sort of issue on Armada 38x.

>
> This errata is fixed in the i2c-mv64xxx driver but enabled
> only for devices with compatible string "marvell,mv78230-i2c".

In this case why not just adding the "marvell,mv78230-i2c" as compatible
string in the appropriate device tree files ?

Gregory

>
> This patch introduces a new compatible string
> "marvell,armada-38x-i2c" for the i2c controller on armada-38x SoCs
> so that the workaound is enabled.

>
> Signed-off-by: Kalyan Kinthada <kalyan.kinthada@...iedtelesis.co.nz>
> ---
>  Documentation/devicetree/bindings/i2c/i2c-mv64xxx.txt | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-mv64xxx.txt b/Documentation/devicetree/bindings/i2c/i2c-mv64xxx.txt
> index 5c30026921..fc100b6bdb 100644
> --- a/Documentation/devicetree/bindings/i2c/i2c-mv64xxx.txt
> +++ b/Documentation/devicetree/bindings/i2c/i2c-mv64xxx.txt
> @@ -14,6 +14,7 @@ Required properties :
>                           very rare, initial version of the SoC which
>                           had broken offload support.  Linux
>                           auto-detects this and sets it appropriately.
> +                     - "marvell,armada-38x-i2c"
>   - interrupts      : The interrupt number
>
>  Optional properties :
> --
> 2.14.1
>

--
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com