linux-kernel - Re: [PATCH] scsi: ufs-qcom: add number of lanes per direction

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Message-ID: <20180209022915.2kki7avsia2k7tjp@rob-hp-laptop>
Date:   Thu, 8 Feb 2018 20:29:15 -0600
From:   Rob Herring <robh@...nel.org>
To:     Can Guo <cang@...eaurora.org>
Cc:     subhashj@...eaurora.org, asutoshd@...eaurora.org,
        vivek.gautam@...eaurora.org, rnayak@...eaurora.org,
        vinholikatti@...il.com, jejb@...ux.vnet.ibm.com,
        martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        Gilad Broner <gbroner@...eaurora.org>,
        Mark Rutland <mark.rutland@....com>,
        Venkat Gopalakrishnan <venkatg@...eaurora.org>,
        Noa Rubens <noag@...eaurora.org>,
        Sujit Reddy Thumma <sthumma@...eaurora.org>,
        Maya Erez <merez@...eaurora.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] scsi: ufs-qcom: add number of lanes per direction

On Mon, Feb 05, 2018 at 08:02:07PM +0800, Can Guo wrote:
> From: Gilad Broner <gbroner@...eaurora.org>
> 
> Different platforms may have different number of lanes for the UFS link.
> Add parameter to device tree specifying how many lanes should be
> configured for the UFS link. And don't print err message for clocks
> that are optional, this leads to unnecessary confusion about failure.
> 
> Signed-off-by: Gilad Broner <gbroner@...eaurora.org>
> Signed-off-by: Subhash Jadavani <subhashj@...eaurora.org>
> Signed-off-by: Can Guo <cang@...eaurora.org>
> 
> diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> index 5357919..4cee3f9 100644
> --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> @@ -31,6 +31,9 @@ Optional properties:
>  			  defined or a value in the array is "0" then it is assumed
>  			  that the frequency is set by the parent clock or a
>  			  fixed rate clock source.
> +- lanes-per-direction:	number of lanes available per direction - either 1 or 2.
> +			Note that it is assume same number of lanes is used both directions at once.

Seems reasonable until someone does not make things symmetrical. We 
should design for that case.

> +			If not specified, default is 2 lanes per direction.
>  
>  Note: If above properties are not defined it can be assumed that the supply
>  regulators or clocks are always on.