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Date:   Wed, 13 Feb 2019 11:05:28 +0100
From:   Marc Gonzalez <>
To:     Mark Brown <>
Cc:     SCSI <>,
        LKML <>,
        Jeffrey Hugo <>,
        Bjorn Andersson <>,
        Evan Green <>,
        Douglas Anderson <>,
        Alim Akhtar <>,
        Avri Altman <>,
        Pedro Sousa <>,
        Joao Pinto <>,
        Liam Girdwood <>,
        Rob Herring <>,
        Bart Van Assche <>,
        Stanislav Nijnikov <>,
        Alex Lemberg <>,
        Ohad Sharabi <>,
        Venkat Gopalakrishnan <>,
        Subhash Jadavani <>,
        Yaniv Gardi <>,
        Raviv Shvili <>,
        Hannes Reinecke <>, Kyuho Choi <>,
        Martin Petersen <>
Subject: Re: [PATCH v5 1/2] scsi: ufs: Do not disable vccq in UFSHC driver

On 11/02/2019 18:23, Mark Brown wrote:

> On Mon, Feb 11, 2019 at 02:32:15PM +0100, Marc Gonzalez wrote:
>> Unfortunately, this optimization breaks UFS on systems where vccq
>> powers not only the Flash chip, but the host controller as well,
>> such as APQ8098 MEDIABOX or MTP8998.
>> In my opinion, the rationale for the original patch is questionable.
>> If neither the UFSHC, nor the Flash chip, require any load from vccq,
>> then that power rail should simply not be specified at all in the DT.
> If the supply is physically connected it should be valid to represent
> this in DT regardless of how or if the supply gets used at runtime.
> However it does sound like this support needs to be better thought
> through to make sure we have represented the supplies to the flash chip
> and the controller separately - it seems like right now there's no
> tracking of the supplies needed for the controller and the assumption is
> that only the flash chip needs managing which is breaking things.

As far as I'm aware, the conflation of host controller with their respective
storage medium occurs across several techs: UFS, NAND, SDHC, EMMC.

There might be room for improvement, but I don't think these considerations
should hold up this series, which fixes something that is broken *today*.

UFS reviewers (Alim, Avri, Pedro), can I get at least one Acked-by to remove
this small power optimization that breaks UFS on my system?


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