linux-kernel - Re: [PATCH v1 1/8] dt-bindings: phy-qcom-qmp: Add UFS PHY reset

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Date:   Mon, 21 Jan 2019 18:21:37 -0600
From:   Rob Herring <robh@...nel.org>
To:     Evan Green <evgreen@...omium.org>
Cc:     Andy Gross <andy.gross@...aro.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Can Guo <cang@...eaurora.org>,
        Douglas Anderson <dianders@...omium.org>,
        Asutosh Das <asutoshd@...eaurora.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        Evan Green <evgreen@...omium.org>, devicetree@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/8] dt-bindings: phy-qcom-qmp: Add UFS PHY reset

On Fri, 11 Jan 2019 15:01:22 -0800, Evan Green wrote:
> Add a required reset to the SDM845 UFS phy to express the PHY reset
> bit inside the UFS controller register space. Before this change, this
> reset was not expressed in the DT, and the driver utilized two different
> callbacks (phy_init and phy_poweron) to implement a two-phase
> initialization procedure that involved deasserting this reset between
> init and poweron. This abused the two callbacks and diluted their
> purpose.
> 
> That scheme does not work as regulators cannot be turned off in
> phy_poweroff because they were turned on in init, rather than poweron.
> The net result is that regulators are left on in suspend that shouldn't
> be.
> 
> This new scheme gives the UFS reset to the PHY, so that it can fully
> initialize itself in a single callback. We can then turn regulators on
> during poweron and off during poweroff.
> 
> Signed-off-by: Evan Green <evgreen@...omium.org>
> ---
> I realize I'm not supposed to add a required property after the fact,
> but given that the UFS DT nodes that would use this binding are not
> yet upstream (and this would be the first), I was hoping to squeak by.
> 
>  Documentation/devicetree/bindings/phy/qcom-qmp-phy.txt | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 

Reviewed-by: Rob Herring <robh@...nel.org>