linux-kernel - Re: [PATCH v2 2/9] dt-bindings: phy-qcom-qmp: Add UFS PHY reset

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Message-ID: <154904287525.169292.437324364877227469@swboyd.mtv.corp.google.com>
Date:   Fri, 01 Feb 2019 09:41:15 -0800
From:   Stephen Boyd <swboyd@...omium.org>
To:     Andy Gross <andy.gross@...aro.org>,
        Evan Green <evgreen@...omium.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Rob Herring <robh+dt@...nel.org>
Cc:     Can Guo <cang@...eaurora.org>,
        Douglas Anderson <dianders@...omium.org>,
        Asutosh Das <asutoshd@...eaurora.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 v2 2/9] dt-bindings: phy-qcom-qmp: Add UFS PHY reset

Quoting Evan Green (2019-01-23 14:11:30)
> 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>
> Reviewed-by: Rob Herring <robh@...nel.org>
> ---

Reviewed-by: Stephen Boyd <swboyd@...omium.org>