linux-kernel - RE: [PATCH v2] scsi: ufs: Remove pre-defined initial voltage values of device powers

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Date:   Tue, 1 Dec 2020 07:01:23 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Stanley Chu <stanley.chu@...iatek.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "alim.akhtar@...sung.com" <alim.akhtar@...sung.com>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>
CC:     "beanhuo@...ron.com" <beanhuo@...ron.com>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        "cang@...eaurora.org" <cang@...eaurora.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "bvanassche@....org" <bvanassche@....org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "nguyenb@...eaurora.org" <nguyenb@...eaurora.org>,
        "bjorn.andersson@...aro.org" <bjorn.andersson@...aro.org>,
        "kuohong.wang@...iatek.com" <kuohong.wang@...iatek.com>,
        "peter.wang@...iatek.com" <peter.wang@...iatek.com>,
        "chun-hung.wu@...iatek.com" <chun-hung.wu@...iatek.com>,
        "andy.teng@...iatek.com" <andy.teng@...iatek.com>,
        "chaotian.jing@...iatek.com" <chaotian.jing@...iatek.com>,
        "cc.chou@...iatek.com" <cc.chou@...iatek.com>,
        "jiajie.hao@...iatek.com" <jiajie.hao@...iatek.com>,
        "alice.chao@...iatek.com" <alice.chao@...iatek.com>
Subject: RE: [PATCH v2] scsi: ufs: Remove pre-defined initial voltage values
 of device powers

> 
> UFS specficication allows different VCC configurations for UFS devices,
> for example,
>         (1). 2.70V - 3.60V (Activated by default in UFS core driver)
>         (2). 1.70V - 1.95V (Activated if "vcc-supply-1p8" is declared in
>                           device tree)
>         (3). 2.40V - 2.70V (Supported since UFS 3.x)
> 
> With the introduction of UFS 3.x products, an issue is happening that
> UFS driver will use wrong "min_uV-max_uV" values to configure the
> voltage of VCC regulator on UFU 3.x products with the configuration (3)
> used.
> 
> To solve this issue, we simply remove pre-defined initial VCC voltage
> values in UFS core driver with below reasons,
> 
> 1. UFS specifications do not define how to detect the VCC configuration
>    supported by attached device.
> 
> 2. Device tree already supports standard regulator properties.
> 
> Therefore VCC voltage shall be defined correctly in device tree, and
> shall not changed by UFS driver. What UFS driver needs to do is simply
> enable or disable the VCC regulator only.
> 
> Similar change is applied to VCCQ and VCCQ2 as well.
> 
> Note that we keep struct ufs_vreg unchanged. This is allow vendors to
> configure proper min_uV and max_uV of any regulators to make
> regulator_set_voltage() works during regulator toggling flow.
> Without specific vendor configurations, min_uV and max_uV will be NULL
> by default and UFS core driver will enable or disable the regulator
> only without adjusting its voltage.
> 
> Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> Signed-off-by: Stanley Chu <stanley.chu@...iatek.com>
Acked-by: Avri Altman <avri.altman@....com>