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SubjectRE: [PATCH v2] scsi: ufs: Remove pre-defined initial voltage values of device powers
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> 
> 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@linaro.org>
> Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Acked-by: Avri Altman <avri.altman@wdc.com>

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