[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@linaro.org>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
---
 drivers/scsi/ufs/ufshcd-pltfrm.c | 16 ----------------
 1 file changed, 16 deletions(-)

On 2020-11-30 22:51, Stanley Chu wrote:
> 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>
> ---
>  drivers/scsi/ufs/ufshcd-pltfrm.c | 16 ----------------
>  1 file changed, 16 deletions(-)
> 
> diff --git a/drivers/scsi/ufs/ufshcd-pltfrm.c 
> b/drivers/scsi/ufs/ufshcd-pltfrm.c
> index a6f76399b3ae..09e2f04bf4f6 100644
> --- a/drivers/scsi/ufs/ufshcd-pltfrm.c
> +++ b/drivers/scsi/ufs/ufshcd-pltfrm.c
> @@ -133,22 +133,6 @@ static int ufshcd_populate_vreg(struct device
> *dev, const char *name,
>  		vreg->max_uA = 0;
>  	}
> 
> -	if (!strcmp(name, "vcc")) {
> -		if (of_property_read_bool(np, "vcc-supply-1p8")) {
> -			vreg->min_uV = UFS_VREG_VCC_1P8_MIN_UV;
> -			vreg->max_uV = UFS_VREG_VCC_1P8_MAX_UV;
> -		} else {
> -			vreg->min_uV = UFS_VREG_VCC_MIN_UV;
> -			vreg->max_uV = UFS_VREG_VCC_MAX_UV;
> -		}
> -	} else if (!strcmp(name, "vccq")) {
> -		vreg->min_uV = UFS_VREG_VCCQ_MIN_UV;
> -		vreg->max_uV = UFS_VREG_VCCQ_MAX_UV;
> -	} else if (!strcmp(name, "vccq2")) {
> -		vreg->min_uV = UFS_VREG_VCCQ2_MIN_UV;
> -		vreg->max_uV = UFS_VREG_VCCQ2_MAX_UV;
> -	}
> -
>  	goto out;
Do we need this "goto out;"?

> 
>  out: