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

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Date:   Wed, 2 Dec 2020 16:22:34 +0800
From:   Stanley Chu <stanley.chu@...iatek.com>
To:     <nguyenb@...eaurora.org>
CC:     <linux-scsi@...r.kernel.org>, <martin.petersen@...cle.com>,
        <avri.altman@....com>, <alim.akhtar@...sung.com>,
        <jejb@...ux.ibm.com>, <beanhuo@...ron.com>,
        <asutoshd@...eaurora.org>, <cang@...eaurora.org>,
        <matthias.bgg@...il.com>, <bvanassche@....org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <bjorn.andersson@...aro.org>,
        <kuohong.wang@...iatek.com>, <peter.wang@...iatek.com>,
        <chun-hung.wu@...iatek.com>, <andy.teng@...iatek.com>,
        <chaotian.jing@...iatek.com>, <cc.chou@...iatek.com>,
        <jiajie.hao@...iatek.com>, <alice.chao@...iatek.com>
Subject: Re: [PATCH v2] scsi: ufs: Remove pre-defined initial voltage values
 of device powers

On Wed, 2020-12-02 at 00:19 -0800, nguyenb@...eaurora.org wrote:
> 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@...aro.org>
> > Signed-off-by: Stanley Chu <stanley.chu@...iatek.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;"?

Will remove it in next version.

Thanks for remind.

Stanley Chu

> 
> > 
> >  out: