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Subject: Re: [PATCH v2] scsi: ufs: Remove pre-defined initial voltage values
 of device powers
To:     Stanley Chu <stanley.chu@mediatek.com>, linux-scsi@vger.kernel.org,
        martin.petersen@oracle.com, avri.altman@wdc.com,
        alim.akhtar@samsung.com, jejb@linux.ibm.com
Cc:     beanhuo@micron.com, cang@codeaurora.org, matthias.bgg@gmail.com,
        bvanassche@acm.org, linux-mediatek@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        nguyenb@codeaurora.org, bjorn.andersson@linaro.org,
        kuohong.wang@mediatek.com, peter.wang@mediatek.com,
        chun-hung.wu@mediatek.com, andy.teng@mediatek.com,
        chaotian.jing@mediatek.com, cc.chou@mediatek.com,
        jiajie.hao@mediatek.com, alice.chao@mediatek.com
References: <20201201065114.1001-1-stanley.chu@mediatek.com>
From:   "Asutosh Das (asd)" <asutoshd@codeaurora.org>
Message-ID: <1ad24257-70cd-b16a-6ad4-c6705189a0e6@codeaurora.org>
Date:   Tue, 1 Dec 2020 08:43:27 -0800
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On 11/30/2020 10:51 PM, 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>
> ---

Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>

>   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;
>   
>   out:
> 


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