linux-kernel - Re: [PATCH v1 2/2] scsi: ufs: Support reading UFS's Vcc voltage from device tree

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Message-ID: <170592eceb26da041f276cf4ca33aaf2@codeaurora.org>
Date:   Mon, 14 Sep 2020 11:43:12 -0700
From:   nguyenb@...eaurora.org
To:     Avri Altman <Avri.Altman@....com>
Cc:     cang@...eaurora.org, asutoshd@...eaurora.org,
        martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        Alim Akhtar <alim.akhtar@...sung.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        YueHaibing <yuehaibing@...wei.com>,
        Bean Huo <beanhuo@...ron.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 2/2] scsi: ufs: Support reading UFS's Vcc voltage from
 device tree

On 2020-09-13 02:37, Avri Altman wrote:
>> 
>> The UFS specifications supports a range of Vcc operating voltage
>> from 2.4-3.6V depending on the device and manufacturers.
>> Allows selecting the UFS Vcc voltage level by setting the
>> UFS's entry vcc-voltage-level in the device tree. If UFS's
>> vcc-voltage-level setting is not found in the device tree,
>> use default values provided by the driver.
>> 
>> Signed-off-by: Can Guo <cang@...eaurora.org>
>> Signed-off-by: Asutosh Das <asutoshd@...eaurora.org>
>> Signed-off-by: Bao D. Nguyen <nguyenb@...eaurora.org>
>> ---
>>  drivers/scsi/ufs/ufshcd-pltfrm.c | 15 ++++++++++++---
>>  1 file changed, 12 insertions(+), 3 deletions(-)
>> 
>> diff --git a/drivers/scsi/ufs/ufshcd-pltfrm.c 
>> b/drivers/scsi/ufs/ufshcd-pltfrm.c
>> index 3db0af6..48f429c 100644
>> --- a/drivers/scsi/ufs/ufshcd-pltfrm.c
>> +++ b/drivers/scsi/ufs/ufshcd-pltfrm.c
>> @@ -104,10 +104,11 @@ static int ufshcd_parse_clock_info(struct 
>> ufs_hba
>> *hba)
>>  static int ufshcd_populate_vreg(struct device *dev, const char *name,
>>                 struct ufs_vreg **out_vreg)
>>  {
>> -       int ret = 0;
>> +       int len, ret = 0;
>>         char prop_name[MAX_PROP_SIZE];
>>         struct ufs_vreg *vreg = NULL;
>>         struct device_node *np = dev->of_node;
>> +       const __be32 *prop;
>> 
>>         if (!np) {
>>                 dev_err(dev, "%s: non DT initialization\n", __func__);
>> @@ -138,8 +139,16 @@ static int ufshcd_populate_vreg(struct device 
>> *dev,
>> const char *name,
>>                         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;
>> +                       prop = of_get_property(np, 
>> "vcc-voltage-level", &len);
>> +                       if (!prop || (len != (2 * sizeof(__be32)))) {
>> +                               dev_warn(dev, "%s vcc-voltage-level 
>> property.\n",
>> +                                       prop ? "invalid format" : 
>> "no");
>> +                               vreg->min_uV = UFS_VREG_VCC_MIN_UV;
>> +                               vreg->max_uV = UFS_VREG_VCC_MAX_UV;
>> +                       } else {
>> +                               vreg->min_uV = be32_to_cpup(&prop[0]);
>> +                               vreg->max_uV = be32_to_cpup(&prop[1]);
>> +                       }
>>                 }
>>         } else if (!strcmp(name, "vccq")) {
>>                 vreg->min_uV = UFS_VREG_VCCQ_MIN_UV;
>> --
> Maybe instead call ufshcd_populate_vreg with the new name,
> To not break the function flow, and just add another else if ?
Could you please clarify your comments? Are you suggesting to create a 
new function?
Thank you.