[PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for UFS

[PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for UFS

[Bao D. Nguyen]

UFS's specifications supports a range of Vcc operating
voltage levels. Add documentation for the UFS's Vcc voltage
levels setting.

Signed-off-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>
---
 Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
index 415ccdd..7257b32 100644
--- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
+++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
@@ -23,6 +23,8 @@ Optional properties:
                           with "phys" attribute, provides phandle to UFS PHY node
 - vdd-hba-supply        : phandle to UFS host controller supply regulator node
 - vcc-supply            : phandle to VCC supply regulator node
+- vcc-voltage-level     : specifies voltage levels for VCC supply.
+                          Should be specified in pairs (min, max), units uV.
 - vccq-supply           : phandle to VCCQ supply regulator node
 - vccq2-supply          : phandle to VCCQ2 supply regulator node
 - vcc-supply-1p8        : For embedded UFS devices, valid VCC range is 1.7-1.95V
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

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

[Bao D. Nguyen]

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@codeaurora.org>
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.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;
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

RE: [PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for UFS

[Avri Altman]

> 
> 
> UFS's specifications supports a range of Vcc operating
> voltage levels. Add documentation for the UFS's Vcc voltage
> levels setting.
> 
> Signed-off-by: Can Guo <cang@codeaurora.org>
> Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
> Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>
> ---
>  Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> index 415ccdd..7257b32 100644
> --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> @@ -23,6 +23,8 @@ Optional properties:
>                            with "phys" attribute, provides phandle to UFS PHY node
>  - vdd-hba-supply        : phandle to UFS host controller supply regulator node
>  - vcc-supply            : phandle to VCC supply regulator node
> +- vcc-voltage-level     : specifies voltage levels for VCC supply.
For ufs3.1+ devices

> +                          Should be specified in pairs (min, max), units uV.
>  - vccq-supply           : phandle to VCCQ supply regulator node
>  - vccq2-supply          : phandle to VCCQ2 supply regulator node
>  - vcc-supply-1p8        : For embedded UFS devices, valid VCC range is 1.7-1.95V
> --
Why are you removing all other docs?
They are still relevant for non ufs3.1 devices.

RE: [PATCH v1 2/2] scsi: ufs: Support reading UFS's Vcc voltage from device tree

[Avri Altman]

 
> 
> 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@codeaurora.org>
> Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
> Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.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 ?

Re: [PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for UFS

[nguyenb]

On 2020-09-13 02:35, Avri Altman wrote:
>> 
>> 
>> UFS's specifications supports a range of Vcc operating
>> voltage levels. Add documentation for the UFS's Vcc voltage
>> levels setting.
>> 
>> Signed-off-by: Can Guo <cang@codeaurora.org>
>> Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
>> Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>
>> ---
>>  Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt | 2 ++
>>  1 file changed, 2 insertions(+)
>> 
>> diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> index 415ccdd..7257b32 100644
>> --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> @@ -23,6 +23,8 @@ Optional properties:
>>                            with "phys" attribute, provides phandle to 
>> UFS PHY node
>>  - vdd-hba-supply        : phandle to UFS host controller supply 
>> regulator node
>>  - vcc-supply            : phandle to VCC supply regulator node
>> +- vcc-voltage-level     : specifies voltage levels for VCC supply.
> For ufs3.1+ devices
Thanks for the comments, Avri.
I am not clear what this comment means. Could you please clarify?
> 
>> +                          Should be specified in pairs (min, max), 
>> units uV.
>>  - vccq-supply           : phandle to VCCQ supply regulator node
>>  - vccq2-supply          : phandle to VCCQ2 supply regulator node
>>  - vcc-supply-1p8        : For embedded UFS devices, valid VCC range 
>> is 1.7-1.95V
>> --
> Why are you removing all other docs?
> They are still relevant for non ufs3.1 devices.
I did not remove anything. You may be confused by the "-" used as 
listing in the original document.

Re: [PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for UFS

[Rob Herring]

On Mon, Aug 31, 2020 at 11:00:47PM -0700, Bao D. Nguyen wrote:
> UFS's specifications supports a range of Vcc operating
> voltage levels. Add documentation for the UFS's Vcc voltage
> levels setting.
> 
> Signed-off-by: Can Guo <cang@codeaurora.org>
> Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
> Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>
> ---
>  Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> index 415ccdd..7257b32 100644
> --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> @@ -23,6 +23,8 @@ Optional properties:
>                            with "phys" attribute, provides phandle to UFS PHY node
>  - vdd-hba-supply        : phandle to UFS host controller supply regulator node
>  - vcc-supply            : phandle to VCC supply regulator node
> +- vcc-voltage-level     : specifies voltage levels for VCC supply.
> +                          Should be specified in pairs (min, max), units uV.

The expectation is the regulator pointed to by 'vcc-supply' has the 
voltage constraints. Those constraints are supposed to be the board 
constraints, not the regulator operating design constraints. If that 
doesn't work for your case, then it should be addressed in a common way 
for the regulator binding.

Also, properties with units must have a unit suffix.

Rob

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

[nguyenb]

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@codeaurora.org>
>> Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
>> Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.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.

Re: [PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for UFS

[Bjorn Andersson]

On Tue 01 Sep 01:00 CDT 2020, Bao D. Nguyen wrote:

> UFS's specifications supports a range of Vcc operating
> voltage levels. Add documentation for the UFS's Vcc voltage
> levels setting.
> 
> Signed-off-by: Can Guo <cang@codeaurora.org>
> Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
> Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>
> ---
>  Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> index 415ccdd..7257b32 100644
> --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> @@ -23,6 +23,8 @@ Optional properties:
>                            with "phys" attribute, provides phandle to UFS PHY node
>  - vdd-hba-supply        : phandle to UFS host controller supply regulator node
>  - vcc-supply            : phandle to VCC supply regulator node
> +- vcc-voltage-level     : specifies voltage levels for VCC supply.
> +                          Should be specified in pairs (min, max), units uV.

What exactly are these pairs representing?

Is this supposed to be 3 pairs of (min,max) for vcc, vcc and vccq2 to be
passed into a regulator_set_voltage() for each regulator?

Or are these some sort of "operating points" for the vcc-supply?

Regards,
Bjorn

>  - vccq-supply           : phandle to VCCQ supply regulator node
>  - vccq2-supply          : phandle to VCCQ2 supply regulator node
>  - vcc-supply-1p8        : For embedded UFS devices, valid VCC range is 1.7-1.95V
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
> 

RE: [PATCH v1 2/2] scsi: ufs: Support reading UFS's Vcc voltage from device tree

[Avri Altman]

> > 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.
No, just call ufshcd_populate_vreg with the new name, e.g. something like:

diff --git a/drivers/scsi/ufs/ufshcd-pltfrm.c b/drivers/scsi/ufs/ufshcd-pltfrm.c
index 3db0af6..9798d4c 100644
--- a/drivers/scsi/ufs/ufshcd-pltfrm.c
+++ b/drivers/scsi/ufs/ufshcd-pltfrm.c
@@ -141,6 +141,8 @@ static int ufshcd_populate_vreg(struct device *dev, const char *name,
                        vreg->min_uV = UFS_VREG_VCC_MIN_UV;
                        vreg->max_uV = UFS_VREG_VCC_MAX_UV;
                }
+       } else if (!strcmp(name, "vcc-voltage-level")) {
+               /* add your changes here */
        } else if (!strcmp(name, "vccq")) {
                vreg->min_uV = UFS_VREG_VCCQ_MIN_UV;
                vreg->max_uV = UFS_VREG_VCCQ_MAX_UV;
@@ -177,8 +179,12 @@ static int ufshcd_parse_regulator_info(struct ufs_hba *hba)
                goto out;
 
        err = ufshcd_populate_vreg(dev, "vcc", &info->vcc);
-       if (err)
-               goto out;
+       if (err) {
+               err = ufshcd_populate_vreg(dev, "vcc-voltage-level",
+                                          &info->vcc);
+               if (err)
+                       goto out;
+       }
 
        err = ufshcd_populate_vreg(dev, "vccq", &info->vccq);
        if (err)

Re: [PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for UFS

[nguyenb]

On 2020-09-14 11:35, Rob Herring wrote:
> On Mon, Aug 31, 2020 at 11:00:47PM -0700, Bao D. Nguyen wrote:
>> UFS's specifications supports a range of Vcc operating
>> voltage levels. Add documentation for the UFS's Vcc voltage
>> levels setting.
>> 
>> Signed-off-by: Can Guo <cang@codeaurora.org>
>> Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
>> Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>
>> ---
>>  Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt | 2 ++
>>  1 file changed, 2 insertions(+)
>> 
>> diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt 
>> b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> index 415ccdd..7257b32 100644
>> --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> @@ -23,6 +23,8 @@ Optional properties:
>>                            with "phys" attribute, provides phandle to 
>> UFS PHY node
>>  - vdd-hba-supply        : phandle to UFS host controller supply 
>> regulator node
>>  - vcc-supply            : phandle to VCC supply regulator node
>> +- vcc-voltage-level     : specifies voltage levels for VCC supply.
>> +                          Should be specified in pairs (min, max), 
>> units uV.
> 
> The expectation is the regulator pointed to by 'vcc-supply' has the
> voltage constraints. Those constraints are supposed to be the board
> constraints, not the regulator operating design constraints. If that
> doesn't work for your case, then it should be addressed in a common way
> for the regulator binding.
The UFS regulator has a min_uV and max_uV limits. Currently, the min and 
max are hardcoded
to UFS2.1 Spec allowed values of 2.7V and 3.6V respectively.
With this change, I am trying to fix a couple issues:
1. The 2.7V min value only applies to UFS2.1 devices. with UFS3.0+ 
devices, the VCC min should be 2.4V.
Hardcoding the min_uV to 2.7V does not work for UFS3.0+ devices.

2. Allow users to select a different Vcc voltage within the allowed 
range.
Using the min value, the UFS device is operating at marginal Vcc 
voltage.
In addition the PMIC and the board designs may add some variables 
especially at extreme
temperatures. We observe stability issues when using the min Vcc 
voltage.

> 
> Also, properties with units must have a unit suffix.
Yes, I agree.
> 
> Rob

Re: [PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for UFS

[nguyenb]

On 2020-09-14 21:41, Bjorn Andersson wrote:
> On Tue 01 Sep 01:00 CDT 2020, Bao D. Nguyen wrote:
> 
>> UFS's specifications supports a range of Vcc operating
>> voltage levels. Add documentation for the UFS's Vcc voltage
>> levels setting.
>> 
>> Signed-off-by: Can Guo <cang@codeaurora.org>
>> Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
>> Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>
>> ---
>>  Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt | 2 ++
>>  1 file changed, 2 insertions(+)
>> 
>> diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt 
>> b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> index 415ccdd..7257b32 100644
>> --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> @@ -23,6 +23,8 @@ Optional properties:
>>                            with "phys" attribute, provides phandle to 
>> UFS PHY node
>>  - vdd-hba-supply        : phandle to UFS host controller supply 
>> regulator node
>>  - vcc-supply            : phandle to VCC supply regulator node
>> +- vcc-voltage-level     : specifies voltage levels for VCC supply.
>> +                          Should be specified in pairs (min, max), 
>> units uV.
> 
> What exactly are these pairs representing?
The pair is the min and max Vcc voltage request to the PMIC chip.
As a result, the regulator output voltage would only be in this range.

> 
> Is this supposed to be 3 pairs of (min,max) for vcc, vcc and vccq2 to 
> be
> passed into a regulator_set_voltage() for each regulator?
Yes, that's right. I should include the other power supplies in this 
change as well.
> 
> Or are these some sort of "operating points" for the vcc-supply?
> 
> Regards,
> Bjorn
> 
>>  - vccq-supply           : phandle to VCCQ supply regulator node
>>  - vccq2-supply          : phandle to VCCQ2 supply regulator node
>>  - vcc-supply-1p8        : For embedded UFS devices, valid VCC range 
>> is 1.7-1.95V
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
>> Forum,
>> a Linux Foundation Collaborative Project
>> 

Re: [PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for UFS

[Bjorn Andersson]

On Tue 15 Sep 03:14 CDT 2020, nguyenb@codeaurora.org wrote:

> On 2020-09-14 21:41, Bjorn Andersson wrote:
> > On Tue 01 Sep 01:00 CDT 2020, Bao D. Nguyen wrote:
> > 
> > > UFS's specifications supports a range of Vcc operating
> > > voltage levels. Add documentation for the UFS's Vcc voltage
> > > levels setting.
> > > 
> > > Signed-off-by: Can Guo <cang@codeaurora.org>
> > > Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
> > > Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>
> > > ---
> > >  Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt | 2 ++
> > >  1 file changed, 2 insertions(+)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> > > b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> > > index 415ccdd..7257b32 100644
> > > --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> > > +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> > > @@ -23,6 +23,8 @@ Optional properties:
> > >                            with "phys" attribute, provides phandle
> > > to UFS PHY node
> > >  - vdd-hba-supply        : phandle to UFS host controller supply
> > > regulator node
> > >  - vcc-supply            : phandle to VCC supply regulator node
> > > +- vcc-voltage-level     : specifies voltage levels for VCC supply.
> > > +                          Should be specified in pairs (min, max),
> > > units uV.
> > 
> > What exactly are these pairs representing?
> The pair is the min and max Vcc voltage request to the PMIC chip.
> As a result, the regulator output voltage would only be in this range.
> 

If you have static min/max voltage constraints for a device on a
particular board the right way to handle this is to adjust the board's
regulator-min-microvolt and regulator-max-microvolt accordingly - and
not call regulator_set_voltage() from the river at all.

In other words, you shouldn't add this new property to describe
something already described in the node vcc-supply points to.

Regards,
Bjorn

> > 
> > Is this supposed to be 3 pairs of (min,max) for vcc, vcc and vccq2 to be
> > passed into a regulator_set_voltage() for each regulator?
> Yes, that's right. I should include the other power supplies in this change
> as well.
> > 
> > Or are these some sort of "operating points" for the vcc-supply?
> > 
> > Regards,
> > Bjorn
> > 
> > >  - vccq-supply           : phandle to VCCQ supply regulator node
> > >  - vccq2-supply          : phandle to VCCQ2 supply regulator node
> > >  - vcc-supply-1p8        : For embedded UFS devices, valid VCC range
> > > is 1.7-1.95V
> > > --
> > > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> > > Forum,
> > > a Linux Foundation Collaborative Project
> > > 

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

[Bjorn Andersson]

On Tue 01 Sep 01:00 CDT 2020, Bao D. Nguyen 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.
> 

As stated in the reply to patch 1, this is not the right approach.  As
long as you have static min/max values requested by the driver you
should rely on the board's constraints for the regulator levels and
instead remove the min_uV/max_uV code from the driver.

Thanks,
Bjorn

> Signed-off-by: Can Guo <cang@codeaurora.org>
> Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
> Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.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;
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
> 

Re: [PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for UFS

[nguyenb]

On 2020-09-15 06:43, Bjorn Andersson wrote:
> On Tue 15 Sep 03:14 CDT 2020, nguyenb@codeaurora.org wrote:
> 
>> On 2020-09-14 21:41, Bjorn Andersson wrote:
>> > On Tue 01 Sep 01:00 CDT 2020, Bao D. Nguyen wrote:
>> >
>> > > UFS's specifications supports a range of Vcc operating
>> > > voltage levels. Add documentation for the UFS's Vcc voltage
>> > > levels setting.
>> > >
>> > > Signed-off-by: Can Guo <cang@codeaurora.org>
>> > > Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
>> > > Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>
>> > > ---
>> > >  Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt | 2 ++
>> > >  1 file changed, 2 insertions(+)
>> > >
>> > > diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> > > b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> > > index 415ccdd..7257b32 100644
>> > > --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> > > +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> > > @@ -23,6 +23,8 @@ Optional properties:
>> > >                            with "phys" attribute, provides phandle
>> > > to UFS PHY node
>> > >  - vdd-hba-supply        : phandle to UFS host controller supply
>> > > regulator node
>> > >  - vcc-supply            : phandle to VCC supply regulator node
>> > > +- vcc-voltage-level     : specifies voltage levels for VCC supply.
>> > > +                          Should be specified in pairs (min, max),
>> > > units uV.
>> >
>> > What exactly are these pairs representing?
>> The pair is the min and max Vcc voltage request to the PMIC chip.
>> As a result, the regulator output voltage would only be in this range.
>> 
> 
> If you have static min/max voltage constraints for a device on a
> particular board the right way to handle this is to adjust the board's
> regulator-min-microvolt and regulator-max-microvolt accordingly - and
> not call regulator_set_voltage() from the river at all.
> 
> In other words, you shouldn't add this new property to describe
> something already described in the node vcc-supply points to.
> 
> Regards,
> Bjorn
Thank you all for your comments. The current driver hardcoding 2.7V Vcc 
min voltage
does not work for UFS3.0+ devices according to the UFS device JEDEC 
spec. However, we will
try to address it in a different way.

Regards,
Bao

> 
>> >
>> > Is this supposed to be 3 pairs of (min,max) for vcc, vcc and vccq2 to be
>> > passed into a regulator_set_voltage() for each regulator?
>> Yes, that's right. I should include the other power supplies in this 
>> change
>> as well.
>> >
>> > Or are these some sort of "operating points" for the vcc-supply?
>> >
>> > Regards,
>> > Bjorn
>> >
>> > >  - vccq-supply           : phandle to VCCQ supply regulator node
>> > >  - vccq2-supply          : phandle to VCCQ2 supply regulator node
>> > >  - vcc-supply-1p8        : For embedded UFS devices, valid VCC range
>> > > is 1.7-1.95V
>> > > --
>> > > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
>> > > Forum,
>> > > a Linux Foundation Collaborative Project
>> > >

Re: [PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for UFS

[Bjorn Andersson]

On Tue 15 Sep 16:47 UTC 2020, nguyenb@codeaurora.org wrote:

> On 2020-09-15 06:43, Bjorn Andersson wrote:
> > On Tue 15 Sep 03:14 CDT 2020, nguyenb@codeaurora.org wrote:
> > 
> > > On 2020-09-14 21:41, Bjorn Andersson wrote:
> > > > On Tue 01 Sep 01:00 CDT 2020, Bao D. Nguyen wrote:
> > > >
> > > > > UFS's specifications supports a range of Vcc operating
> > > > > voltage levels. Add documentation for the UFS's Vcc voltage
> > > > > levels setting.
> > > > >
> > > > > Signed-off-by: Can Guo <cang@codeaurora.org>
> > > > > Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
> > > > > Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>
> > > > > ---
> > > > >  Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt | 2 ++
> > > > >  1 file changed, 2 insertions(+)
> > > > >
> > > > > diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> > > > > b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> > > > > index 415ccdd..7257b32 100644
> > > > > --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> > > > > +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> > > > > @@ -23,6 +23,8 @@ Optional properties:
> > > > >                            with "phys" attribute, provides phandle
> > > > > to UFS PHY node
> > > > >  - vdd-hba-supply        : phandle to UFS host controller supply
> > > > > regulator node
> > > > >  - vcc-supply            : phandle to VCC supply regulator node
> > > > > +- vcc-voltage-level     : specifies voltage levels for VCC supply.
> > > > > +                          Should be specified in pairs (min, max),
> > > > > units uV.
> > > >
> > > > What exactly are these pairs representing?
> > > The pair is the min and max Vcc voltage request to the PMIC chip.
> > > As a result, the regulator output voltage would only be in this range.
> > > 
> > 
> > If you have static min/max voltage constraints for a device on a
> > particular board the right way to handle this is to adjust the board's
> > regulator-min-microvolt and regulator-max-microvolt accordingly - and
> > not call regulator_set_voltage() from the river at all.
> > 
> > In other words, you shouldn't add this new property to describe
> > something already described in the node vcc-supply points to.
> > 
> > Regards,
> > Bjorn
> Thank you all for your comments. The current driver hardcoding 2.7V Vcc min
> voltage
> does not work for UFS3.0+ devices according to the UFS device JEDEC spec.
> However, we will
> try to address it in a different way.
> 

Right, but what I'm saying is that you should remove the
regulator_set_voltage() call from the driver and rely on the device's
dts, in which case you won't have this problem.

Thanks,
Bjorn

> Regards,
> Bao
> 
> > 
> > > >
> > > > Is this supposed to be 3 pairs of (min,max) for vcc, vcc and vccq2 to be
> > > > passed into a regulator_set_voltage() for each regulator?
> > > Yes, that's right. I should include the other power supplies in this
> > > change
> > > as well.
> > > >
> > > > Or are these some sort of "operating points" for the vcc-supply?
> > > >
> > > > Regards,
> > > > Bjorn
> > > >
> > > > >  - vccq-supply           : phandle to VCCQ supply regulator node
> > > > >  - vccq2-supply          : phandle to VCCQ2 supply regulator node
> > > > >  - vcc-supply-1p8        : For embedded UFS devices, valid VCC range
> > > > > is 1.7-1.95V
> > > > > --
> > > > > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> > > > > Forum,
> > > > > a Linux Foundation Collaborative Project
> > > > >

Re: [PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for UFS

[Rob Herring]

On Tue, Sep 15, 2020 at 2:10 AM <nguyenb@codeaurora.org> wrote:
>
> On 2020-09-14 11:35, Rob Herring wrote:
> > On Mon, Aug 31, 2020 at 11:00:47PM -0700, Bao D. Nguyen wrote:
> >> UFS's specifications supports a range of Vcc operating
> >> voltage levels. Add documentation for the UFS's Vcc voltage
> >> levels setting.
> >>
> >> Signed-off-by: Can Guo <cang@codeaurora.org>
> >> Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
> >> Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>
> >> ---
> >>  Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt | 2 ++
> >>  1 file changed, 2 insertions(+)
> >>
> >> diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> >> b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> >> index 415ccdd..7257b32 100644
> >> --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> >> +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> >> @@ -23,6 +23,8 @@ Optional properties:
> >>                            with "phys" attribute, provides phandle to
> >> UFS PHY node
> >>  - vdd-hba-supply        : phandle to UFS host controller supply
> >> regulator node
> >>  - vcc-supply            : phandle to VCC supply regulator node
> >> +- vcc-voltage-level     : specifies voltage levels for VCC supply.
> >> +                          Should be specified in pairs (min, max),
> >> units uV.
> >
> > The expectation is the regulator pointed to by 'vcc-supply' has the
> > voltage constraints. Those constraints are supposed to be the board
> > constraints, not the regulator operating design constraints. If that
> > doesn't work for your case, then it should be addressed in a common way
> > for the regulator binding.
> The UFS regulator has a min_uV and max_uV limits. Currently, the min and
> max are hardcoded
> to UFS2.1 Spec allowed values of 2.7V and 3.6V respectively.
> With this change, I am trying to fix a couple issues:
> 1. The 2.7V min value only applies to UFS2.1 devices. with UFS3.0+
> devices, the VCC min should be 2.4V.
> Hardcoding the min_uV to 2.7V does not work for UFS3.0+ devices.

Don't you know the device version attached and can adjust the voltage
based on that? Or you have to set the voltage first?

> 2. Allow users to select a different Vcc voltage within the allowed
> range.
> Using the min value, the UFS device is operating at marginal Vcc
> voltage.
> In addition the PMIC and the board designs may add some variables
> especially at extreme
> temperatures. We observe stability issues when using the min Vcc
> voltage.

Again, we have standard regulator properties for this already that you
can tune per board.

Rob

Re: [PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for UFS

[nguyenb]

On 2020-09-18 12:01, Rob Herring wrote:
> On Tue, Sep 15, 2020 at 2:10 AM <nguyenb@codeaurora.org> wrote:
>> 
>> On 2020-09-14 11:35, Rob Herring wrote:
>> > On Mon, Aug 31, 2020 at 11:00:47PM -0700, Bao D. Nguyen wrote:
>> >> UFS's specifications supports a range of Vcc operating
>> >> voltage levels. Add documentation for the UFS's Vcc voltage
>> >> levels setting.
>> >>
>> >> Signed-off-by: Can Guo <cang@codeaurora.org>
>> >> Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
>> >> Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>
>> >> ---
>> >>  Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt | 2 ++
>> >>  1 file changed, 2 insertions(+)
>> >>
>> >> diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> >> b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> >> index 415ccdd..7257b32 100644
>> >> --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> >> +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> >> @@ -23,6 +23,8 @@ Optional properties:
>> >>                            with "phys" attribute, provides phandle to
>> >> UFS PHY node
>> >>  - vdd-hba-supply        : phandle to UFS host controller supply
>> >> regulator node
>> >>  - vcc-supply            : phandle to VCC supply regulator node
>> >> +- vcc-voltage-level     : specifies voltage levels for VCC supply.
>> >> +                          Should be specified in pairs (min, max),
>> >> units uV.
>> >
>> > The expectation is the regulator pointed to by 'vcc-supply' has the
>> > voltage constraints. Those constraints are supposed to be the board
>> > constraints, not the regulator operating design constraints. If that
>> > doesn't work for your case, then it should be addressed in a common way
>> > for the regulator binding.
>> The UFS regulator has a min_uV and max_uV limits. Currently, the min 
>> and
>> max are hardcoded
>> to UFS2.1 Spec allowed values of 2.7V and 3.6V respectively.
>> With this change, I am trying to fix a couple issues:
>> 1. The 2.7V min value only applies to UFS2.1 devices. with UFS3.0+
>> devices, the VCC min should be 2.4V.
>> Hardcoding the min_uV to 2.7V does not work for UFS3.0+ devices.
> 
> Don't you know the device version attached and can adjust the voltage
> based on that? Or you have to set the voltage first?
Yes it is one of the solutions. Once detect the UFS device is version 
3.0+, you can lower
the voltage to 2.5V from the hardcoded value used by the driver. 
However, to change the
Vcc voltage, the host needs to follow a sequence to ensure safe 
operations after Vcc change
(device has to be in sleep mode, Vcc needs to go down to 0 then up to 
2.5V.)
Also same sequence is repeated for every host initialization which is 
inconvenient.

> 
>> 2. Allow users to select a different Vcc voltage within the allowed
>> range.
>> Using the min value, the UFS device is operating at marginal Vcc
>> voltage.
>> In addition the PMIC and the board designs may add some variables
>> especially at extreme
>> temperatures. We observe stability issues when using the min Vcc
>> voltage.
> 
> Again, we have standard regulator properties for this already that you
> can tune per board.
Thank you for the suggestion.

> 
> Rob

Re: [PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for UFS

[Bjorn Andersson]

On Mon 21 Sep 19:22 CDT 2020, nguyenb@codeaurora.org wrote:

> On 2020-09-18 12:01, Rob Herring wrote:
> > On Tue, Sep 15, 2020 at 2:10 AM <nguyenb@codeaurora.org> wrote:
> > > 
> > > On 2020-09-14 11:35, Rob Herring wrote:
> > > > On Mon, Aug 31, 2020 at 11:00:47PM -0700, Bao D. Nguyen wrote:
> > > >> UFS's specifications supports a range of Vcc operating
> > > >> voltage levels. Add documentation for the UFS's Vcc voltage
> > > >> levels setting.
> > > >>
> > > >> Signed-off-by: Can Guo <cang@codeaurora.org>
> > > >> Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
> > > >> Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>
> > > >> ---
> > > >>  Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt | 2 ++
> > > >>  1 file changed, 2 insertions(+)
> > > >>
> > > >> diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> > > >> b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> > > >> index 415ccdd..7257b32 100644
> > > >> --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> > > >> +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> > > >> @@ -23,6 +23,8 @@ Optional properties:
> > > >>                            with "phys" attribute, provides phandle to
> > > >> UFS PHY node
> > > >>  - vdd-hba-supply        : phandle to UFS host controller supply
> > > >> regulator node
> > > >>  - vcc-supply            : phandle to VCC supply regulator node
> > > >> +- vcc-voltage-level     : specifies voltage levels for VCC supply.
> > > >> +                          Should be specified in pairs (min, max),
> > > >> units uV.
> > > >
> > > > The expectation is the regulator pointed to by 'vcc-supply' has the
> > > > voltage constraints. Those constraints are supposed to be the board
> > > > constraints, not the regulator operating design constraints. If that
> > > > doesn't work for your case, then it should be addressed in a common way
> > > > for the regulator binding.
> > > The UFS regulator has a min_uV and max_uV limits. Currently, the min
> > > and
> > > max are hardcoded
> > > to UFS2.1 Spec allowed values of 2.7V and 3.6V respectively.
> > > With this change, I am trying to fix a couple issues:
> > > 1. The 2.7V min value only applies to UFS2.1 devices. with UFS3.0+
> > > devices, the VCC min should be 2.4V.
> > > Hardcoding the min_uV to 2.7V does not work for UFS3.0+ devices.
> > 
> > Don't you know the device version attached and can adjust the voltage
> > based on that? Or you have to set the voltage first?
> Yes it is one of the solutions. Once detect the UFS device is version 3.0+,
> you can lower
> the voltage to 2.5V from the hardcoded value used by the driver. However, to
> change the
> Vcc voltage, the host needs to follow a sequence to ensure safe operations
> after Vcc change
> (device has to be in sleep mode, Vcc needs to go down to 0 then up to 2.5V.)
> Also same sequence is repeated for every host initialization which is
> inconvenient.
> 

It sounds like you're suggesting that we detect the UFS device using
some voltage, then depending on version we might lower it to 2.5V.

I'm afraid I don't see any of this either documented or implemented in
these patches.

What is this initial detection voltage and how to you configure it?

Regards,
Bjorn

> > 
> > > 2. Allow users to select a different Vcc voltage within the allowed
> > > range.
> > > Using the min value, the UFS device is operating at marginal Vcc
> > > voltage.
> > > In addition the PMIC and the board designs may add some variables
> > > especially at extreme
> > > temperatures. We observe stability issues when using the min Vcc
> > > voltage.
> > 
> > Again, we have standard regulator properties for this already that you
> > can tune per board.
> Thank you for the suggestion.
> 
> > 
> > Rob

Re: [PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for UFS

[nguyenb]

On 2020-09-21 17:36, Bjorn Andersson wrote:
> On Mon 21 Sep 19:22 CDT 2020, nguyenb@codeaurora.org wrote:
> 
>> On 2020-09-18 12:01, Rob Herring wrote:
>> > On Tue, Sep 15, 2020 at 2:10 AM <nguyenb@codeaurora.org> wrote:
>> > >
>> > > On 2020-09-14 11:35, Rob Herring wrote:
>> > > > On Mon, Aug 31, 2020 at 11:00:47PM -0700, Bao D. Nguyen wrote:
>> > > >> UFS's specifications supports a range of Vcc operating
>> > > >> voltage levels. Add documentation for the UFS's Vcc voltage
>> > > >> levels setting.
>> > > >>
>> > > >> Signed-off-by: Can Guo <cang@codeaurora.org>
>> > > >> Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
>> > > >> Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>
>> > > >> ---
>> > > >>  Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt | 2 ++
>> > > >>  1 file changed, 2 insertions(+)
>> > > >>
>> > > >> diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> > > >> b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> > > >> index 415ccdd..7257b32 100644
>> > > >> --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> > > >> +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> > > >> @@ -23,6 +23,8 @@ Optional properties:
>> > > >>                            with "phys" attribute, provides phandle to
>> > > >> UFS PHY node
>> > > >>  - vdd-hba-supply        : phandle to UFS host controller supply
>> > > >> regulator node
>> > > >>  - vcc-supply            : phandle to VCC supply regulator node
>> > > >> +- vcc-voltage-level     : specifies voltage levels for VCC supply.
>> > > >> +                          Should be specified in pairs (min, max),
>> > > >> units uV.
>> > > >
>> > > > The expectation is the regulator pointed to by 'vcc-supply' has the
>> > > > voltage constraints. Those constraints are supposed to be the board
>> > > > constraints, not the regulator operating design constraints. If that
>> > > > doesn't work for your case, then it should be addressed in a common way
>> > > > for the regulator binding.
>> > > The UFS regulator has a min_uV and max_uV limits. Currently, the min
>> > > and
>> > > max are hardcoded
>> > > to UFS2.1 Spec allowed values of 2.7V and 3.6V respectively.
>> > > With this change, I am trying to fix a couple issues:
>> > > 1. The 2.7V min value only applies to UFS2.1 devices. with UFS3.0+
>> > > devices, the VCC min should be 2.4V.
>> > > Hardcoding the min_uV to 2.7V does not work for UFS3.0+ devices.
>> >
>> > Don't you know the device version attached and can adjust the voltage
>> > based on that? Or you have to set the voltage first?
>> Yes it is one of the solutions. Once detect the UFS device is version 
>> 3.0+,
>> you can lower
>> the voltage to 2.5V from the hardcoded value used by the driver. 
>> However, to
>> change the
>> Vcc voltage, the host needs to follow a sequence to ensure safe 
>> operations
>> after Vcc change
>> (device has to be in sleep mode, Vcc needs to go down to 0 then up to 
>> 2.5V.)
>> Also same sequence is repeated for every host initialization which is
>> inconvenient.
>> 
> 
> It sounds like you're suggesting that we detect the UFS device using
> some voltage, then depending on version we might lower it to 2.5V.
Yes, that is one possible solution.

> I'm afraid I don't see any of this either documented or implemented in
> these patches.
I was responding to a comment about detecting the device version and 
change the voltage
based on the detection. It is not implemented in this patch. Maybe I 
should stop
discussing another possible solution, even though related to the topic, 
it is not
implemented in this patch.

> 
> What is this initial detection voltage and how to you configure it?
The initial voltage would be 2.9V and is lowered to 2.5V if UFS3.0+ 
device is detected.
We would call the regulator_set_voltage() to set to a specific voltage 
level.

Regards,
Bao

> 
> Regards,
> Bjorn
> 
>> >
>> > > 2. Allow users to select a different Vcc voltage within the allowed
>> > > range.
>> > > Using the min value, the UFS device is operating at marginal Vcc
>> > > voltage.
>> > > In addition the PMIC and the board designs may add some variables
>> > > especially at extreme
>> > > temperatures. We observe stability issues when using the min Vcc
>> > > voltage.
>> >
>> > Again, we have standard regulator properties for this already that you
>> > can tune per board.
>> Thank you for the suggestion.
>> 
>> >
>> > Rob