2020-01-23 07:27:22

by Can Guo

Subject: [PATCH v4 2/8] scsi: ufs: set load before setting voltage in regulators

From: Asutosh Das <[email protected]>

This sequence change is required to avoid dips in voltage
during boot-up.

Apparently, this dip is caused because in the original
sequence, the regulators are initialized in lpm mode.
And then when the load is set to high, and more current
is drawn, than is allowed in lpm, the dip is seen.

Signed-off-by: Asutosh Das <[email protected]>
Signed-off-by: Can Guo <[email protected]>
---
drivers/scsi/ufs/ufshcd.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index c2de29f..c386c2d 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -7225,6 +7225,11 @@ static int ufshcd_config_vreg(struct device *dev,
name = vreg->name;

if (regulator_count_voltages(reg) > 0) {
+ uA_load = on ? vreg->max_uA : 0;
+ ret = ufshcd_config_vreg_load(dev, vreg, uA_load);
+ if (ret)
+ goto out;
+
if (vreg->min_uV && vreg->max_uV) {
min_uV = on ? vreg->min_uV : 0;
ret = regulator_set_voltage(reg, min_uV, vreg->max_uV);
@@ -7235,11 +7240,6 @@ static int ufshcd_config_vreg(struct device *dev,
goto out;
}
}
-
- uA_load = on ? vreg->max_uA : 0;
- ret = ufshcd_config_vreg_load(dev, vreg, uA_load);
- if (ret)
- goto out;
}
out:
return ret;
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

2020-01-23 07:51:18

by hongwus

Subject: Re: [PATCH v4 2/8] scsi: ufs: set load before setting voltage in regulators

Hi Can,
It makes sense that set the load before enable regulator or set
voltage. Just avoid voltage drop.

On 2020-01-23 15:25, Can Guo wrote:
> From: Asutosh Das <[email protected]>
>
> This sequence change is required to avoid dips in voltage
> during boot-up.
>
> Apparently, this dip is caused because in the original
> sequence, the regulators are initialized in lpm mode.
> And then when the load is set to high, and more current
> is drawn, than is allowed in lpm, the dip is seen.
>
> Signed-off-by: Asutosh Das <[email protected]>
> Signed-off-by: Can Guo <[email protected]>
> ---
> drivers/scsi/ufs/ufshcd.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index c2de29f..c386c2d 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -7225,6 +7225,11 @@ static int ufshcd_config_vreg(struct device
> *dev,
> name = vreg->name;
>
> if (regulator_count_voltages(reg) > 0) {
> + uA_load = on ? vreg->max_uA : 0;
> + ret = ufshcd_config_vreg_load(dev, vreg, uA_load);
> + if (ret)
> + goto out;
> +
> if (vreg->min_uV && vreg->max_uV) {
> min_uV = on ? vreg->min_uV : 0;
> ret = regulator_set_voltage(reg, min_uV, vreg->max_uV);
> @@ -7235,11 +7240,6 @@ static int ufshcd_config_vreg(struct device
> *dev,
> goto out;
> }
> }
> -
> - uA_load = on ? vreg->max_uA : 0;
> - ret = ufshcd_config_vreg_load(dev, vreg, uA_load);
> - if (ret)
> - goto out;
> }
> out:
> return ret;


Reviewed-by: Hongwu Su <[email protected]>