linux-kernel - Re: [PATCH v2 3/7] regulator: qcom-labibb: Implement pull-down, softstart, active discharge

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Date:   Sun, 17 Jan 2021 19:15:58 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     linux-arm-msm@...r.kernel.org, agross@...nel.org,
        lgirdwood@...il.com, broonie@...nel.org, robh+dt@...nel.org,
        sumit.semwal@...aro.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, phone-devel@...r.kernel.org,
        konrad.dybcio@...ainline.org, marijn.suijten@...ainline.org,
        martin.botka@...ainline.org
Subject: Re: [PATCH v2 3/7] regulator: qcom-labibb: Implement pull-down,
 softstart, active discharge

Il 15/01/21 05:53, Bjorn Andersson ha scritto:
> On Wed 13 Jan 13:42 CST 2021, AngeloGioacchino Del Regno wrote:
> 
>> Soft start is required to avoid inrush current during LAB ramp-up and
>> IBB ramp-down, protecting connected hardware to which we supply voltage.
>>
>> Since soft start is configurable on both LAB and IBB regulators, it
>> was necessary to add two DT properties, respectively "qcom,soft-start-us"
>> to control LAB ramp-up and "qcom,discharge-resistor-kohms" to control
>> the discharge resistor for IBB ramp-down, which obviously brought the
>> need of implementing a of_parse callback for both regulators.
>>
>> Finally, also implement pull-down mode in order to avoid unpredictable
>> behavior when the regulators are disabled (random voltage spikes etc).
>>
>> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...ainline.org>
>> ---
>>   drivers/regulator/qcom-labibb-regulator.c | 94 +++++++++++++++++++++++
>>   1 file changed, 94 insertions(+)
>>
>> diff --git a/drivers/regulator/qcom-labibb-regulator.c b/drivers/regulator/qcom-labibb-regulator.c
>> index d364f54ad294..38ab1eba1c59 100644
>> --- a/drivers/regulator/qcom-labibb-regulator.c
>> +++ b/drivers/regulator/qcom-labibb-regulator.c
>> @@ -29,12 +29,23 @@
>>   #define LABIBB_STATUS1_VREG_OK_BIT	BIT(7)
>>   #define LABIBB_CONTROL_ENABLE		BIT(7)
>>   
>> +#define REG_LABIBB_PD_CTL		0x47
>> + #define LAB_PD_CTL_MASK		GENMASK(1, 0)
>> + #define IBB_PD_CTL_MASK		(BIT(0) | BIT(7))
>> + #define LAB_PD_CTL_STRONG_PULL		BIT(0)
>> + #define IBB_PD_CTL_HALF_STRENGTH	BIT(0)
>> + #define IBB_PD_CTL_EN			BIT(7)
>> +
>>   #define REG_LABIBB_CURRENT_LIMIT	0x4b
>>    #define LAB_CURRENT_LIMIT_MASK		GENMASK(2, 0)
>>    #define IBB_CURRENT_LIMIT_MASK		GENMASK(4, 0)
>>    #define LAB_CURRENT_LIMIT_OVERRIDE_EN	BIT(3)
>>    #define LABIBB_CURRENT_LIMIT_EN	BIT(7)
>>   
>> +#define REG_IBB_PWRUP_PWRDN_CTL_1	0x58
>> + #define IBB_CTL_1_DISCHARGE_EN		BIT(2)
>> +
>> +#define REG_LABIBB_SOFT_START_CTL	0x5f
>>   #define REG_LABIBB_SEC_ACCESS		0xd0
>>    #define LABIBB_SEC_UNLOCK_CODE		0xa5
>>   
>> @@ -60,6 +71,8 @@ struct labibb_regulator {
>>   	struct labibb_current_limits	uA_limits;
>>   	u16				base;
>>   	u8				type;
>> +	u8				dischg_sel;
>> +	u8				soft_start_sel;
>>   };
>>   
>>   struct labibb_regulator_data {
>> @@ -120,6 +133,70 @@ static int qcom_labibb_get_current_limit(struct regulator_dev *rdev)
>>   	return (cur_step * lim->uA_step) + lim->uA_min;
>>   }
>>   
>> +static int qcom_labibb_set_soft_start(struct regulator_dev *rdev)
>> +{
>> +	struct labibb_regulator *vreg = rdev_get_drvdata(rdev);
>> +	u32 val = 0;
>> +
>> +	if (vreg->type == QCOM_IBB_TYPE)
>> +		val = vreg->dischg_sel;
>> +	else
>> +		val = vreg->soft_start_sel;
>> +
>> +	return regmap_write(rdev->regmap, rdev->desc->soft_start_reg, val);
>> +}
>> +
>> +static int qcom_labibb_get_table_sel(const int *table, int sz, u32 value)
>> +{
>> +	int i;
>> +
>> +	for (i = 0; i < sz; i++)
>> +		if (table[i] == value)
>> +			return i;
>> +	return -EINVAL;
>> +}
>> +
>> +/* IBB discharge resistor values in KOhms */
>> +static const int dischg_resistor_values[] = { 300, 64, 32, 16 };
>> +
>> +/* Soft start time in microseconds */
>> +static const int soft_start_values[] = { 200, 400, 600, 800 };
>> +
>> +static int qcom_labibb_of_parse_cb(struct device_node *np,
>> +				   const struct regulator_desc *desc,
>> +				   struct regulator_config *config)
>> +{
>> +	struct labibb_regulator *vreg = config->driver_data;
>> +	u32 dischg_kohms, soft_start_time;
>> +	int ret;
>> +
>> +	ret = of_property_read_u32(np, "qcom,discharge-resistor-kohms",
>> +				       &dischg_kohms);
>> +	if (ret)
>> +		dischg_kohms = 300;
> 
> Nit, if you just initialize dischg_kohms to 300 during definition you
> can rely on of_property_read_u32() not updating the value on failure...
> 

I can change it if that's really necessary, I did it like this in an
attempt of spoon-feed the logic to the reader, but perhaps just
initializing it during definition would achieve the same, anyway.

Should I?

> That said, I think this patch looks good.
> 
> Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> 

Thank you!

> Regards,
> Bjorn
>