linux-kernel - Re: [PATCH 6/6] regulator: qcom_smd: Add support to define the bootup voltage

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Date:   Thu, 2 Feb 2023 16:39:56 +0530
From:   Devi Priya <quic_devipriy@...cinc.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        <agross@...nel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>, <lgirdwood@...il.com>,
        <broonie@...nel.org>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <devicetree@...r.kernel.org>
CC:     <quic_srichara@...cinc.com>, <quic_gokulsri@...cinc.com>,
        <quic_sjaganat@...cinc.com>, <quic_kathirav@...cinc.com>,
        <quic_arajkuma@...cinc.com>, <quic_anusha@...cinc.com>,
        <quic_poovendh@...cinc.com>
Subject: Re: [PATCH 6/6] regulator: qcom_smd: Add support to define the bootup
 voltage



On 1/31/2023 3:07 PM, Dmitry Baryshkov wrote:
> On 13/01/2023 17:03, devi priya wrote:
>> Kernel does not know the initial voltage set by the bootloaders.
>> During regulator registration, the voltage variable is just declared
>> and it is zero. Based on that, the regulator framework considers current
>> the voltage as zero and tries to bring up each regulator to minimum
>> the supported voltage.
>>
>> This introduces a dip in the voltage during kernel boot and gets
>> stabilized once the voltage scaling comes into picture.
>>
>> To avoid the voltage dip, adding support to define the
>> bootup voltage set by the boodloaders and based on it, regulator
>> framework understands that proper voltage is already set
>>
>> Co-developed-by: Praveenkumar I <quic_ipkumar@...cinc.com>
>> Signed-off-by: Praveenkumar I <quic_ipkumar@...cinc.com>
>> Signed-off-by: devi priya <quic_devipriy@...cinc.com>
>> ---
>>   drivers/regulator/qcom_smd-regulator.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/regulator/qcom_smd-regulator.c 
>> b/drivers/regulator/qcom_smd-regulator.c
>> index 1eb17d378897..49a36b07397c 100644
>> --- a/drivers/regulator/qcom_smd-regulator.c
>> +++ b/drivers/regulator/qcom_smd-regulator.c
>> @@ -800,6 +800,7 @@ struct rpm_regulator_data {
>>       u32 id;
>>       const struct regulator_desc *desc;
>>       const char *supply;
>> +    int boot_uV; /* To store the bootup voltage set by bootloaders */
>>   };
>>   static const struct rpm_regulator_data rpm_mp5496_regulators[] = {
>> @@ -809,7 +810,7 @@ static const struct rpm_regulator_data 
>> rpm_mp5496_regulators[] = {
>>   };
>>   static const struct rpm_regulator_data 
>> rpm_ipq9574_mp5496_regulators[] = {
>> -    { "s1", QCOM_SMD_RPM_SMPA, 1, &ipq9574_mp5496_smpa1, "s1" },
>> +    { "s1", QCOM_SMD_RPM_SMPA, 1, &ipq9574_mp5496_smpa1, "s1", 875000 },
> 
> I think this is a peculiarity of the particular board that than a 
> property of the PMIC. Please describe this in the board or SoC DTS if 
> the value can not be read using the software .
> 
The bootup voltage is actually blown into the OTP register of the PMIC 
and so, it remains the same across boards for IPQ9574 SoC
>>       {}
>>   };
>> @@ -1394,6 +1395,9 @@ static int rpm_regulator_init_vreg(struct 
>> qcom_rpm_reg *vreg, struct device *dev
>>       vreg->type    = rpm_data->type;
>>       vreg->id    = rpm_data->id;
>> +    if (rpm_data->boot_uV)
>> +        vreg->uV = rpm_data->boot_uV;
>> +
>>       memcpy(&vreg->desc, rpm_data->desc, sizeof(vreg->desc));
>>       vreg->desc.name = rpm_data->name;
>>       vreg->desc.supply_name = rpm_data->supply;
> 
Best Regards,
Devi Priya