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

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Date:   Fri, 27 Jan 2023 21:37:42 +0530
From:   Devi Priya <quic_devipriy@...cinc.com>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>, <agross@...nel.org>,
        <andersson@...nel.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>, <quic_ipkumar@...cinc.com>
Subject: Re: [PATCH 6/6] regulator: qcom_smd: Add support to define the bootup
 voltage



On 1/13/2023 9:07 PM, Konrad Dybcio wrote:
> 
> 
> On 13.01.2023 16:03, 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>
>> ---
> Or maybe hook it up to the spmi_regulator_common_get_voltage()
> from the SPMI regulator driver and read the real voltage instead
> of relying on hardcoded values thay may differ between boards?
> 
> Konrad
In IPQ9574, SPMI regulator is not used. We are using RPM-Glink 
communication and the regulators are controlled by RPM.
In this case, we don't have an option to readback the bootup voltage and 
so, we have hardcoded the values

>>   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 },
>>   	{}
>>   };
>>   
>> @@ -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