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

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Message-ID: <cc037133-7c45-325f-4a1d-9855d033ae5c@linaro.org>
Date:   Fri, 27 Jan 2023 17:10:01 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Devi Priya <quic_devipriy@...cinc.com>, 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 27.01.2023 17:07, Devi Priya wrote:
> 
> 
> 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
Unless something changed, RPM regulator framework is simply a
fancy front-end for communicating with the PMIC over SPMI, AFAIK..

Konrad
> 
>>>   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