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

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Date:   Tue, 31 Jan 2023 14:58:39 +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 1/27/2023 9:40 PM, Konrad Dybcio wrote:
> 
> 
> 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
Currently in our driver, the voltage write request will be sent to RPM 
via GLINK which then writes it to the PMIC over I2C using the below APIs
qcom_rpm_smd_write -> rpmsg_send
In IPQ9574, we do not have SPMI support or the support to readback voltage.

>>
>>>>    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
Best Regards,
Devi Priya