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 13:44:11 +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 31.01.2023 10:28, Devi Priya wrote:
> 
> 
> 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.
Okay, I didn't quite catch that there's *only* an i2c PMIC on this
platform.. Looking at the MP5496 datasheet though, reading back
the voltage should be possible via simply reading the fields that
are used to set it.

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
> Best Regards,
> Devi Priya