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

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Message-ID: <3813f262-8d36-2b1c-2230-cbb5a161d4c1@linaro.org>
Date:   Tue, 31 Jan 2023 11:37:35 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     devi priya <quic_devipriy@...cinc.com>, 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 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 .

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

-- 
With best wishes
Dmitry