Re: [PATCH v3 2/3] pmdomain: mediatek: Add support for secure modem power domain control

On 20/07/2026 22:46, Nikolai Burov via B4 Relay wrote:
> From: Nikolai Burov <[email protected]>
> 
> On recent MediaTek SoCs such as MT6858, the kernel is required to use
> a secure monitor call (SMC) to enable or disable the modem power domain.
> The power domain control register can be read, but firmware prevents it
> from being modified directly. Some other parts of the power sequence,
> such as setting the ext_buck_iso register, still need to be performed on
> the kernel side.
> 
> In preparation for modem support, add a flag to enable this new power
> sequence for SoCs that need it. Power domains using this flag are not
> expected to configure any bus protection registers, since these are
> handled internally by the SMC call.
> 
> Signed-off-by: Nikolai Burov <[email protected]>

Reviewed-by: Matthias Brugger <[email protected]>

> ---
>   drivers/pmdomain/mediatek/mtk-pm-domains.c | 50 +++++++++++++++++++++++++++---
>   drivers/pmdomain/mediatek/mtk-pm-domains.h |  1 +
>   include/linux/soc/mediatek/mtk_sip_svc.h   |  3 ++
>   3 files changed, 49 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pmdomain/mediatek/mtk-pm-domains.c b/drivers/pmdomain/mediatek/mtk-pm-domains.c
> index 8309a4b46afb..5b4d860318a4 100644
> --- a/drivers/pmdomain/mediatek/mtk-pm-domains.c
> +++ b/drivers/pmdomain/mediatek/mtk-pm-domains.c
> @@ -57,6 +57,10 @@
>   
>   #define MTK_SIP_KERNEL_HWCCF_CONTROL	MTK_SIP_SMC_CMD(0x540)
>   
> +/* Secure MTCMOS commands for modem subsystem */
> +#define MTK_MD_MTCMOS_ENABLE		18
> +#define MTK_MD_MTCMOS_DISABLE		19
> +
>   struct scpsys_domain {
>   	struct generic_pm_domain genpd;
>   	const struct scpsys_domain_data *data;
> @@ -668,6 +672,34 @@ static int scpsys_modem_pwrseq_off(struct scpsys_domain *pd)
>   	return 0;
>   }
>   
> +static bool scpsys_modem_sec_poll(unsigned long cmd)
> +{
> +	struct arm_smccc_res res;
> +
> +	arm_smccc_smc(MTK_SIP_KERNEL_CCCI_CONTROL, cmd, 1, 0, 0, 0, 0, 0, &res);
> +
> +	return res.a0 == 0;
> +}
> +
> +static int scpsys_modem_sec_power_on(bool on)
> +{
> +	struct arm_smccc_res res;
> +	unsigned long cmd = on ? MTK_MD_MTCMOS_ENABLE : MTK_MD_MTCMOS_DISABLE;
> +	bool tmp;
> +	int ret;
> +
> +	arm_smccc_smc(MTK_SIP_KERNEL_CCCI_CONTROL, cmd, 0, 0, 0, 0, 0, 0, &res);
> +	if (res.a0 == 0)
> +		return 0;
> +
> +	ret = readx_poll_timeout(scpsys_modem_sec_poll, cmd, tmp, tmp,
> +				 MTK_POLL_DELAY_US, MTK_POLL_TIMEOUT);
> +	if (ret < 0)
> +		return ret;
> +
> +	return 0;
> +}
> +
>   static int scpsys_power_on(struct generic_pm_domain *genpd)
>   {
>   	struct scpsys_domain *pd = container_of(genpd, struct scpsys_domain, genpd);
> @@ -686,7 +718,9 @@ static int scpsys_power_on(struct generic_pm_domain *genpd)
>   		regmap_clear_bits(scpsys->base, pd->data->ext_buck_iso_offs,
>   				  pd->data->ext_buck_iso_mask);
>   
> -	if (MTK_SCPD_CAPS(pd, MTK_SCPD_MODEM_PWRSEQ))
> +	if (MTK_SCPD_CAPS(pd, MTK_SCPD_MODEM_SECURE_PWRSEQ))
> +		ret = scpsys_modem_sec_power_on(true);
> +	else if (MTK_SCPD_CAPS(pd, MTK_SCPD_MODEM_PWRSEQ))
>   		ret = scpsys_modem_pwrseq_on(pd);
>   	else if (MTK_SCPD_CAPS(pd, MTK_SCPD_SIMPLE_PWRSEQ))
>   		ret = scpsys_simple_pwrseq_on(pd);
> @@ -717,7 +751,8 @@ static int scpsys_power_on(struct generic_pm_domain *genpd)
>   			goto err_pwr_ack;
>   	}
>   
> -	if (!MTK_SCPD_CAPS(pd, MTK_SCPD_SIMPLE_PWRSEQ)) {
> +	if (!MTK_SCPD_CAPS(pd, MTK_SCPD_SIMPLE_PWRSEQ) &&
> +	    !MTK_SCPD_CAPS(pd, MTK_SCPD_MODEM_SECURE_PWRSEQ)) {
>   		ret = scpsys_sram_enable(pd);
>   		if (ret < 0)
>   			goto err_disable_subsys_clks;
> @@ -739,7 +774,8 @@ static int scpsys_power_on(struct generic_pm_domain *genpd)
>   err_enable_bus_protect:
>   	scpsys_bus_protect_enable(pd, 0);
>   err_disable_sram:
> -	if (!MTK_SCPD_CAPS(pd, MTK_SCPD_SIMPLE_PWRSEQ))
> +	if (!MTK_SCPD_CAPS(pd, MTK_SCPD_SIMPLE_PWRSEQ) &&
> +	    !MTK_SCPD_CAPS(pd, MTK_SCPD_MODEM_SECURE_PWRSEQ))
>   		scpsys_sram_disable(pd);
>   err_disable_subsys_clks:
>   	if (!MTK_SCPD_CAPS(pd, MTK_SCPD_STRICT_BUS_PROTECTION))
> @@ -761,7 +797,11 @@ static int scpsys_power_off_internal(struct scpsys_domain *pd)
>   	if (ret < 0)
>   		return ret;
>   
> -	if (!MTK_SCPD_CAPS(pd, MTK_SCPD_SIMPLE_PWRSEQ)) {
> +	if (MTK_SCPD_CAPS(pd, MTK_SCPD_MODEM_SECURE_PWRSEQ)) {
> +		ret = scpsys_modem_sec_power_on(false);
> +		if (ret)
> +			return ret;
> +	} else if (!MTK_SCPD_CAPS(pd, MTK_SCPD_SIMPLE_PWRSEQ)) {
>   		ret = scpsys_sram_disable(pd);
>   		if (ret < 0)
>   			return ret;
> @@ -781,7 +821,7 @@ static int scpsys_power_off_internal(struct scpsys_domain *pd)
>   		ret = scpsys_modem_pwrseq_off(pd);
>   	else if (MTK_SCPD_CAPS(pd, MTK_SCPD_SIMPLE_PWRSEQ))
>   		ret = scpsys_simple_pwrseq_off(pd);
> -	else
> +	else if (!MTK_SCPD_CAPS(pd, MTK_SCPD_MODEM_SECURE_PWRSEQ))
>   		ret = scpsys_ctl_pwrseq_off(pd);
>   
>   	if (ret < 0) {
> diff --git a/drivers/pmdomain/mediatek/mtk-pm-domains.h b/drivers/pmdomain/mediatek/mtk-pm-domains.h
> index 092403de66fa..8690690335ad 100644
> --- a/drivers/pmdomain/mediatek/mtk-pm-domains.h
> +++ b/drivers/pmdomain/mediatek/mtk-pm-domains.h
> @@ -18,6 +18,7 @@
>   #define MTK_SCPD_SKIP_RESET_B		BIT(11)
>   #define MTK_SCPD_INFRA_PWR_CTL		BIT(12)
>   #define MTK_SCPD_SIMPLE_PWRSEQ		BIT(13)
> +#define MTK_SCPD_MODEM_SECURE_PWRSEQ	BIT(14)
>   #define MTK_SCPD_CAPS(_scpd, _x)	((_scpd)->data ?		\
>   					 (_scpd)->data->caps & (_x) :	\
>   					 (_scpd)->hwv_data->caps & (_x))
> diff --git a/include/linux/soc/mediatek/mtk_sip_svc.h b/include/linux/soc/mediatek/mtk_sip_svc.h
> index abe24a73ee19..6c95a29b79fa 100644
> --- a/include/linux/soc/mediatek/mtk_sip_svc.h
> +++ b/include/linux/soc/mediatek/mtk_sip_svc.h
> @@ -22,6 +22,9 @@
>   	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, MTK_SIP_SMC_CONVENTION, \
>   			   ARM_SMCCC_OWNER_SIP, fn_id)
>   
> +/* Modem related SMC call */
> +#define MTK_SIP_KERNEL_CCCI_CONTROL	MTK_SIP_SMC_CMD(0x505)
> +
>   /* DVFSRC SMC calls */
>   #define MTK_SIP_DVFSRC_VCOREFS_CONTROL	MTK_SIP_SMC_CMD(0x506)
>   
>