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

[Matthias Brugger]

On 14/07/2026 15:43, Nikolai Burov via B4 Relay wrote:
> From: Nikolai Burov <nikolai.burov@xxxxxxxxx>
>
> 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. 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.
>
> Signed-off-by: Nikolai Burov <nikolai.burov@xxxxxxxxx>
> ---
>   drivers/pmdomain/mediatek/mtk-pm-domains.c | 54 +++++++++++++++++++++++++++---
>   drivers/pmdomain/mediatek/mtk-pm-domains.h |  1 +
>   include/linux/soc/mediatek/mtk_sip_svc.h   |  3 ++
>   3 files changed, 53 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/pmdomain/mediatek/mtk-pm-domains.c b/drivers/pmdomain/mediatek/mtk-pm-domains.c
> index e1cfd4223473..56437b32b252 100644
> --- a/drivers/pmdomain/mediatek/mtk-pm-domains.c
> +++ b/drivers/pmdomain/mediatek/mtk-pm-domains.c
> @@ -57,6 +57,12 @@
>   
>   #define MTK_SIP_KERNEL_HWCCF_CONTROL	MTK_SIP_SMC_CMD(0x540)
>   
> +/* Power domain commands for MTK_SIP_KERNEL_CCCI_CONTROL */
> +enum {
> +	MTK_MD_MTCMOS_ENABLE = 18,
> +	MTK_MD_MTCMOS_DISABLE = 19,
> +};
> +
>   struct scpsys_domain {
>   	struct generic_pm_domain genpd;
>   	const struct scpsys_domain_data *data;
> @@ -615,6 +621,34 @@ static void scpsys_modem_pwrseq_off(struct scpsys_domain *pd)
>   		regmap_clear_bits(scpsys->base, pd->data->ctl_offs, PWR_RST_B_BIT);
>   }
>   
> +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);
> @@ -633,7 +667,9 @@ 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))
> +		ret = scpsys_modem_sec_power_on(true);
> +	else if (MTK_SCPD_CAPS(pd, MTK_SCPD_MODEM_PWRSEQ))
>   		ret = scpsys_modem_pwrseq_on(pd);

So we can have either cap MTK_SCPD_MODEM_SECURE or MTK_SCPD_MODEM_PWRSEQ but...

[...]

> @@ -719,10 +761,12 @@ static int scpsys_power_off(struct generic_pm_domain *genpd)
>   	if (ret < 0)
>   		return ret;
>   
> -	if (MTK_SCPD_CAPS(pd, MTK_SCPD_MODEM_PWRSEQ))
> -		scpsys_modem_pwrseq_off(pd);
> -	else
> -		scpsys_ctl_pwrseq_off(pd);
> +	if (!MTK_SCPD_CAPS(pd, MTK_SCPD_MODEM_SECURE)) {
> +		if (MTK_SCPD_CAPS(pd, MTK_SCPD_MODEM_PWRSEQ))

... here it seems that a power domain could have both caps set. I suppose this 
second case does not exist, but code should treat just one of the two cases 
(mutual exclusive or not mutual exclusive).

Regards,
Matthias