Re: [PATCH v7 09/10] pmdomain: samsung: implement SMC to save / restore TZ config

[Peter Griffin]

On Fri, 6 Mar 2026 at 10:30, André Draszik <andre.draszik@xxxxxxxxxx> wrote:
>
> Newer Exynos platforms have a Distributed Trust Zone Protection Control
> (DTZPC) linked to each power domain. It controls the access permissions
> to various registers from secure and non-secure world. An SMC call is
> required to instruct the firmware that the power domain is about to be
> turned off and again once it was turned on. This allows the firmware to
> save and restore the DTZPC configuration. Without, register access to
> various registers becomes impossible from Linux (causing SError), as
> the PoR configuration doesn't allow access.
>
> Neither the requirement for the SMC call, nor its arguments appear to
> be specific to gs101, as at least Exynos E850 also uses the same as can
> be seen in [1], hence prefix the new macros simply with EXYNOS_.
>
> At least on gs101, this SMC call isn't implemented for all power
> domains (e.g. it's missing for HSI2 (UFS)), therefore we issue a test
> SMC to store the configuration during probe, and if it fails we mark a
> domain as always-on to avoid the SErrors and to avoid unnecessarily
> retrying for each domain on/off.
>
> Link: https://lore.kernel.org/all/20230308233822.31180-4-semen.protsenko@xxxxxxxxxx/ [1]
> Signed-off-by: André Draszik <andre.draszik@xxxxxxxxxx>
> ---

Reviewed-by: Peter Griffin <peter.griffin@xxxxxxxxxx>

>  drivers/pmdomain/samsung/exynos-pm-domains.c | 96 ++++++++++++++++++++++++++--
>  1 file changed, 90 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/pmdomain/samsung/exynos-pm-domains.c b/drivers/pmdomain/samsung/exynos-pm-domains.c
> index 41a232b3cdaf..f59986b56213 100644
> --- a/drivers/pmdomain/samsung/exynos-pm-domains.c
> +++ b/drivers/pmdomain/samsung/exynos-pm-domains.c
> @@ -9,6 +9,7 @@
>  // conjunction with runtime-pm. Support for both device-tree and non-device-tree
>  // based power domain support is included.
>
> +#include <linux/arm-smccc.h>
>  #include <linux/err.h>
>  #include <linux/platform_device.h>
>  #include <linux/slab.h>
> @@ -16,12 +17,19 @@
>  #include <linux/pm_domain.h>
>  #include <linux/delay.h>
>  #include <linux/of.h>
> +#include <linux/of_address.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/regmap.h>
>
> +#define EXYNOS_SMC_CMD_PREPARE_PD_ONOFF                0x82000410
> +#define EXYNOS_GET_IN_PD_DOWN                  0
> +#define EXYNOS_WAKEUP_PD_DOWN                  1
> +#define EXYNOS_RUNTIME_PM_TZPC_GROUP           2
> +
>  struct exynos_pm_domain_config {
>         /* Value for LOCAL_PWR_CFG and STATUS fields for each domain */
>         u32 local_pwr_cfg;
> +       u32 smc_offset;
>         bool use_parent_regmap;
>  };
>
> @@ -32,11 +40,28 @@ struct exynos_pm_domain {
>         struct regmap *regmap;
>         struct device *dev;
>         struct generic_pm_domain pd;
> -       u32 local_pwr_cfg;
> +       const struct exynos_pm_domain_config *cfg;
>         u32 configuration_reg;
>         u32 status_reg;
> +       phys_addr_t ac_pa;
>  };
>
> +static int exynos_pd_access_controller_power(struct exynos_pm_domain *pd,
> +                                            bool power_on)
> +{
> +       struct arm_smccc_res res;
> +
> +       if (!pd->ac_pa || !pd->cfg->smc_offset)
> +               return 0;
> +
> +       arm_smccc_smc(EXYNOS_SMC_CMD_PREPARE_PD_ONOFF,
> +                     power_on ? EXYNOS_WAKEUP_PD_DOWN : EXYNOS_GET_IN_PD_DOWN,
> +                     pd->ac_pa + pd->cfg->smc_offset,
> +                     EXYNOS_RUNTIME_PM_TZPC_GROUP, 0, 0, 0, 0, &res);
> +
> +       return res.a0;
> +}
> +
>  static int exynos_pd_power(struct generic_pm_domain *domain, bool power_on)
>  {
>         struct exynos_pm_domain *pd;
> @@ -45,7 +70,17 @@ static int exynos_pd_power(struct generic_pm_domain *domain, bool power_on)
>
>         pd = container_of(domain, struct exynos_pm_domain, pd);
>
> -       pwr = power_on ? pd->local_pwr_cfg : 0;
> +       if (!power_on) {
> +               err = exynos_pd_access_controller_power(pd, power_on);
> +               if (err) {
> +                       dev_err(pd->dev,
> +                               "SMC for power domain %s %sable failed: %d\n",
> +                               domain->name, power_on ? "en" : "dis", err);
> +                       return err;
> +               }
> +       }
> +
> +       pwr = power_on ? pd->cfg->local_pwr_cfg : 0;
>         err = regmap_write(pd->regmap, pd->configuration_reg, pwr);
>         if (err) {
>                 dev_err(pd->dev,
> @@ -60,7 +95,7 @@ static int exynos_pd_power(struct generic_pm_domain *domain, bool power_on)
>                 unsigned int val;
>
>                 err = regmap_read(pd->regmap, pd->status_reg, &val);
> -               if (err || ((val & pd->local_pwr_cfg) != pwr)) {
> +               if (err || ((val & pd->cfg->local_pwr_cfg) != pwr)) {
>                         cpu_relax();
>                         usleep_range(80, 100);
>                         continue;
> @@ -72,9 +107,21 @@ static int exynos_pd_power(struct generic_pm_domain *domain, bool power_on)
>         if (!timeout && !err)
>                 /* Only return timeout if no other error also occurred. */
>                 err = -ETIMEDOUT;
> -       if (err)
> +       if (err) {
>                 dev_err(pd->dev, "Power domain %s %sable failed: %d\n",
>                         domain->name, power_on ? "en" : "dis", err);
> +               return err;
> +       }
> +
> +       if (power_on) {
> +               err = exynos_pd_access_controller_power(pd, power_on);
> +               if (err) {
> +                       dev_err(pd->dev,
> +                               "SMC for power domain %s %sable failed: %d\n",
> +                               domain->name, power_on ? "en" : "dis", err);
> +                       return err;
> +               }
> +       }
>
>         return err;
>  }
> @@ -99,6 +146,7 @@ static const struct exynos_pm_domain_config exynos5433_cfg = {
>
>  static const struct exynos_pm_domain_config gs101_cfg = {
>         .local_pwr_cfg          = BIT(0),
> +       .smc_offset             = 0x0204,
>         .use_parent_regmap      = true,
>  };
>
> @@ -126,6 +174,38 @@ static const char *exynos_get_domain_name(struct device *dev,
>         return devm_kstrdup_const(dev, name, GFP_KERNEL);
>  }
>
> +static int exynos_pd_get_access_controller(struct exynos_pm_domain *pd)
> +{
> +       struct device_node *ac_np;
> +       struct resource ac_res;
> +       int ret;
> +
> +       ac_np = of_parse_phandle(pd->dev->of_node, "samsung,dtzpc", 0);
> +       if (!ac_np)
> +               return 0;
> +
> +       ret = of_address_to_resource(ac_np, 0, &ac_res);
> +       of_node_put(ac_np);
> +       if (ret)
> +               return dev_err_probe(pd->dev, ret,
> +                                    "failed to get access controller\n");
> +
> +       pd->ac_pa = ac_res.start;
> +
> +       /*
> +        * For some domains, TZ save/restore might not be implemented. If that
> +        * is the case, simply mark it as always on, as otherwise a power cycle
> +        * will lead to lost TZ configuration, making it impossible to access
> +        * registers from Linux afterwards.
> +        */
> +       if (exynos_pd_access_controller_power(pd, false) == -ENOENT) {
> +               pd->ac_pa = 0;
> +               pd->pd.flags |= GENPD_FLAG_ALWAYS_ON;
> +       }
> +
> +       return 0;
> +}
> +
>  static int exynos_pd_probe(struct platform_device *pdev)
>  {
>         const struct exynos_pm_domain_config *pm_domain_cfg;
> @@ -195,10 +275,14 @@ static int exynos_pd_probe(struct platform_device *pdev)
>
>         pd->pd.power_off = exynos_pd_power_off;
>         pd->pd.power_on = exynos_pd_power_on;
> -       pd->local_pwr_cfg = pm_domain_cfg->local_pwr_cfg;
> +       pd->cfg = pm_domain_cfg;
>         pd->configuration_reg += 0;
>         pd->status_reg += 4;
>
> +       ret = exynos_pd_get_access_controller(pd);
> +       if (ret)
> +               return ret;
> +
>         /*
>          * Some Samsung platforms with bootloaders turning on the splash-screen
>          * and handing it over to the kernel, requires the power-domains to be
> @@ -212,7 +296,7 @@ static int exynos_pd_probe(struct platform_device *pdev)
>         if (ret)
>                 return dev_err_probe(dev, ret, "failed to read status");
>
> -       on = val & pd->local_pwr_cfg;
> +       on = val & pd->cfg->local_pwr_cfg;
>
>         pm_genpd_init(&pd->pd, NULL, !on);
>         ret = of_genpd_add_provider_simple(np, &pd->pd);
>
> --
> 2.53.0.473.g4a7958ca14-goog
>