Re: [PATCH v5 3/3] nvmem: stm32: detect bsec pta presence for STM32MP15x

[Etienne Carriere]

On Fri, 6 Jan 2023 at 18:04, Patrick Delaunay
<patrick.delaunay@xxxxxxxxxxx> wrote:
>
> On STM32MP15x SoC, the SMC backend is optional when OP-TEE is used;
> the PTA BSEC should be used as it is done on STM32MP13x platform,
> but the BSEC SMC can be also used: it is a legacy mode in OP-TEE,
> not recommended but used in previous OP-TEE firmware.
>
> The presence of OP-TEE is dynamically detected in STM32MP15x device tree
> and the supported NVMEM backend is dynamically detected:
> - PTA with stm32_bsec_pta_find
> - SMC with stm32_bsec_check
>
> With OP-TEE but without PTA and SMC detection, the probe is deferred for
> STM32MP15x devices.
>
> On STM32MP13x platform, only the PTA is supported with cfg->ta = true
> and this detection is skipped.
>
> Signed-off-by: Patrick Delaunay <patrick.delaunay@xxxxxxxxxxx>
> ---
>
> Changes in v5:
> - update the BSEC SMC detection logic in stm32_romem_probe()
>   after Etienne Carierre review to support NVMEM probe after OP-TEE probe
>
> Changes in v3:
> - use of_find_compatible_node in optee_presence_check function
>   instead of of_find_node_by_path("/firmware/optee")
>
> Changes in v2:
> - Added patch in the serie for BSEC PTA support on STM32MP15x
>   with dynamic detection of OP-TEE presence and SMC support (legacy mode)
>
>  drivers/nvmem/stm32-romem.c | 38 +++++++++++++++++++++++++++++++++----
>  1 file changed, 34 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/nvmem/stm32-romem.c b/drivers/nvmem/stm32-romem.c
> index 978a63edf297..e0babc2cebd7 100644
> --- a/drivers/nvmem/stm32-romem.c
> +++ b/drivers/nvmem/stm32-romem.c
> @@ -159,6 +159,31 @@ static int stm32_bsec_pta_write(void *context, unsigned int offset, void *buf,
>         return stm32_bsec_optee_ta_write(priv->ctx, priv->lower, offset, buf, bytes);
>  }
>
> +static bool stm32_bsec_smc_check(void)
> +{
> +       u32 val;
> +       int ret;
> +
> +       /* check that the OP-TEE support the BSEC SMC (legacy mode) */
> +       ret = stm32_bsec_smc(STM32_SMC_READ_SHADOW, 0, 0, &val);
> +
> +       return !ret;
> +}
> +
> +static bool optee_presence_check(void)
> +{
> +       struct device_node *np;
> +       bool tee_detected = false;
> +
> +       /* check that the OP-TEE node is present and available. */
> +       np = of_find_compatible_node(NULL, NULL, "linaro,optee-tz");
> +       if (np && of_device_is_available(np))
> +               tee_detected = true;
> +       of_node_put(np);
> +
> +       return tee_detected;
> +}
> +
>  static int stm32_romem_probe(struct platform_device *pdev)
>  {
>         const struct stm32_romem_cfg *cfg;
> @@ -195,11 +220,16 @@ static int stm32_romem_probe(struct platform_device *pdev)
>         } else {
>                 priv->cfg.size = cfg->size;
>                 priv->lower = cfg->lower;
> -               if (cfg->ta) {
> +               if (cfg->ta || optee_presence_check()) {
>                         rc = stm32_bsec_optee_ta_open(&priv->ctx);
> -                       /* wait for OP-TEE client driver to be up and ready */
> -                       if (rc)
> -                               return rc;
> +                       if (rc) {
> +                               /* wait for OP-TEE client driver to be up and ready */
> +                               if (rc == -EPROBE_DEFER)
> +                                       return -EPROBE_DEFER;
> +                               /* BSEC PTA is required or SMC not ready */

Nitpicking: I would replace "SMC not ready" with "SMC not supported".
Aside that, Reviewed-by: Etienne Carriere <etienne.carriere@xxxxxxxxxx>


> +                               if (cfg->ta || !stm32_bsec_smc_check())
> +                                       return rc;
> +                       }
>                 }
>                 if (priv->ctx) {
>                         rc = devm_add_action_or_reset(dev, stm32_bsec_optee_ta_close, priv->ctx);
> --
> 2.25.1
>