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Subject[PATCH v3 3/3] nvmem: stm32: detect bsec pta presence for STM32MP15x
Date
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@foss.st.com>
---

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 | 33 +++++++++++++++++++++++++++++++--
1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/drivers/nvmem/stm32-romem.c b/drivers/nvmem/stm32-romem.c
index e2fb3eb747dd..f8b8de54b033 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;
@@ -195,10 +220,14 @@ 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)
+ if (rc == -EPROBE_DEFER) {
+ /* BSEC PTA is required or SMC not ready */
+ if (cfg->ta || !stm32_bsec_smc_check())
+ return -EPROBE_DEFER;
+ } else if (rc)
return rc;
rc = devm_add_action_or_reset(dev, stm32_bsec_optee_ta_close, priv->ctx);
if (rc) {
--
2.25.1
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