[PATCH v5 6/6] firmware: qcom: scm: introduce keep_mdt_buf flag in PAS context

[Mukesh Ojha]

The PAS image initialization path always retains the metadata buffer
when a valid qcom_scm_pas_context is provided, even if the caller does
not require it. This implicit behavior leads to unclear buffer ownership
and forces new users of qcom_mdt_pas_load() to manually release
metadata, which is error‑ prone and incorrect.

Add a keep_mdt_buf flag to struct qcom_scm_pas_context to make metadata
retention explicit.  Metadata buffers are now freed by default and are
only preserved when this flag is set. qcom_q6v5_pas enables this during
probe for contexts that require retained metadata for subsequent PAS
operations, while existing callers continue to work unchanged.

Signed-off-by: Mukesh Ojha <mukesh.ojha@xxxxxxxxxxxxxxxx>
---
 drivers/firmware/qcom/qcom_scm.c       | 18 +++++++++++++++---
 drivers/remoteproc/qcom_q6v5_pas.c     |  3 +++
 include/linux/firmware/qcom/qcom_pas.h |  1 +
 3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/drivers/firmware/qcom/qcom_scm.c b/drivers/firmware/qcom/qcom_scm.c
index 16ae42e6c434..54ffec97cc26 100644
--- a/drivers/firmware/qcom/qcom_scm.c
+++ b/drivers/firmware/qcom/qcom_scm.c
@@ -625,7 +625,7 @@ static int qcom_scm_pas_prep_and_init_image(struct device *dev,
 	mdata_phys = qcom_tzmem_to_phys(mdata_buf);
 
 	ret = __qcom_scm_pas_init_image(dev, ctx->pas_id, mdata_phys, &res);
-	if (ret < 0)
+	if (ret < 0 || !ctx->keep_mdt_buf)
 		qcom_tzmem_free(mdata_buf);
 	else
 		ctx->ptr = mdata_buf;
@@ -664,9 +664,21 @@ static int qcom_scm_pas_init_image(struct device *dev, u32 pas_id,
 	memcpy(mdata_buf, metadata, size);
 
 	ret = __qcom_scm_pas_init_image(dev, pas_id, mdata_phys, &res);
-	if (ret < 0 || !ctx) {
+
+	/*
+	 * Some clients still pass the PAS context as NULL. Until all clients
+	 * switch to qcom_mdt_pas_load() and provide a valid PAS context, check
+	 * for NULL before dereferencing it.
+	 *
+	 * When a valid context is provided, keep_mdt_buf controls whether the
+	 * metadata buffer is retained after PAS_INIT. PAS remoteproc subsystems
+	 * set this flag so metadata persists until auth_and_reset() completes,
+	 * as TrustZone keeps the buffers locked until then. Other callers leave
+	 * it unset and metadata is freed immediately after the PAS_INIT call.
+	 */
+	if (ret < 0 || !ctx || !ctx->keep_mdt_buf) {
 		dma_free_coherent(dev, size, mdata_buf, mdata_phys);
-	} else if (ctx) {
+	} else {
 		ctx->ptr = mdata_buf;
 		ctx->phys = mdata_phys;
 		ctx->size = size;
diff --git a/drivers/remoteproc/qcom_q6v5_pas.c b/drivers/remoteproc/qcom_q6v5_pas.c
index 0391e30f42ba..38e6f6019825 100644
--- a/drivers/remoteproc/qcom_q6v5_pas.c
+++ b/drivers/remoteproc/qcom_q6v5_pas.c
@@ -722,6 +722,7 @@ static int qcom_pas_alloc_memory_region(struct qcom_pas *pas)
 	if (IS_ERR(pas->pas_ctx))
 		return PTR_ERR(pas->pas_ctx);
 
+	pas->pas_ctx->keep_mdt_buf = true;
 	if (!pas->dtb_pas_id)
 		return 0;
 
@@ -740,6 +741,8 @@ static int qcom_pas_alloc_memory_region(struct qcom_pas *pas)
 	if (IS_ERR(pas->dtb_pas_ctx))
 		return PTR_ERR(pas->dtb_pas_ctx);
 
+	pas->dtb_pas_ctx->keep_mdt_buf = true;
+
 	return 0;
 }
 
diff --git a/include/linux/firmware/qcom/qcom_pas.h b/include/linux/firmware/qcom/qcom_pas.h
index fb2ec3be6a16..1d132e89536e 100644
--- a/include/linux/firmware/qcom/qcom_pas.h
+++ b/include/linux/firmware/qcom/qcom_pas.h
@@ -22,6 +22,7 @@ struct qcom_pas_context {
 	dma_addr_t phys;
 	ssize_t size;
 	bool use_tzmem;
+	bool keep_mdt_buf;
 };
 
 static inline void __iomem *qcom_pas_ctx_map(struct qcom_pas_context *ctx)
-- 
2.53.0