soc: qcom: rmtfs-mem: Add support for assigning memory to remote

On some platform the remote processor's memory map is not statically
configured in TrustZone, so each memory region that is to be accessed by
the remote needs a call into TrustZone to set up the remote's
permissions.

Implement this for the rmtfs memory driver, to give the modem on 8996
access to the shared file system buffers.
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>

drivers/soc/qcom/Kconfig

@@ -47,6 +47,7 @@ config QCOM_QMI_HELPERS
 config QCOM_RMTFS_MEM
 	tristate "Qualcomm Remote Filesystem memory driver"
 	depends on ARCH_QCOM
+	select QCOM_SCM
 	help
 	  The Qualcomm remote filesystem memory driver is used for allocating
 	  and exposing regions of shared memory with remote processors for the

drivers/soc/qcom/rmtfs_mem.c

@@ -37,6 +37,8 @@ struct qcom_rmtfs_mem {
 	phys_addr_t size;
 
 	unsigned int client_id;
+
+	unsigned int perms;
 };
 
 static ssize_t qcom_rmtfs_mem_show(struct device *dev,
@@ -151,9 +153,11 @@ static void qcom_rmtfs_mem_release_device(struct device *dev)
 static int qcom_rmtfs_mem_probe(struct platform_device *pdev)
 {
 	struct device_node *node = pdev->dev.of_node;
+	struct qcom_scm_vmperm perms[2];
 	struct reserved_mem *rmem;
 	struct qcom_rmtfs_mem *rmtfs_mem;
 	u32 client_id;
+	u32 vmid;
 	int ret;
 
 	rmem = of_reserved_mem_lookup(node);
@@ -204,10 +208,31 @@ static int qcom_rmtfs_mem_probe(struct platform_device *pdev)
 
 	rmtfs_mem->dev.release = qcom_rmtfs_mem_release_device;
 
+	ret = of_property_read_u32(node, "qcom,vmid", &vmid);
+	if (ret < 0 && ret != -EINVAL) {
+		dev_err(&pdev->dev, "failed to parse qcom,vmid\n");
+		goto remove_cdev;
+	} else if (!ret) {
+		perms[0].vmid = QCOM_SCM_VMID_HLOS;
+		perms[0].perm = QCOM_SCM_PERM_RW;
+		perms[1].vmid = vmid;
+		perms[1].perm = QCOM_SCM_PERM_RW;
+
+		rmtfs_mem->perms = BIT(QCOM_SCM_VMID_HLOS);
+		ret = qcom_scm_assign_mem(rmtfs_mem->addr, rmtfs_mem->size,
+					  &rmtfs_mem->perms, perms, 2);
+		if (ret < 0) {
+			dev_err(&pdev->dev, "assign memory failed\n");
+			goto remove_cdev;
+		}
+	}
+
 	dev_set_drvdata(&pdev->dev, rmtfs_mem);
 
 	return 0;
 
+remove_cdev:
+	cdev_device_del(&rmtfs_mem->cdev, &rmtfs_mem->dev);
 put_device:
 	put_device(&rmtfs_mem->dev);
 
@@ -217,6 +242,15 @@ static int qcom_rmtfs_mem_probe(struct platform_device *pdev)
 static int qcom_rmtfs_mem_remove(struct platform_device *pdev)
 {
 	struct qcom_rmtfs_mem *rmtfs_mem = dev_get_drvdata(&pdev->dev);
+	struct qcom_scm_vmperm perm;
+
+	if (rmtfs_mem->perms) {
+		perm.vmid = QCOM_SCM_VMID_HLOS;
+		perm.perm = QCOM_SCM_PERM_RW;
+
+		qcom_scm_assign_mem(rmtfs_mem->addr, rmtfs_mem->size,
+				    &rmtfs_mem->perms, &perm, 1);
+	}
 
 	cdev_device_del(&rmtfs_mem->cdev, &rmtfs_mem->dev);
 	put_device(&rmtfs_mem->dev);