misc: fastrpc: support complete DMA pool access to the DSP

To support FastRPC Context Banks which aren't mapped via the SMMU,
make the whole reserved memory region available to the DSP to allow
access to coherent buffers.

This is performed by assigning the memory to the DSP via a hypervisor
call to set the correct permissions for the Virtual Machines on the DSP.
This is only necessary when a memory region is provided for SLPI DSPs
so guard this with a domain ID check.

Signed-off-by: Dylan Van Assche <me@dylanvanassche.be>
Reviewed-by: Caleb Connolly <caleb.connolly@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Ekansh Gupta <quic_ekangupt@quicinc.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20240705075900.424100-5-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: DylanVanAssche

drivers/misc/fastrpc.c

@@ -2250,6 +2250,8 @@ static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
 	int i, err, domain_id = -1, vmcount;
 	const char *domain;
 	bool secure_dsp;
+	struct device_node *rmem_node;
+	struct reserved_mem *rmem;
 	unsigned int vmids[FASTRPC_MAX_VMIDS];
 
 	err = of_property_read_string(rdev->of_node, "label", &domain);
@@ -2292,6 +2294,23 @@ static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
 		}
 	}
 
+	rmem_node = of_parse_phandle(rdev->of_node, "memory-region", 0);
+	if (domain_id == SDSP_DOMAIN_ID && rmem_node) {
+		u64 src_perms;
+
+		rmem = of_reserved_mem_lookup(rmem_node);
+		if (!rmem) {
+			err = -EINVAL;
+			goto fdev_error;
+		}
+
+		src_perms = BIT(QCOM_SCM_VMID_HLOS);
+
+		qcom_scm_assign_mem(rmem->base, rmem->size, &src_perms,
+				    data->vmperms, data->vmcount);
+
+	}
+
 	secure_dsp = !(of_property_read_bool(rdev->of_node, "qcom,non-secure-domain"));
 	data->secure = secure_dsp;