[PATCH] misc: fastrpc: Don't fail probe when the SDSP memory assign fails

[David Heidelberg via B4 Relay]

From: David Heidelberg <david@xxxxxxx>

A failed qcom_scm_assign_mem() aborts fastrpc_rpmsg_probe(). On SDM845 this
turns every SLPI subsystem restart into an endless probe failure loop:

 remoteproc3: crash detected in slpi: type fatal error
 remoteproc3: remote processor slpi is now up
 qcom_scm firmware:scm: Assign memory protection call failed -22
 qcom,fastrpc 5c00000.remoteproc:glink-edge.fastrpcglink-apps-dsp.-1.-1: probe with driver qcom,fastrpc failed with error -22
 qcom,fastrpc 5c00000.remoteproc:glink-edge.fastrpcglink-apps-dsp.-1.-1: rpmsg_dev_probe: failed: -22

The first assign succeeds and hands the reserved region to the VMIDs
described in qcom,vmids. qcom_scm_assign_mem() reports the resulting
owner set back through @srcvm, but the driver discards it, and nothing
reverses the assignment in fastrpc_rpmsg_remove(). When the glink
channel is re-announced after a subsystem restart, probe passes
src_perms = BIT(QCOM_SCM_VMID_HLOS) again, which no longer describes the
region, and the firmware rejects the call with -EINVAL.

At that point the region is already assigned, and HLOS is part of the
destination VMID list, so both the host and the DSP keep access. Failing
the probe only removes /dev/fastrpc-sdsp and makes the remote reopen the
channel, repeating the cycle indefinitely. Warn and continue instead

Assisted-by: LLM
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 6a502776f4a4 ("misc: fastrpc: check qcom_scm_assign_mem() return in rpmsg_probe")
Signed-off-by: David Heidelberg <david@xxxxxxx>
---
Tracking the current owner set so the re-assign is issued with the
correct source VMIDs is a separate fix, but I assume it would make sense
to keep that to someone with more knowledge of fastrpc.

I aim here to reverting into usable state again which can be also
backported.

Tested on Pixel 3 and 3 XL.
---
 drivers/misc/fastrpc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index 90fd669636ec1..41943a3d496af 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -2590,17 +2590,19 @@ static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
 
 		err = of_reserved_mem_region_to_resource(rdev->of_node, 0, &res);
 		if (!err) {
 			src_perms = BIT(QCOM_SCM_VMID_HLOS);
 
 			err = qcom_scm_assign_mem(res.start, resource_size(&res), &src_perms,
 				    data->vmperms, data->vmcount);
 			if (err)
-				goto err_free_data;
+				dev_warn(rdev,
+					 "assign memory to SDSP failed: %d\n",
+					 err);
 		}
 
 	}
 
 	secure_dsp = !(of_property_read_bool(rdev->of_node, "qcom,non-secure-domain"));
 	data->secure = secure_dsp;
 	data->soc_data = soc_data;
 	data->poll_mode_supported = soc_data->poll_mode_supported ||

---
base-commit: 7079a12d7506b07fb53b54a664bfad5fa9b16d70
change-id: 20260923-fastrpc-fail-slow-4dc839c1685c

Best regards,
--  
David Heidelberg <david@xxxxxxx>