On 23.09.26 00:38, David Heidelberg via B4 Relay wrote:
From: David Heidelberg <[email protected]>

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: [email protected]
Fixes: 6a502776f4a4 ("misc: fastrpc: check qcom_scm_assign_mem() return in 
rpmsg_probe")
Signed-off-by: David Heidelberg <[email protected]>
---
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 <[email protected]>

I've had a similar issue on sm8250. There the downstream devicetree mapped fastrpc-mem over the whole memory but only used a small part of it as defined in qcom,iommu-dma-addr-pool. Redefining fastrpc_mem to only use that range fixed the problem.

commit 946f65f7f3300741a2c0b6eb0248ccd19eca1925
Author: Frieder Hannenheim <[email protected]>
Date:   Thu Aug 6 20:04:08 2026 +0200

    sm8250.dtsi: correct fastrpc_mem

    - fixes spli bringup

diff --git a/arch/arm64/boot/dts/qcom/sm8250.dtsi b/arch/arm64/boot/dts/qcom/sm8250.dtsi
index c490815ee3a2..f3ac307ed1db 100644
--- a/arch/arm64/boot/dts/qcom/sm8250.dtsi
+++ b/arch/arm64/boot/dts/qcom/sm8250.dtsi
@@ -866,9 +866,8 @@ cdsp_secure_heap: memory@8bf00000 {

                fastrpc_mem: fastrpc {
                        compatible = "shared-dma-pool";
-                       alloc-ranges = <0x0 0x00000000 0x0 0xffffffff>;
-                       alignment = <0x0 0x400000>;
-                       size = <0x0 0x2000000>;
+                       alloc-ranges = <0x80000000 0x78000000>;
+                       alignment = <0x400000>;
                        reusable;
                };
        };

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