drm/amdgpu/vcn: Document IRQ per-instance irq behavior for VCN 4.0.3

When examining the VCN function init, it is common to find a loop that
initializes VCN rings, which uses one IRQ per instance. However, VCN
4.0.3 deviates from this pattern, as it includes a distinct field to
differentiate instances, which results in a slightly different ring
init. This commit makes this difference explicit by using a fixed index
when initializing the ring buffer and also adds a comment.

Signed-off-by: Rodrigo Siqueira <siqueira@igalia.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v4_0_3.c b/drivers/gpu/drm/amd/amdgpu/vcn_v4_0_3.c
index 7b93a275ec4f9e89c00d0b33a9889e1af83724f9..bae1ad4484edea6c087ae170ba15a707d3767fba 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/vcn_v4_0_3.c
+++ b/drivers/gpu/drm/amd/amdgpu/vcn_v4_0_3.c
@@ -212,7 +212,11 @@ static int vcn_v4_0_3_sw_init(struct amdgpu_ip_block *ip_block)
 
                ring->vm_hub = AMDGPU_MMHUB0(adev->vcn.inst[i].aid_id);
                sprintf(ring->name, "vcn_unified_%d", adev->vcn.inst[i].aid_id);
-               r = amdgpu_ring_init(adev, ring, 512, &adev->vcn.inst->irq, 0,
+
+               /* There are no per-instance irq source IDs on 4.0.3, the IH
+                * packets use a separate field to differentiate instances.
+                */
+               r = amdgpu_ring_init(adev, ring, 512, &adev->vcn.inst[0].irq, 0,
                                     AMDGPU_RING_PRIO_DEFAULT,
                                     &adev->vcn.inst[i].sched_score);
                if (r)