linux-kernel - [PATCH 5.10 141/299] drm/amdgpu: mask the xgmi number of hops reported from psp to kfd

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Date:   Mon, 10 May 2021 12:18:58 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jonathan Kim <jonathan.kim@....com>,
        Amber Lin <amber.lin@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 141/299] drm/amdgpu: mask the xgmi number of hops reported from psp to kfd

From: Jonathan Kim <jonathan.kim@....com>

[ Upstream commit 4ac5617c4b7d0f0a8f879997f8ceaa14636d7554 ]

The psp supplies the link type in the upper 2 bits of the psp xgmi node
information num_hops field.  With a new link type, Aldebaran has these
bits set to a non-zero value (1 = xGMI3) so the KFD topology will report
the incorrect IO link weights without proper masking.
The actual number of hops is located in the 3 least significant bits of
this field so mask if off accordingly before passing it to the KFD.

Signed-off-by: Jonathan Kim <jonathan.kim@....com>
Reviewed-by: Amber Lin <amber.lin@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c
index 1162913c8bf4..0526dec1d736 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c
@@ -465,15 +465,22 @@ int amdgpu_xgmi_update_topology(struct amdgpu_hive_info *hive, struct amdgpu_dev
 }
 
 
+/*
+ * NOTE psp_xgmi_node_info.num_hops layout is as follows:
+ * num_hops[7:6] = link type (0 = xGMI2, 1 = xGMI3, 2/3 = reserved)
+ * num_hops[5:3] = reserved
+ * num_hops[2:0] = number of hops
+ */
 int amdgpu_xgmi_get_hops_count(struct amdgpu_device *adev,
 		struct amdgpu_device *peer_adev)
 {
 	struct psp_xgmi_topology_info *top = &adev->psp.xgmi_context.top_info;
+	uint8_t num_hops_mask = 0x7;
 	int i;
 
 	for (i = 0 ; i < top->num_nodes; ++i)
 		if (top->nodes[i].node_id == peer_adev->gmc.xgmi.node_id)
-			return top->nodes[i].num_hops;
+			return top->nodes[i].num_hops & num_hops_mask;
 	return	-EINVAL;
 }
 
-- 
2.30.2