[PATCH 1/2] nvme-apple: Only limit admin queue tag space when with Linear SQ is present

[Nick Chan]

Apple NVMe controllers require tags of pending commands to not be shared
across admin and IO queues. However, on Apple A11 without linear SQ, it is
not possible for either queue to skip over some tags and must go from 0 to
the configured maximum before wrapping around.

As a result, in order to prevent tag collision, dynamic tag reservation
while a command is in-flight becomes necessary. In this context, there is
no reason to limit the admin queue's tag space, as it is not helpful in
preventing tag collision.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 04d8ecf37b5e ("nvme: apple: Add Apple A11 support")
Signed-off-by: Nick Chan <towinchenmi@xxxxxxxxx>
---
 drivers/nvme/host/apple.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/apple.c b/drivers/nvme/host/apple.c
index c692fc73babf..c1115e27a0d6 100644
--- a/drivers/nvme/host/apple.c
+++ b/drivers/nvme/host/apple.c
@@ -1303,7 +1303,10 @@ static int apple_nvme_alloc_tagsets(struct apple_nvme *anv)
 
 	anv->admin_tagset.ops = &apple_nvme_mq_admin_ops;
 	anv->admin_tagset.nr_hw_queues = 1;
-	anv->admin_tagset.queue_depth = APPLE_NVME_AQ_MQ_TAG_DEPTH;
+	if (anv->hw->has_lsq_nvmmu)
+		anv->admin_tagset.queue_depth = APPLE_NVME_AQ_MQ_TAG_DEPTH;
+	else
+		anv->admin_tagset.queue_depth = anv->hw->max_queue_depth - 1;
 	anv->admin_tagset.timeout = NVME_ADMIN_TIMEOUT;
 	anv->admin_tagset.numa_node = NUMA_NO_NODE;
 	anv->admin_tagset.cmd_size = sizeof(struct apple_nvme_iod);

-- 
2.54.0