[PATCH v4 4/4] nvme-pci: Support shared tags across queues for Apple 2018 controllers

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

Another issue with the Apple T2 based 2018 controllers seem to be
that they blow up (and shut the machine down) if there's a tag
collision between the IO queue and the Admin queue.

My suspicion is that they use our tags for their internal tracking
and don't mix them with the queue id. They also seem to not like
when tags go beyond the IO queue depth, ie 128 tags.

This adds a quirk that marks tags 0..31 of the IO queue reserved

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Acked-by: Keith Busch <keith.busch@intel.com>
---
 drivers/nvme/host/nvme.h |  5 +++++
 drivers/nvme/host/pci.c  | 31 ++++++++++++++++++++++++++++++-
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 0925f7fc13ff..3e64f7187e70 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -102,6 +102,11 @@ enum nvme_quirks {
 	 * Use non-standard 128 bytes SQEs.
 	 */
 	NVME_QUIRK_128_BYTES_SQES		= (1 << 11),
+
+	/*
+	 * Prevent tag overlap between queues
+	 */
+	NVME_QUIRK_SHARED_TAGS                  = (1 << 12),
 };
 
 /*
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index c683263cdf60..de8c170d5abc 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2106,6 +2106,14 @@ static int nvme_setup_io_queues(struct nvme_dev *dev)
 	unsigned long size;
 
 	nr_io_queues = max_io_queues();
+
+	/*
+	 * If tags are shared with admin queue (Apple bug), then
+	 * make sure we only use one IO queue.
+	 */
+	if (dev->ctrl.quirks & NVME_QUIRK_SHARED_TAGS)
+		nr_io_queues = 1;
+
 	result = nvme_set_queue_count(&dev->ctrl, &nr_io_queues);
 	if (result < 0)
 		return result;
@@ -2276,6 +2284,14 @@ static int nvme_dev_add(struct nvme_dev *dev)
 		dev->tagset.flags = BLK_MQ_F_SHOULD_MERGE;
 		dev->tagset.driver_data = dev;
 
+		/*
+		 * Some Apple controllers requires tags to be unique
+		 * across admin and IO queue, so reserve the first 32
+		 * tags of the IO queue.
+		 */
+		if (dev->ctrl.quirks & NVME_QUIRK_SHARED_TAGS)
+			dev->tagset.reserved_tags = NVME_AQ_DEPTH;
+
 		ret = blk_mq_alloc_tag_set(&dev->tagset);
 		if (ret) {
 			dev_warn(dev->ctrl.device,
@@ -2356,6 +2372,18 @@ static int nvme_pci_enable(struct nvme_dev *dev)
                         "set queue depth=%u\n", dev->q_depth);
 	}
 
+	/*
+	 * Controllers with the shared tags quirk need the IO queue to be
+	 * big enough so that we get 32 tags for the admin queue
+	 */
+	if ((dev->ctrl.quirks & NVME_QUIRK_SHARED_TAGS) &&
+	    (dev->q_depth < (NVME_AQ_DEPTH + 2))) {
+		dev->q_depth = NVME_AQ_DEPTH + 2;
+		dev_warn(dev->ctrl.device, "IO queue depth clamped to %d\n",
+			 dev->q_depth);
+	}
+
+
 	nvme_map_cmb(dev);
 
 	pci_enable_pcie_error_reporting(pdev);
@@ -3057,7 +3085,8 @@ static const struct pci_device_id nvme_id_table[] = {
 	{ PCI_DEVICE(PCI_VENDOR_ID_APPLE, 0x2003) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_APPLE, 0x2005),
 		.driver_data = NVME_QUIRK_SINGLE_VECTOR |
-				NVME_QUIRK_128_BYTES_SQES },
+				NVME_QUIRK_128_BYTES_SQES |
+				NVME_QUIRK_SHARED_TAGS },
 	{ 0, }
 };
 MODULE_DEVICE_TABLE(pci, nvme_id_table);
-- 
2.17.1