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[v3] scsi: ufs: mcq: Limit the amount of inflight requests

Message ID 20230420101116.173-1-avri.altman@wdc.com
State New
Headers show
Series [v3] scsi: ufs: mcq: Limit the amount of inflight requests | expand

Commit Message

Avri Altman April 20, 2023, 10:11 a.m. UTC 
in UFS, each request is designated via the triplet <iid, lun, task tag>.

In UFS4.0 the Initiator ID field is 8 bits wide, comprised of the
EXT_IID and IID fields. Together with the task tag (single byte), they
limit the driver's hw queues capacity.

The purpose of this patch is to document the ufs spec restrictions.
practically, it impose no functional change because a) the current hw
supports much less (merely 64 requests), and b) since shost->host_tagset
is set - then the number of inflight IOs is limited by just the HW queue
depth.

---
v2 -> v3:
fix smatch warnings (Dan Carpenter)
elaborate commit log (John Garry)

v1 -> v2:
Attend Johannes's and Bart's comments

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Avri Altman <avri.altman@wdc.com>
---
 drivers/ufs/core/ufshcd.c | 6 ++++++
 1 file changed, 6 insertions(+)
diff mbox series

Patch

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 03c47f9a2750..9cebec6be35c 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -8468,6 +8468,12 @@  static int ufshcd_alloc_mcq(struct ufs_hba *hba)
 	if (ret)
 		goto err;
 
+	if (hba->nutrs * hba->nr_hw_queues > SZ_64K - 1) {
+		dev_info(hba->dev, "there can be at most 64K inflight requests\n");
+		ret = -EINVAL;
+		goto err;
+	}
+
 	/*
 	 * Previously allocated memory for nutrs may not be enough in MCQ mode.
 	 * Number of supported tags in MCQ mode may be larger than SDB mode.