Messages in this thread | | | Date | Mon, 3 Apr 2023 09:52:33 +0100 | Subject | Re: [PATCH v2] scsi: ufs: mcq: Limit the amount of inflight requests | From | John Garry <> |
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On 31/03/2023 08:46, Avri Altman wrote: > 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. > > --- > v1 -> v2: > Attend Johannes's and Bart's comments > > Signed-off-by: Avri Altman <avri.altman@wdc.com> > --- > drivers/ufs/core/ufshcd.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c > index 35a3bd95c5e4..cac7c9918c5b 100644 > --- a/drivers/ufs/core/ufshcd.c > +++ b/drivers/ufs/core/ufshcd.c > @@ -8468,6 +8468,11 @@ static int ufshcd_alloc_mcq(struct ufs_hba *hba) > if (ret) > goto err; > > + if (hba->nutrs * hba->nr_hw_queues > SZ_64K - 1) {
If shost->host_tagset is set - which it seems to be for this driver - then the number of HW queues would not influence how many IOs the host may be sent. Rather this is just limited by just the HW queue depth.
Thanks, John
> + dev_info(hba->dev, "there can be at most 64K inflight requests\n"); > + 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.
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