2023-06-01 11:41:08

by Bao D. Nguyen

Subject: [PATCH v1 1/1] ufs: mcq: Fix the variable wraparound logic

If the hwq's queue depth is not a multiple of 4s, the
logic used for wrapping around the increase-by-1 sq_head_slot
variable in ufshcd_mcq_sqe_search() will give an incorrect
result because the binary expression of the mask is not
a uniform of all 1s.

Signed-off-by: Bao D. Nguyen <[email protected]>
---
drivers/ufs/core/ufs-mcq.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/ufs/core/ufs-mcq.c b/drivers/ufs/core/ufs-mcq.c
index 66ac02e..8e5bc88 100644
--- a/drivers/ufs/core/ufs-mcq.c
+++ b/drivers/ufs/core/ufs-mcq.c
@@ -585,7 +585,6 @@ static bool ufshcd_mcq_sqe_search(struct ufs_hba *hba,
{
struct ufshcd_lrb *lrbp = &hba->lrb[task_tag];
struct utp_transfer_req_desc *utrd;
- u32 mask = hwq->max_entries - 1;
__le64 cmd_desc_base_addr;
bool ret = false;
u64 addr, match;
@@ -610,7 +609,10 @@ static bool ufshcd_mcq_sqe_search(struct ufs_hba *hba,
ret = true;
goto out;
}
- sq_head_slot = (sq_head_slot + 1) & mask;
+
+ sq_head_slot++;
+ if (sq_head_slot == hwq->max_entries)
+ sq_head_slot = 0;
}

out:
--
2.7.4

2023-06-01 12:12:09

by Bao D. Nguyen

Subject: Re: [PATCH v1 1/1] ufs: mcq: Fix the variable wraparound logic

Please ignore this duplicate patch. My apologies.

Thanks,
Bao

On 6/1/2023 4:27 AM, Bao D. Nguyen wrote:
> If the hwq's queue depth is not a multiple of 4s, the
> logic used for wrapping around the increase-by-1 sq_head_slot
> variable in ufshcd_mcq_sqe_search() will give an incorrect
> result because the binary expression of the mask is not
> a uniform of all 1s.
>
> Signed-off-by: Bao D. Nguyen <[email protected]>
> ---
> drivers/ufs/core/ufs-mcq.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/ufs/core/ufs-mcq.c b/drivers/ufs/core/ufs-mcq.c
> index 66ac02e..8e5bc88 100644
> --- a/drivers/ufs/core/ufs-mcq.c
> +++ b/drivers/ufs/core/ufs-mcq.c
> @@ -585,7 +585,6 @@ static bool ufshcd_mcq_sqe_search(struct ufs_hba *hba,
> {
> struct ufshcd_lrb *lrbp = &hba->lrb[task_tag];
> struct utp_transfer_req_desc *utrd;
> - u32 mask = hwq->max_entries - 1;
> __le64 cmd_desc_base_addr;
> bool ret = false;
> u64 addr, match;
> @@ -610,7 +609,10 @@ static bool ufshcd_mcq_sqe_search(struct ufs_hba *hba,
> ret = true;
> goto out;
> }
> - sq_head_slot = (sq_head_slot + 1) & mask;
> +
> + sq_head_slot++;
> + if (sq_head_slot == hwq->max_entries)
> + sq_head_slot = 0;
> }
>
> out: