Re: [PATCH v6 04/10] scsi: ufs: introduce UFSHCD_QUIRK_PRDT_BYTE_GRAN quirk

Christoph Hellwig
2020-04-22T06:54:16Z

On Fri, Apr 17, 2020 at 11:29:38PM +0530, Alim Akhtar wrote:
> Some UFS host controllers may think granularities of PRDT length and
> offset as bytes, not double words.
>
> Signed-off-by: Kiwoong Kim <kwmad.kim@samsung.com>
> Signed-off-by: Alim Akhtar <alim.akhtar@samsung.com>
> ---
> drivers/scsi/ufs/ufshcd.c | 30 +++++++++++++++++++++++-------
> drivers/scsi/ufs/ufshcd.h | 6 ++++++
> 2 files changed, 29 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index ee30ed6cc805..b32fcedcdcb9 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -2151,8 +2151,14 @@ static int ufshcd_map_sg(struct ufs_hba *hba, struct ufshcd_lrb *lrbp)
> return sg_segments;
>
> if (sg_segments) {
> - lrbp->utr_descriptor_ptr->prd_table_length =
> - cpu_to_le16((u16)sg_segments);
> +
> + if (hba->quirks & UFSHCD_QUIRK_PRDT_BYTE_GRAN)
> + lrbp->utr_descriptor_ptr->prd_table_length =
> + cpu_to_le16((u16)(sg_segments *
> + sizeof(struct ufshcd_sg_entry)));
> + else
> + lrbp->utr_descriptor_ptr->prd_table_length =
> + cpu_to_le16((u16) (sg_segments));

No double words here. "Normal" UFS uses the actual segment count,
while Samsumg uses bytes. Also no need fo the u16 count in
either the old or new version.