Some SoCs could require one scatterlist entry for smaller than
page size, i.e. 4KB. For the cases of dispatching commands
with more than one scatterlist entry and under 4KB size,
They could behave as follows:
Given that a command to read something
from device is dispatched with two scatterlist entries that
are named AAA and BBB. After dispatching, host builds two PRDT
entries and during transmission, device sends just one DATA IN
because device doesn't care on host dma. The host then tranfers
the whole data from start address of the area named AAA.
In consequence, the area that follows AAA would be corrupted.
|<------------->|
+-------+------------ +-------+
+ AAA + (corrupted) ... + BBB +
+-------+------------ +-------+
In this case, you need to force an aligment with page size for
sg entries.
Signed-off-by: Kiwoong Kim <kwmad.kim@xxxxxxxxxxx>
---
drivers/scsi/ufs/ufshcd.c | 2 ++
drivers/scsi/ufs/ufshcd.h | 4 ++++
2 files changed, 6 insertions(+)
diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index e221add..847eb02 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -4792,6 +4792,8 @@ static int ufshcd_slave_configure(struct scsi_device *sdev)
struct request_queue *q = sdev->request_queue;
blk_queue_update_dma_pad(q, PRDT_DATA_BYTE_COUNT_PAD - 1);
+ if (hba->quirks & UFSHCD_QUIRK_ALIGN_SG_WITH_PAGE_SIZE)
+ blk_queue_update_dma_alignment(q, PAGE_SIZE - 1);
if (ufshcd_is_rpm_autosuspend_allowed(hba))
sdev->rpm_autosuspend = 1;
diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
index 9bb5f0e..9e7223f 100644
--- a/drivers/scsi/ufs/ufshcd.h
+++ b/drivers/scsi/ufs/ufshcd.h
@@ -549,6 +549,10 @@ enum ufshcd_quirks {
*/
UFSHCI_QUIRK_SKIP_MANUAL_WB_FLUSH_CTRL = 1 << 12,
+ /*
+ * This quirk allows only sg entries aligned with page size.
+ */
+ UFSHCD_QUIRK_ALIGN_SG_WITH_PAGE_SIZE = 1 << 13,
};
enum ufshcd_caps {
--
2.7.4
