fix(ufs): fix cache maintenance issues
Fix software cache maintenance issues that can happen when
cpu prefetches data before DMA operations are complete.
This change fixes two cases one for ufs_read_blocks and
other for ufs_check_resp, in both cases invalidation of
buffer was done before the DMA operation completed.
This caused cpu prefetcher to bring data into cache
before DMA completed and caused UFS read failures.
The changes also removes unwanted cache operations to
local variable utrd which is not consumed by UFS host
controller and zeroing out buffer in ufs_read_capacity.
Change-Id: I9a288eb19d6705f6fa8bdb0b817a6411235fd8b6
Signed-off-by: Channagoud kadabi <kadabi@google.com>
diff --git a/drivers/ufs/ufs.c b/drivers/ufs/ufs.c
index 3d6d99f..be6bc4a 100644
--- a/drivers/ufs/ufs.c
+++ b/drivers/ufs/ufs.c
@@ -356,7 +356,6 @@
hd->prdto = (utrd->size_upiu + utrd->size_resp_upiu) >> 2;
}
- flush_dcache_range((uintptr_t)utrd, sizeof(utp_utrd_t));
flush_dcache_range((uintptr_t)utrd->header, UFS_DESC_SIZE);
return 0;
}
@@ -415,7 +414,6 @@
assert(0);
break;
}
- flush_dcache_range((uintptr_t)utrd, sizeof(utp_utrd_t));
flush_dcache_range((uintptr_t)utrd->header, UFS_DESC_SIZE);
return 0;
}
@@ -439,7 +437,6 @@
nop_out->trans_type = 0;
nop_out->task_tag = utrd->task_tag;
- flush_dcache_range((uintptr_t)utrd, sizeof(utp_utrd_t));
flush_dcache_range((uintptr_t)utrd->header, UFS_DESC_SIZE);
}
@@ -473,7 +470,6 @@
hd = (utrd_header_t *)utrd->header;
resp = (resp_upiu_t *)utrd->resp_upiu;
- inv_dcache_range((uintptr_t)hd, UFS_DESC_SIZE);
do {
data = mmio_read_32(ufs_params.reg_base + IS);
if ((data & ~(UFS_INT_UCCS | UFS_INT_UTRCS)) != 0)
@@ -483,6 +479,12 @@
data = mmio_read_32(ufs_params.reg_base + UTRLDBR);
assert((data & (1 << slot)) == 0);
+ /*
+ * Invalidate the header after DMA read operation has
+ * completed to avoid cpu referring to the prefetched
+ * data brought in before DMA completion.
+ */
+ inv_dcache_range((uintptr_t)hd, UFS_DESC_SIZE);
assert(hd->ocs == OCS_SUCCESS);
assert((resp->trans_type & TRANS_TYPE_CODE_MASK) == trans_type);
(void)resp;
@@ -660,8 +662,6 @@
buf = (uintptr_t)data;
buf = (buf + CACHE_WRITEBACK_GRANULE - 1) &
~(CACHE_WRITEBACK_GRANULE - 1);
- memset((void *)buf, 0, CACHE_WRITEBACK_GRANULE);
- flush_dcache_range(buf, CACHE_WRITEBACK_GRANULE);
do {
get_utrd(&utrd);
ufs_prepare_cmd(&utrd, CDBCMD_READ_CAPACITY_10, lun, 0,
@@ -710,6 +710,11 @@
#ifdef UFS_RESP_DEBUG
dump_upiu(&utrd);
#endif
+ /*
+ * Invalidate prefetched cache contents before cpu
+ * accesses the buf.
+ */
+ inv_dcache_range(buf, size);
resp = (resp_upiu_t *)utrd.resp_upiu;
(void)result;
return size - resp->res_trans_cnt;