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authorVasanthy Kolluri <vkolluri@cisco.com>2010-03-18 16:19:44 +0000
committerDavid S. Miller <davem@davemloft.net>2010-03-18 21:22:47 -0700
commita55a603dae47a1ea4fbfad3a3a428ea7a0900ab6 (patch)
treee5a0526197efe4afb24443a2b918a8908ce11a43 /drivers/net/enic/cq_enet_desc.h
parentba7e94a44afbbf4c494e00b844f7bbfb144e7f6d (diff)
enic: Bug Fix: Fix hardware descriptor reads
The last bit written to a completion descriptor by hardware is the color bit. Driver must read all other descriptor fields only after reading the color bit to avoid reading stale descriptor fields. There is a rmb() after reading the color bit to avoid any compiler/cpu reordering of the reads. The color bit is the generation bit that toggles each pass through the completion descriptor ring. Signed-off-by: Scott Feldman <scofeldm@cisco.com> Signed-off-by: Vasanthy Kolluri <vkolluri@cisco.com> Signed-off-by: Roopa Prabhu <roprabhu@cisco.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/enic/cq_enet_desc.h')
-rw-r--r--drivers/net/enic/cq_enet_desc.h12
1 files changed, 8 insertions, 4 deletions
diff --git a/drivers/net/enic/cq_enet_desc.h b/drivers/net/enic/cq_enet_desc.h
index 03dce9ed612..337d1943af4 100644
--- a/drivers/net/enic/cq_enet_desc.h
+++ b/drivers/net/enic/cq_enet_desc.h
@@ -101,14 +101,18 @@ static inline void cq_enet_rq_desc_dec(struct cq_enet_rq_desc *desc,
u8 *tcp_udp_csum_ok, u8 *udp, u8 *tcp, u8 *ipv4_csum_ok,
u8 *ipv6, u8 *ipv4, u8 *ipv4_fragment, u8 *fcs_ok)
{
- u16 completed_index_flags = le16_to_cpu(desc->completed_index_flags);
- u16 q_number_rss_type_flags =
- le16_to_cpu(desc->q_number_rss_type_flags);
- u16 bytes_written_flags = le16_to_cpu(desc->bytes_written_flags);
+ u16 completed_index_flags;
+ u16 q_number_rss_type_flags;
+ u16 bytes_written_flags;
cq_desc_dec((struct cq_desc *)desc, type,
color, q_number, completed_index);
+ completed_index_flags = le16_to_cpu(desc->completed_index_flags);
+ q_number_rss_type_flags =
+ le16_to_cpu(desc->q_number_rss_type_flags);
+ bytes_written_flags = le16_to_cpu(desc->bytes_written_flags);
+
*ingress_port = (completed_index_flags &
CQ_ENET_RQ_DESC_FLAGS_INGRESS_PORT) ? 1 : 0;
*fcoe = (completed_index_flags & CQ_ENET_RQ_DESC_FLAGS_FCOE) ?