From 0701fb553c11d6606e32e26ab79ea9cca18db8da Mon Sep 17 00:00:00 2001
From: Niklas Cassel <niklas.cassel@axis.com>
Date: Mon, 26 Feb 2018 22:47:08 +0100
Subject: [PATCH 3/6] net: stmmac: ensure that the device has released
ownership before reading data
Git-commit: a6b25da5e7ba212af5826a662e6a035a79bffabd
Patch-mainline: v4.17-rc1
References: git-fixes
According to Documentation/memory-barriers.txt, we need to use a
dma_rmb() after reading the status/own bit, to ensure that all
descriptor fields are read after reading the own bit.
This way, we ensure that the DMA engine is done with the DMA
descriptor before we read the other descriptor fields, e.g. reading
the tx hardware timestamp (if PTP is enabled).
Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Denis Kirjanov <denis.kirjanov@suse.com>
---
drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index a4b578a5f72b..15a5cf5ac38a 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -1851,6 +1851,11 @@ static void stmmac_tx_clean(struct stmmac_priv *priv, u32 queue)
if (unlikely(status & tx_dma_own))
break;
+ /* Make sure descriptor fields are read after reading
+ * the own bit.
+ */
+ dma_rmb();
+
/* Just consider the last segment and ...*/
if (likely(!(status & tx_not_ls))) {
/* ... verify the status error condition */
--
2.16.4