From a3d4c34cdea992e137bed4cf66c03e2db6a324ec Mon Sep 17 00:00:00 2001 From: Niklas Cassel Date: Mon, 26 Feb 2018 22:47:08 +0100 Subject: net: stmmac: ensure that the device has released ownership before reading data [ Upstream commit a6b25da5e7ba212af5826a662e6a035a79bffabd ] 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 Signed-off-by: David S. Miller Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- 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 d0cc73795056..40ae1be372cc 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c @@ -1829,6 +1829,11 @@ 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 */ -- cgit v1.2.3