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net: stmmac: ensure that the device has released ownership before reading data

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[ 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 <niklas.cassel@axis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Niklas Cassel 2018-02-26 22:47:08 +01:00 committed by Greg Kroah-Hartman
parent cecf8a6904
commit 82aad32b4a
1 changed files with 5 additions and 0 deletions
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5
drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
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@ -1343,6 +1343,11 @@ static void stmmac_tx_clean(struct stmmac_priv *priv)
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 */