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SubjectRe: [PATCH net-next] net: stmmac: remove superfluous wmb() memory barriers
From: Niklas Cassel <>
Date: Thu, 8 Mar 2018 11:30:05 +0100

> These wmb() memory barriers are performed after the last descriptor write,
> and they are followed by enable_dma_transmission()/set_tx_tail_ptr(),
> i.e. a writel() to MMIO register space.
> Since writel() itself performs the equivalent of a wmb() before doing the
> actual write, these barriers are superfluous, and removing them should
> thus not change any existing behavior.
> Ordering within the descriptor writes is already ensured with dma_wmb()
> barriers inside prepare_tx_desc(first, ..)/prepare_tso_tx_desc(first, ..).
> Signed-off-by: Niklas Cassel <>

Please allow me some time to consider this issue a little bit more
before applying this patch.

Thank you Niklas.

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