Re: [PATCH net-next] net: stmmac: remove superfluous wmb() memory barriers

[David Miller]

From: Niklas Cassel <niklas.cassel@xxxxxxxx>
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 <niklas.cassel@xxxxxxxx>

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

Thank you Niklas.