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Date: Wed, 11 Nov 2015 02:36:43 +0200 From: Andy Shevchenko <andy.shevchenko@...il.com> To: Måns Rullgård <mans@...sr.com> Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, netdev <netdev@...r.kernel.org>, slash.tmp@...e.fr Subject: Re: [PATCH v5] net: ethernet: add driver for Aurora VLSI NB8800 Ethernet controller On Wed, Nov 11, 2015 at 1:07 AM, Måns Rullgård <mans@...sr.com> wrote: > Andy Shevchenko <andy.shevchenko@...il.com> writes: >>>>> + nb8800_writel(priv, NB8800_TX_DESC_ADDR, txb->dma_desc); >>>>> + wmb(); /* ensure desc addr is written before starting DMA */ >>>> >>>> Hm… Have I missed corresponding rmb() ? If it's about MMIO, perhaps mmiowb() ? >>> >>> Possibly. >> >> Standalone wmb() doesn't make sense. > > It does if you need to enforce ordering between normal and I/O memory. > In fact, since the descriptor is filled in using normal memory accesses, > my understanding is that mmiowb() would be insufficient here. The > comment could be improved, however. Can you then explain what exactly you are assured against in all cases where you are using wmb()s? It seems I don't recognize this part in some excerpts. -- With Best Regards, Andy Shevchenko -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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