linux-kernel - Re: [EXT] [PATCH net] net: mvneta: fix the Rx desc buffer DMA unmapping

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Message-ID: <87k1ngjjtd.fsf@bootlin.com>
Date:   Thu, 20 Sep 2018 16:59:58 +0200
From:   Gregory CLEMENT <gregory.clement@...tlin.com>
To:     Antoine Tenart <antoine.tenart@...tlin.com>
Cc:     Yelena Krivosheev <yelena@...vell.com>,
        "davem\@davemloft.net" <davem@...emloft.net>,
        "netdev\@vger.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        "thomas.petazzoni\@bootlin.com" <thomas.petazzoni@...tlin.com>,
        "maxime.chevallier\@bootlin.com" <maxime.chevallier@...tlin.com>,
        "miquel.raynal\@bootlin.com" <miquel.raynal@...tlin.com>,
        Nadav Haklai <nadavh@...vell.com>,
        Stefan Chulski <stefanc@...vell.com>,
        Yan Markman <ymarkman@...vell.com>,
        "mw\@semihalf.com" <mw@...ihalf.com>
Subject: Re: [EXT] [PATCH net] net: mvneta: fix the Rx desc buffer DMA unmapping

Hi Antoine,
 
 On jeu., sept. 20 2018, Antoine Tenart <antoine.tenart@...tlin.com> wrote:

> Hi Yelena,
>
> On Thu, Sep 20, 2018 at 10:14:56AM +0000, Yelena Krivosheev wrote:
>> 
>> Please, check and fix all cases of dma_unmap_single() usage.
>> See mvneta_rxq_drop_pkts()
>> ...
>> 		if (!data || !(rx_desc->buf_phys_addr))
>> 			continue;
>> 		dma_unmap_single(pp->dev->dev.parent, rx_desc->buf_phys_addr,
>> 				 MVNETA_RX_BUF_SIZE(pp->pkt_size), DMA_FROM_DEVICE);
>> 		__free_page(data);
>> ...
>
> I had a look at the one reported by CONFIG_DMA_API_DEBUG, and at DMA
> unmapping calls using PAGE_SIZE. As you pointed out there might be
> others parts, thanks!

Actually Jisheng had submitted a similar patch few weeks ago and as I
pointed at this time, the dma_unmap in mvneta_rxq_drop_pkts can be
called when the allocation is done in with HWBM in this case which use a
dma_map_single.

I though that in this case using dma_map_single is the things to do even
if in the SWBM case it is less optimal.

Gregory

>
> Antoine
>
> -- 
> Antoine Ténart, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com

-- 
Gregory Clement, Bootlin
Embedded Linux and Kernel engineering
http://bootlin.com