From: Francois Romieu <romieu@fr.zoreil.com>
To: Pavel Machek <pavel@ucw.cz>
Cc: Lino Sanfilippo <LinoSanfilippo@gmx.de>,
bh74.an@samsung.com, ks.giri@samsung.com,
vipul.pandya@samsung.com, peppe.cavallaro@st.com,
alexandre.torgue@st.com, davem@davemloft.net,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock
Date: Tue, 20 Dec 2016 01:05:32 +0100 [thread overview]
Message-ID: <20161220000531.GA7851@electric-eye.fr.zoreil.com> (raw)
In-Reply-To: <20161219100215.GA6296@amd>
Pavel Machek <pavel@ucw.cz> :
[...]
> Considering the memory barriers... is something like this neccessary
> in the via-rhine ?
Yes.
> AFAICT... we need a barrier after making sure that descriptor is no
> longer owned by DMA (to make sure we don't get stale data in rest of
> descriptor)... and we need a barrier before giving the descriptor to
> the dma, to make sure DMA engine sees the complete update....?
I would not expect stale data while processing a single transmit
descriptor as the transmit completion does not use the rest of the
descriptor at all in the via-rhine driver. However I agree that transmit
descriptors should be read by the cpu with adequate ordering so the
dma_rmb() should stay.
Same kind of narrative for dma_wmb rhine_rx (s/read/written/ and
s/cpu/device/).
> diff --git a/drivers/net/ethernet/via/via-rhine.c b/drivers/net/ethernet/via/via-rhine.c
> index ba5c542..3806e72 100644
> --- a/drivers/net/ethernet/via/via-rhine.c
> +++ b/drivers/net/ethernet/via/via-rhine.c
[...]
> @@ -2061,6 +2062,7 @@ static int rhine_rx(struct net_device *dev, int limit)
>
> if (desc_status & DescOwn)
> break;
> + dma_rmb();
>
I agree with your explanation for this one (late vlan processing in a
different word from the same descriptor).
--
Ueimor
next prev parent reply other threads:[~2016-12-20 0:05 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-07 20:05 Remove private locks to avoid possible deadlock Lino Sanfilippo
2016-12-07 20:05 ` [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock Lino Sanfilippo
2016-12-07 23:15 ` Francois Romieu
2016-12-08 20:32 ` Lino Sanfilippo
2016-12-08 21:54 ` Pavel Machek
2016-12-08 22:12 ` Lino Sanfilippo
2016-12-08 22:18 ` Pavel Machek
2016-12-08 22:45 ` Lino Sanfilippo
2016-12-08 23:19 ` Francois Romieu
2016-12-09 11:21 ` Pavel Machek
2016-12-10 2:25 ` Lino Sanfilippo
2016-12-11 20:11 ` Pavel Machek
2016-12-15 19:27 ` Lino Sanfilippo
2016-12-15 21:03 ` Pavel Machek
2016-12-15 21:32 ` Lino Sanfilippo
2016-12-15 22:33 ` Lino Sanfilippo
2016-12-17 17:31 ` Pavel Machek
2016-12-18 0:15 ` Francois Romieu
2016-12-18 16:15 ` Lino Sanfilippo
2016-12-18 17:23 ` Pavel Machek
2016-12-18 18:30 ` Pavel Machek
2016-12-19 22:49 ` Lino Sanfilippo
2016-12-18 20:16 ` Pavel Machek
2016-12-19 10:02 ` Pavel Machek
2016-12-20 0:05 ` Francois Romieu [this message]
2016-12-07 20:05 ` [PATCH 2/2] net: ethernet: stmmac: " Lino Sanfilippo
2016-12-07 20:55 ` Pavel Machek
2016-12-07 20:59 ` Pavel Machek
2016-12-07 21:37 ` Pavel Machek
2016-12-07 21:43 ` Lino Sanfilippo
2016-12-07 22:34 ` Lino Sanfilippo
2016-12-07 23:21 ` Pavel Machek
2016-12-07 23:41 ` David Miller
2016-12-08 14:08 ` Pavel Machek
2016-12-08 15:26 ` David Miller
2016-12-08 15:46 ` Pavel Machek
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