From: Jakub Kicinski <kuba@kernel.org>
To: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "Måns Rullgård" <mans@mansr.com>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
"Dan Malek" <dan@embeddededge.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Eric Dumazet" <edumazet@google.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"Vitaly Bordug" <vbordug@ru.mvista.com>,
"Paolo Abeni" <pabeni@redhat.com>,
"Joakim Tjernlund" <joakim.tjernlund@lumentis.se>,
"David S. Miller" <davem@davemloft.net>
Subject: Re: [PATCH] net: fs_enet: sync rx dma buffer before reading
Date: Sat, 21 May 2022 10:44:30 -0700 [thread overview]
Message-ID: <20220521104430.1212bed5@kernel.org> (raw)
In-Reply-To: <d8cc1123-30d2-d65b-84b1-2ffee0d50aab@csgroup.eu>
On Sat, 21 May 2022 06:44:41 +0000 Christophe Leroy wrote:
> > Hm, I think the patch is necessary, sorry if you're also saying that
> > and I'm misinterpreting.
>
> Well, I say the contrary.
>
> On the mainline the patch may be applied as is, it won't harm.
>
> However, it is gets applied to kernel 4.9 (based on the fixes: tag), it
> will break the driver for at least powerpc 8xx.
I see, we should make a note of that in the commit message so it doesn't
get sucked into stable.
> > Without the dma_sync_single_for_cpu() if swiotlb is used the data
> > will not be copied back into the original buffer if there is no sync.
>
> I don't know how SWIOTLB works or even what it is, does any of the
> microcontrollers embedding freescale ethernet uses that at all ?
AFAIU SWIOTLB basically forces the use of bounce buffers even if the
device can reach the entire DRAM. I think some people also use it for
added security? IDK. I mostly use it to check if I'm using the DMA API
"right" :)
WARNING: multiple messages have this Message-ID (diff)
From: Jakub Kicinski <kuba@kernel.org>
To: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "Måns Rullgård" <mans@mansr.com>,
"Pantelis Antoniou" <pantelis.antoniou@gmail.com>,
"David S. Miller" <davem@davemloft.net>,
"Eric Dumazet" <edumazet@google.com>,
"Paolo Abeni" <pabeni@redhat.com>,
"Vitaly Bordug" <vbordug@ru.mvista.com>,
"Dan Malek" <dan@embeddededge.com>,
"Joakim Tjernlund" <joakim.tjernlund@lumentis.se>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] net: fs_enet: sync rx dma buffer before reading
Date: Sat, 21 May 2022 10:44:30 -0700 [thread overview]
Message-ID: <20220521104430.1212bed5@kernel.org> (raw)
In-Reply-To: <d8cc1123-30d2-d65b-84b1-2ffee0d50aab@csgroup.eu>
On Sat, 21 May 2022 06:44:41 +0000 Christophe Leroy wrote:
> > Hm, I think the patch is necessary, sorry if you're also saying that
> > and I'm misinterpreting.
>
> Well, I say the contrary.
>
> On the mainline the patch may be applied as is, it won't harm.
>
> However, it is gets applied to kernel 4.9 (based on the fixes: tag), it
> will break the driver for at least powerpc 8xx.
I see, we should make a note of that in the commit message so it doesn't
get sucked into stable.
> > Without the dma_sync_single_for_cpu() if swiotlb is used the data
> > will not be copied back into the original buffer if there is no sync.
>
> I don't know how SWIOTLB works or even what it is, does any of the
> microcontrollers embedding freescale ethernet uses that at all ?
AFAIU SWIOTLB basically forces the use of bounce buffers even if the
device can reach the entire DRAM. I think some people also use it for
added security? IDK. I mostly use it to check if I'm using the DMA API
"right" :)
next prev parent reply other threads:[~2022-05-21 17:45 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-19 19:24 [PATCH] net: fs_enet: sync rx dma buffer before reading Mans Rullgard
2022-05-20 5:39 ` Christophe Leroy
2022-05-20 12:35 ` Måns Rullgård
2022-05-20 12:35 ` Måns Rullgård
2022-05-20 12:54 ` Christophe Leroy
2022-05-20 12:54 ` Christophe Leroy
2022-05-20 17:43 ` Jakub Kicinski
2022-05-20 17:43 ` Jakub Kicinski
2022-05-21 6:44 ` Christophe Leroy
2022-05-21 6:44 ` Christophe Leroy
2022-05-21 17:44 ` Jakub Kicinski [this message]
2022-05-21 17:44 ` Jakub Kicinski
2022-05-23 20:23 ` Jakub Kicinski
2022-05-23 20:23 ` Jakub Kicinski
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