From: Leon Woestenberg <leon.woestenberg@gmail.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: arnd@arndb.de, linux-kernel@vger.kernel.org,
FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>,
scottwood@freescale.com, chris.pringle@oxtel.com,
linuxppc-dev@lists.ozlabs.org
Subject: Re: PowerPC PCI DMA issues (prefetch/coherency?)
Date: Wed, 17 Jun 2009 03:13:07 +0200 [thread overview]
Message-ID: <c384c5ea0906161813v26b3a739h8ce36e395841df35@mail.gmail.com> (raw)
In-Reply-To: <1245200912.21602.2.camel@pasglop>
Hello Benjamin,
On Wed, Jun 17, 2009 at 3:08 AM, Benjamin
Herrenschmidt<benh@kernel.crashing.org> wrote:
> On Wed, 2009-06-17 at 02:56 +0200, Leon Woestenberg wrote:
>> I use pci_map_sg(), have the device perform either DMA master reads or
>> writes to the bus address using PCIe.
>> After that, I use pci_unmap_sg().
>>
>> My assumption is that pci_unmap_sg() either makes the cache coherent
>> or invalidated and thus I do not need to take further actions.
>> This is on a MPC83xx or 85xx system.
>>
>> Is this assumption correct?
>
> It is, as far as I understand things :-) Those APIs are fun.
>
> You should only need the explicit sync calls if you are going to peek or
> poke at the DMA mapped memory before you unmap it.
>
Thanks, then at least I understand things in the corr^H^H^H^Hsame way :-)
And btw, I hadn't seen any data mismatch yet.
Regards,
--
Leon 'likewise' Woestenberg
next prev parent reply other threads:[~2009-06-17 1:13 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <4A37A503.3030209@oxtel.com>
[not found] ` <20090616162114.GA5051@loki.buserror.net>
[not found] ` <4A37C97A.5050508@oxtel.com>
2009-06-16 16:46 ` PowerPC PCI DMA issues (prefetch/coherency?) Scott Wood
2009-06-16 16:57 ` Chris Pringle
2009-06-16 17:03 ` Scott Wood
2009-06-16 17:43 ` Arnd Bergmann
2009-06-16 17:49 ` Scott Wood
2009-06-16 18:02 ` Arnd Bergmann
2009-06-17 0:18 ` Benjamin Herrenschmidt
2009-06-17 0:37 ` FUJITA Tomonori
2009-06-17 0:56 ` Leon Woestenberg
2009-06-17 1:08 ` Benjamin Herrenschmidt
2009-06-17 1:13 ` Leon Woestenberg [this message]
2009-06-17 1:07 ` Benjamin Herrenschmidt
2009-06-17 7:58 ` Chris Pringle
2009-06-17 13:18 ` Chris Pringle
2009-06-18 11:24 ` Chris Pringle
2009-06-22 14:31 ` AW: " Sergej.Stepanov
2009-06-29 8:11 ` Chris Pringle
2009-06-16 14:08 Chris Pringle
2009-06-16 15:48 ` Roderick Colenbrander
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