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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Leon Woestenberg <leon.woestenberg@gmail.com>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>,
	arnd@arndb.de, scottwood@freescale.com, chris.pringle@oxtel.com,
	linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: PowerPC PCI DMA issues (prefetch/coherency?)
Date: Wed, 17 Jun 2009 11:08:32 +1000	[thread overview]
Message-ID: <1245200912.21602.2.camel@pasglop> (raw)
In-Reply-To: <c384c5ea0906161756j4b701abfj2a8908b9c93ddd04@mail.gmail.com>

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.

Cheers,
Ben.





WARNING: multiple messages have this Message-ID (diff)
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Leon Woestenberg <leon.woestenberg@gmail.com>
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 11:08:32 +1000	[thread overview]
Message-ID: <1245200912.21602.2.camel@pasglop> (raw)
In-Reply-To: <c384c5ea0906161756j4b701abfj2a8908b9c93ddd04@mail.gmail.com>

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.

Cheers,
Ben.

  reply	other threads:[~2009-06-17  1:11 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-06-16 13:58 PowerPC PCI DMA issues (prefetch/coherency?) Chris Pringle
2009-06-16 14:16 ` Michael S. Zick
2009-06-16 14:59 ` Hu Gang
2009-06-16 16:21 ` Scott Wood
2009-06-16 16:34   ` Chris Pringle
2009-06-16 16:46     ` Scott Wood
2009-06-16 16:46       ` Scott Wood
2009-06-16 16:57       ` Chris Pringle
2009-06-16 16:57         ` Chris Pringle
2009-06-16 17:03         ` Scott Wood
2009-06-16 17:03           ` Scott Wood
2009-06-16 17:43           ` Arnd Bergmann
2009-06-16 17:49             ` Scott Wood
2009-06-16 17:49               ` Scott Wood
2009-06-16 18:02               ` Arnd Bergmann
2009-06-16 18:02                 ` Arnd Bergmann
2009-06-17  0:18                 ` Benjamin Herrenschmidt
2009-06-17  0:37                   ` FUJITA Tomonori
2009-06-17  0:37                     ` FUJITA Tomonori
2009-06-17  0:56                     ` Leon Woestenberg
2009-06-17  0:56                       ` Leon Woestenberg
2009-06-17  1:08                       ` Benjamin Herrenschmidt [this message]
2009-06-17  1:08                         ` Benjamin Herrenschmidt
2009-06-17  1:13                         ` Leon Woestenberg
2009-06-17  1:13                           ` Leon Woestenberg
2009-06-17  1:07                     ` Benjamin Herrenschmidt
2009-06-17  1:07                       ` Benjamin Herrenschmidt
2009-06-17  7:58           ` Chris Pringle
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
2009-06-22 14:31                   ` 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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