From: Mark Salter <msalter@redhat.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, ming.lei@canonical.com,
stern@rowland.harvard.edu
Subject: Re: [PATCH 2/3] define ARM-specific dma_coherent_write_sync
Date: Tue, 06 Sep 2011 10:37:15 -0400 [thread overview]
Message-ID: <1315319837.2313.1.camel@deneb.redhat.com> (raw)
In-Reply-To: <CAHkRjk7ZMDQh8sYf7N_4LLS12JU2ps8dkC34gNWNH+-Zp0p8Rg@mail.gmail.com>
On Tue, 2011-09-06 at 15:32 +0100, Catalin Marinas wrote:
> That's what mb() and wmb() do already, at least on ARM. Why do we need
> another API? IIRC from past discussions on linux-arch around barriers,
> the mb() should be sufficient in the case of DMA coherent buffers.
> That's why macros like writel() on ARM have the mb() added by default
> (for cases where you start the DMA transfer by writing to a device
> register).
For USB EHCI, the driver does not necessarily write to a register after
writing to DMA coherent memory. In some cases, the controller polls for
information written by the driver.
--Mark
WARNING: multiple messages have this Message-ID (diff)
From: msalter@redhat.com (Mark Salter)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 2/3] define ARM-specific dma_coherent_write_sync
Date: Tue, 06 Sep 2011 10:37:15 -0400 [thread overview]
Message-ID: <1315319837.2313.1.camel@deneb.redhat.com> (raw)
In-Reply-To: <CAHkRjk7ZMDQh8sYf7N_4LLS12JU2ps8dkC34gNWNH+-Zp0p8Rg@mail.gmail.com>
On Tue, 2011-09-06 at 15:32 +0100, Catalin Marinas wrote:
> That's what mb() and wmb() do already, at least on ARM. Why do we need
> another API? IIRC from past discussions on linux-arch around barriers,
> the mb() should be sufficient in the case of DMA coherent buffers.
> That's why macros like writel() on ARM have the mb() added by default
> (for cases where you start the DMA transfer by writing to a device
> register).
For USB EHCI, the driver does not necessarily write to a register after
writing to DMA coherent memory. In some cases, the controller polls for
information written by the driver.
--Mark
next prev parent reply other threads:[~2011-09-06 14:37 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-31 21:30 [PATCH 0/3] RFC: addition to DMA API Mark Salter
2011-08-31 21:30 ` Mark Salter
2011-08-31 21:30 ` [PATCH 1/3] add dma_coherent_write_sync " Mark Salter
2011-08-31 21:30 ` Mark Salter
2011-09-01 2:59 ` Josh Cartwright
2011-09-01 2:59 ` Josh Cartwright
2011-09-01 9:57 ` Michał Mirosław
2011-09-01 9:57 ` Michał Mirosław
2011-09-01 12:36 ` Mark Salter
2011-09-01 12:36 ` Mark Salter
2011-09-06 14:30 ` Catalin Marinas
2011-09-06 14:30 ` Catalin Marinas
2011-08-31 21:30 ` [PATCH 2/3] define ARM-specific dma_coherent_write_sync Mark Salter
2011-08-31 21:30 ` Mark Salter
2011-09-06 14:32 ` Catalin Marinas
2011-09-06 14:32 ` Catalin Marinas
2011-09-06 14:37 ` Mark Salter [this message]
2011-09-06 14:37 ` Mark Salter
2011-09-06 14:48 ` Catalin Marinas
2011-09-06 14:48 ` Catalin Marinas
2011-09-06 15:02 ` Mark Salter
2011-09-06 15:02 ` Mark Salter
2011-10-03 1:40 ` Jon Masters
2011-10-03 1:40 ` Jon Masters
2011-10-03 8:44 ` Catalin Marinas
2011-10-03 8:44 ` Catalin Marinas
2011-10-03 9:24 ` Jon Masters
2011-10-03 9:24 ` Jon Masters
2011-08-31 21:30 ` [PATCH 3/3] add dma_coherent_write_sync calls to USB EHCI driver Mark Salter
2011-08-31 21:30 ` Mark Salter
2011-09-01 2:33 ` Ming Lei
2011-09-01 2:33 ` Ming Lei
2011-09-01 2:09 ` [PATCH 0/3] RFC: addition to DMA API Ming Lei
2011-09-01 2:09 ` Ming Lei
2011-09-01 3:09 ` Alan Stern
2011-09-01 3:09 ` Alan Stern
2011-09-01 3:41 ` Ming Lei
2011-09-01 3:41 ` Ming Lei
2011-09-01 8:45 ` Will Deacon
2011-09-01 8:45 ` Will Deacon
2011-09-01 9:14 ` Ming Lei
2011-09-01 9:14 ` Ming Lei
2011-09-01 15:42 ` Alan Stern
2011-09-01 15:42 ` Alan Stern
2011-09-01 16:04 ` Russell King - ARM Linux
2011-09-01 16:04 ` Russell King - ARM Linux
2011-09-01 17:31 ` Will Deacon
2011-09-01 17:31 ` Will Deacon
2011-09-01 18:07 ` Russell King - ARM Linux
2011-09-01 18:07 ` Russell King - ARM Linux
2011-09-01 19:14 ` Mark Salter
2011-09-01 19:14 ` Mark Salter
2011-09-01 15:22 ` Alan Stern
2011-09-01 15:22 ` Alan Stern
2011-09-01 15:56 ` Ming Lei
2011-09-01 15:56 ` Ming Lei
2011-09-01 16:48 ` Alan Stern
2011-09-01 16:48 ` Alan Stern
2011-09-02 0:59 ` Ming Lei
2011-09-02 0:59 ` Ming Lei
2011-09-02 13:53 ` Alan Stern
2011-09-02 13:53 ` Alan Stern
2011-09-01 9:11 ` Will Deacon
2011-09-01 9:11 ` Will Deacon
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