From: boris.brezillon@free-electrons.com (Boris Brezillon)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] dma: sun4i: expose block size and wait cycle configuration to DMA users
Date: Fri, 11 Mar 2016 10:45:52 +0100 [thread overview]
Message-ID: <20160311104552.23e06a16@bbrezillon> (raw)
In-Reply-To: <20160311062607.GP11154@localhost>
On Fri, 11 Mar 2016 11:56:07 +0530
Vinod Koul <vinod.koul@intel.com> wrote:
> On Wed, Mar 09, 2016 at 12:06:27PM +0100, Boris Brezillon wrote:
> > On Tue, 8 Mar 2016 08:25:47 +0530
> > Vinod Koul <vinod.koul@intel.com> wrote:
> > >
> > > Why does dmaengine need to wait? Can you explain that
> >
> > I don't have an answer for that one, but when I set WAIT_CYCLES to 1
> > for the NAND use case it does not work. So I guess it is somehow
> > related to how the DRQ line is controlled on the device side...
>
> Is the WAIT cycle different for different usages or same for all
> usages/channels?
>
In Allwinner BSP they adapt it on a per slave device basis, but since
DMA channels are dynamically allocated, you can't know in advance which
physical channel will be attached to a specific device.
Another option I considered was adding a new cell to the sun4i DT
binding to encode these WAIT_CYCLES and BLOCK_SIZE information. But I'm
not sure adding that to the DT is a good idea (not to mention that it
would break DT ABI again, and given the last discussions on this topic,
I'm not sure it's a good idea :-/).
--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
next prev parent reply other threads:[~2016-03-11 9:45 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-07 9:59 [PATCH] dma: sun4i: expose block size and wait cycle configuration to DMA users Boris Brezillon
2016-03-07 14:54 ` Vinod Koul
2016-03-07 15:08 ` Boris Brezillon
2016-03-07 20:30 ` Maxime Ripard
2016-03-08 2:55 ` Vinod Koul
2016-03-08 2:59 ` Vinod Koul
2016-03-08 7:51 ` Maxime Ripard
2016-03-08 8:42 ` [linux-sunxi] " Hans de Goede
2016-03-08 10:05 ` Vinod Koul
2016-03-09 10:58 ` Maxime Ripard
2016-03-08 8:46 ` Boris Brezillon
2016-03-08 9:10 ` [linux-sunxi] " Priit Laes
2016-03-08 10:04 ` Vinod Koul
2016-03-09 10:08 ` [linux-sunxi] " LABBE Corentin
2016-03-08 9:59 ` Vinod Koul
2016-03-09 10:14 ` Boris Brezillon
2016-03-11 6:24 ` Vinod Koul
2016-03-11 9:40 ` Boris Brezillon
2016-03-11 10:06 ` Vinod Koul
2016-03-11 10:26 ` Boris Brezillon
2016-03-11 11:21 ` Vinod Koul
2016-03-09 11:06 ` Boris Brezillon
2016-03-11 6:26 ` Vinod Koul
2016-03-11 9:45 ` Boris Brezillon [this message]
2016-03-11 10:09 ` Vinod Koul
2016-03-11 10:55 ` Maxime Ripard
2016-03-11 11:18 ` Vinod Koul
2016-03-14 11:46 ` Maxime Ripard
2016-03-16 3:22 ` Vinod Koul
2016-03-07 15:30 ` [linux-sunxi] " Priit Laes
2016-03-07 15:47 ` Boris Brezillon
2016-03-07 17:15 ` Emilio López
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