Does s3cmci driver support DMA data transfer?
laforge at openmoko.org
Fri Jan 11 22:42:42 CET 2008
On Wed, Jan 09, 2008 at 10:16:01PM +0800, Lonsn wrote:
> I'm now using s3cmci patch(http://svnweb.openmoko.org/branches/src/target/kernel/2.6.21.x/patches/s3c_mci.patch?rev=2805&view=auto) and it works well. The SD card write speed is about 26Mbits/s(S3C2440A 400MHz, Sandisk UltraIII 2GB sd card).
> But the CPU load is too heavy(80%). So I want to let s3cmci driver work in DMA mode. I changed host->dodma = 1;
> But it doesn't work and the driver cann't detect the sd card. Does
> anyone use the s3cmci driver in DMA mode successfully?
I don't think anyone has used it with DMA in a long time (probably no
later than 2.6.14 or even 2.6.10). There have been DMA API changes that
might not be reflected in the driver.
I strongly recommend you use the driver that is present in the 2.6.24.x
branch of the openmoko svn (which is also what has been submitted to
linux-arm-kernel some weeks back).
> Another question: Can sd card work speed be more than 25MHz? As I
> know, the maximum sdi clock of S3C2440A is 33MHz(APB clock=67MHz,
> prescaler value=1) and UltraIII sd card can support 40MHz
> frequency(20MBytes/s). If we can let s3cmci driver works in 33MHz
> modes, maybe the sd card IO performance could be increased a lot. But
> the sdi clock works only 22.5MHz(prescaler value=2) mode now.
I don't think anyone has tried this yet.
- Harald Welte <laforge at openmoko.org> http://openmoko.org/
Software for the world's first truly open Free Software mobile phone
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