Am Donnerstag, 6. Mai 2010 15:59:44 schrieb Wolfgang Wegner: > Hi Alexander, > > On Thu, May 06, 2010 at 03:33:53PM +0200, Alexander Stein wrote: > [...] > > > IIRC 400kBytes/second is the initial speed for SD cards on SPI. The card > > itself responds which max speed it can handle. Which could be adjusted > > later (up to 25MHz or even more). > > the initial speed is 400 kBits/second, because there may be some (few) > cards that could not handle more.
Yep, it's need to distinguish between SD and MMC. IIRC that's also the speed a MMC can handle (at maximum?). > > I backported this spi_mmc driver to 2.6.10 (yes, even older) and it is > > slow, nevertheless. I don't know how SPI is done in u-boot, but maybe > > the system interrupts in linux like ethernet and timer slow SPI transfer > > down. > > Thanks for the confirmation! e.g. If I'm downloading something per FTP to the SD card I get a big burst at first and then several seconds 0bytes/s In this case I also detected a bug in the windows TCP stack if some packets get dropped... On a new AT91 board with integrated MCI interface it's much faster > I just found a page from the blackfin linux project: > http://docs.blackfin.uclinux.org/doku.php?id=linux-kernel:drivers:spi_mmc > which suggests better values (using dd with bs=512 should be similar to > what bonnie does in the block tests?). A hint I got from this page was to > disable SPI DMA (which was also enabled on my coldfire), and this improved > the situation to get around 115 kBytes/second. I can't say much about actual transfer rates. But i noticed a real slowdown when the filesystem buffer is about to be flushed. We are using a COldfire 5484 and AFAIK there is no DMA for SPI, at least we don't use it. Best regards Alexander _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
