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. > 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! 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. Strange enough enabling DMA decreases performance, there still seems to be room for improvement. I will try to see if I can spot differences in the blackfin kernel that I could back-port - although I already saw there are many differences when back-porting the locking part. Best regards, Wolfgang _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot