2008-09-12 22:28:59     About SD_MMC and CF TRUE IDE on BF531

2008-09-12 22:28:59     About SD_MMC and CF TRUE IDE on BF531

Pei Chen (CHINA)

Message: 62091   

Hi,

I am working on a data recording project on a custom BF531 board( built by myself).

I have two questions here:

1 the reading speed of SD card is about 550KB/s while the writing speed is only 270KB/s, for a fat system is it OK?

I just followed the instructions in : http://docs.blackfin.uclinux.org/doku.php?id=linux-kernel:drivers:spi_mmc&s[]=mmc

and do the speed measurement using command: time.(without cache)

2 I don't know where the true-ide mode CF card driver is, I want to know whether the information belowed is still up to date.

:http://docs.blackfin.uclinux.org/doku.php?id=linux-kernel:drivers:bfin_cf_pcmcia

Thank you!

Chen Pei

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2008-09-13 16:11:34     Re: About SD_MMC and CF TRUE IDE on BF531

Mike Frysinger (UNITED STATES)

Message: 62132   

i dont think we've done speed tests on the mmc/sd interface over SPI

the CF IDE doc you refer to is up to date

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2008-09-14 18:20:25     Re: About SD_MMC and CF TRUE IDE on BF531

Ian Jeffray (UNITED KINGDOM)

Message: 62138   

Hi Chen,

Your data rates seem a little slow to me.   It will depend on the SD card you're using, but I've had read and write rates of around 900KB/sec on a BF537-STAMP with the Rubico MMC reader, but I've seen forum postings here suggesting rates over 2MB/sec are achievable.   This performance is something I'm going to be looking at a little more closely in the next few weeks.

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2008-09-15 00:48:06     Re: About SD_MMC and CF TRUE IDE on BF531

crystal shark (CHINA)

Message: 62144   

hi Jeffray,

                  do you add the  "-o sync" when you mount the spi_mmc card?

                  In our test , if we

                         mount  /dev/spi_mmc /mnt -t vfat

                         I've had read  rates of around 900KB/sec.

                  But if we use the command below:

                         mount  /dev/spi_mmc /mnt -t vfat  -o sync

                           I've had read  rates of around 470KB/sec.

                    and the write rates is slower than the read rates!

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2008-09-15 02:01:51     Re: About SD_MMC and CF TRUE IDE on BF531

Mike Frysinger (UNITED STATES)

Message: 62146   

so why exactly are you surprised that using the sync mount option results in lower throughput ?

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2008-09-20 11:10:28     Re: About SD_MMC and CF TRUE IDE on BF531

Pei Chen (CHINA)

Message: 62478   

I don't know, why SD accessing speed in our 531 board is too slow, may be the l1 cache and clock speed limit the protocol processing performance. We need a faster data recording solution, but the cf card's true IDE mode' driver can't be compiled in 2005r1.5 now, we are still working on it.

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2008-09-30 11:37:53     Re: About SD_MMC and CF TRUE IDE on BF531

Steve Strobel (UNITED STATES)

Message: 62937   

I haven't gone back and done enough testing to confirm it, but it seemed at one time that the SD transfer rate was greatly affected by the processor load, while the transfer rate to a USB flash drive was not.  Might be another thing to check if you still aren't getting the expected transfer rate.

Steve