WLAN from SDIO to SPI: sneak preview
werner at openmoko.org
Thu Sep 4 10:17:56 CEST 2008
The MMC-SPI version using the bit-banging GPIO driver is now working
reasonably well. I put a sneak preview here:
This is the slowest of all the possible stack combinations, so it has
more academic value than anything else.
Some performance data:
- ping -c 25 to my WRT54G
25 packets transmitted, 24 packets received, 4% packet loss
round-trip min/avg/max = 26.147/211.685/685.817 ms
- an SCP of the kernel from a PC connected via the WRT54G:
uImage 100% 1678KB 19.5KB/s 01:26
The throughput is actually better than I expected ;-) The ping
latency came as a surprise, though. However, when I look at what
the competition is doing (the original stack):
- ping -c 25:
25 packets transmitted, 25 packets received, 0% packet loss
round-trip min/avg/max = 16.972/150.415/452.088 ms
- same SCP:
uImage 100% 1678KB 88.3KB/s 00:19
That should be a lot better - my driver only gets a clock of about
300kHz while burning 90% CPU in spi_s3c24xx_gpio, while the S3C SDIO
driver goes 25MHz and has a 4 bit bus to start with.
So it seems that my GTA02 isn't quite happy with the WLAN in general.
Might be because all its shields are off ...
Next: try the accelerated SPI driver.
More information about the openmoko-kernel