Hi Simon, On Wed, Jan 19, 2011 at 9:09 AM, Simon Horman <horms@xxxxxxxxxxxx> wrote: > Hi, > > I am currently interested in the read performance of the SDHI driver. I > ran the following tests on a Mackerel board using Linus's latest tree > (6845a44a), which I believe has all of the outstanding patches from Arnd > and Guennadi merged. Nice, thanks for testing this. > I have made the following crude performance measurements using > several different cards. > > dd if=/dev/mmcblk1 of=/dev/null bs=512 count=100000 > > SD1.1: 7.0 MB/s > SD2.0: 7.0 MB/s > SDHC Class 2: 7.1 MB/s > SDHC Class 10: 7.2 MB/s > > Whereas I would expect something like: > > SD1.1 card: 12 MB/s > SD2.0 card: 24 MB/s > SDHC Class 2: 24 MB/s > SDHC Class 10: Faster? Please have a look at the clock frequency set by the SDHI MFD driver (hclk), together with the tmio-mmc settings in tmio_mmc_set_clock(). For the clock to be bumped up properly some capability/feature flags may be needed: MMC_CAP_MMC_HIGHSPEED MMC_CAP_SD_HIGHSPEED Not sure if they are set properly. Probably not. > Possibly relevant portions of my .config are: > > CONFIG_MFD_SH_MOBILE_SDHI=y > CONFIG_TMIO_MMC_DMA=y > CONFIG_MMC_TMIO=y These two are also relevant: CONFIG_SH_DMAE=y CONFIG_DMA_ENGINE=y DMA controller platform data is also needed, not sure the state of your board. You can check out the counters in /proc/interrupts to see if the DMA controller is active or not. Cheers, / magnus -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
