Hi Jeff, For several times I tried libata on small machines equipped with either CompactFlash or IDE DOM (Disk-On-Module). All those machines with small flashes (<= 256 MB) were about 35-40% slower under libata than under the plain old IDE driver. I realized that all the slower ones were running PIO only.
Today I had time to investigate the issue on a Geode LX board. At first I thought it was the pata_cs5536 driver which would have incorrect timings, but this was not the case. I finally noticed that under IDE, my flashes were running in 32-bit mode while I could not enable 32-bit with libata. Reading ata_data_xfer() made it obvious that transfers were only 16-bit wide. Thus, I have implemented the 32-bit mode to bring the performance back to the level of the old IDE driver. I jumped from 1.5 MB/s to 2.5 MB/s, which is an important difference at this level of performance, especially when large files are read. The 32-bit mode is enabled using the ioctl which is already implemented but only accepts a null value. I'm joining two patches which I hope you'll consider for inclusion. I've updated them to latest Linus' git. Best regards, Willy - To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
