libata: implement 32-bit transfers for PIO mode
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- v1 Latest2 patches 5 repliesIn review
Patches in v1 No applies recorded yet
| # | Subject and files | Size | Replies | Applied |
|---|---|---|---|---|
| 1/2 | libata: implement ATA_IOC_GET_IO32/ATA_IOC_SET_IO32 ioctlsdrivers/ include/ | +63 | 3 replies | |
| 2/2 | libata: implement support for 32-bit PIO transfersdrivers/ | +32 | 1 reply |
Reviews trailers per patch
All 2 patches have a Reviewed-by or Acked-by.
| Patch | Alan Cox |
|---|---|
| 1/2 | A-b |
| 2/2 | A-b |
Trailers given in replies are filled; those carried in the patches from earlier versions are outlined with dashes.
Cover letter [PATCH 0/2] libata: implement 32-bit transfers for PIO mode
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