Hello, The current EH speed down code is more of a feature demonstration and goes through rdiculously many meaningless steps when condition is met. This patchset tries to put some intelligence into speed down sequence. The goal is to achieve reasonable number of speed down steps reasonably spaced from one another and consider NCQ, cable type and the current protocol when determining speed down steps, while not bloating the code too much with nitty gritty details. Roughly, the rules are... 1. If NCQ and protocol/timeout/unknown dev errors occur, turn off NCQ 2. If excessive transfer errors occur, speed down within the current transfer mode (UDMA/MWDMA/PIO). If UDMA, it's first adjusted down a step, if error conditions persist, 40c limit is applied. Speed down is done only twice. 3. If PATA && used up all DMA speed down steps && a LOT of transmission/unknown errors occur, switch to PIO. So, we never automatically step down to PIO on SATA. This is intended. Some SATA hdd even seems to have problem with PIO data transfer commands. The last patch makes ahci report HSM violation error on spurious completion of NCQ commands, thus causing NCQ off after several such incidents. These drives should be blacklisted for DMA eventually. This patchset is against... upstream (eb0e63cca36a3389f0ccab4584f6d479b983fad5) + [1] pata_platform-fix-devres-conversion + [2] libata-convert-to-iomap Ric, I guess this resolves the to-do item from you which has been sitting in my mailbox for way too long. What do you think about the rules? Thanks. -- tejun [1] http://article.gmane.org/gmane.linux.kernel/488509 [2] hmm.. can't find it any archive. Might have been ignored due to size. Jeff, did you receive it? - To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
