On Mon, 2005-07-25 at 10:30 +0200, Hannes Reinecke wrote: > it appears that the fallback sequence in > scsi_transport_spi.c:spi_dv_retrain() > is somewhat incorrect. > > According to SPI-3 (spi3r14, actually), the flags DT, IU, and QAS can be > set in the following order of precedence (Table 55, p 155): > - DT > - IU > - QAS Actually, this is superceded by spi4 and 5. QAS is now optional for any transfer agreement. > However, the fallback routine in spi_dv_retrain first unsets IU, _then_ > QAS, and ignoring DT entirely. This smells a bit fishy. > Any reasons for this? DT is theoretically a more stable transfer mechanism in the face of line noise than ST, so if the drive supports it, it makes some sense to back down the periods still retaining DT if possible. DT also mandates data group transfers if IU isn't mandated, so it's a safer protocol at detecting errors as well. James - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
