On Tue, Mar 1, 2011 at 7:48 PM, Kushal Koolwal <kushalkoolwal@xxxxxxxxx> wrote: >> You shouldn't really use a 40-conductor cable in a system that has devices >> that support faster than UDMA mode 2. > The system restrict device speeds up to UMDA2 speeds at the firmware > level (BIOS) and physical connectors use to connect IDE devices comes > only in 40 conductor cable format. > >> Normally the kernel would detect the >> 40-wire cable and block using faster speeds, but it seems like the pata_sch >> driver doesn't support cable detection as the cable_detect method is set to >> ata_cable_unknown (either because the hardware doesn't support it or the >> author didn't bother to implement it), so it can't detect this >> automatically. > Yes you are right. We have another system with same UDMA2 restrictions > (BIOS/Physical connectors) but uses the piix driver (instead of > pata_sch) and in that we don't see these messages. > > I don't know much about how the Linux IDE sub-system works but I am > willing to test and report the results if somebody cares to write a > patch that introduces the cable detection mechanism in the pata_sch > driver. Reading through the SCH datasheet (http://download.intel.com/design/chipsets/embedded/datashts/319537.pdf) I don't see any mention of a mechanism which can be used to detect the cable. In some cases device-side cable detection can be done but I don't know that all devices support it. So there might not actually be a way to do it on this controller. -- 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
