Hi, On Thu, Dec 12, 2013 at 12:29 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Thursday 12 December 2013, Douglas Gilbert wrote: >> > >> >> +- apm,tx-speed : Tx operating speed. One set of 3-tuple for >> >> + Gen1 (0x1), Gen2 (0x3), and Gen3 (0x7). Default is >> >> + 0x7. >> > >> > I'm completely confused by this description. Can you rephrase this? >> > It sounds like the only possible values are <1 3 7> for this property. >> >> Most likely Gen1, Gen2 and Gen3 are SATA-speak corresponding to SAS's >> G1, G2 and G3: >> >> G1 Gen1 1.5 Gbps >> G2 Gen2 3 Gbps >> G3 Gen3 6 Gbps >> G4 - 12 Gbps >> G5 - 24 Gbps >> >> And the "7" corresponding to Gen3 is indicating backward compatibility >> with Gen2 and Gen1. The SAS-3 draft only requires backward compatibility >> two generations. Thus you can buy a SAS 12 Gbps HBA today that will >> not support the original SATA 1.5 Gbps class of disks. The corresponding >> value would be 0xe (rather than 0xf) using the tx-speed convention above. >> >> >> My explanation is a bit long winded to put in a device-tree bindings >> file. "RTFM: SATA drafts." should suffice. >> >> >> BTW Compared to some device-tree binding explanations I have had >> to wade through, the above looks pretty good. >> > > Well, the problem is that this is not a SATA device but a PHY device > that happens to support SATA among its protocols (at least PCIe > as well, possibly more but I don't have the specs). The binding > document has to cover all the possibilities or allow extensions > for the other protocols to be implemented later. Having the driver > support SATA only initially is fine, but we shouldn't plan for > breaking compatibility with an established binding just a short time > later. > [Loc Ho] I will document them as XXGbps and drop the term GenX. As of right now, we only have SATA and I will document on 1.5Gbps, 3.0Gbps, and 6Gbps. Also, keep in mind that these override are used for SATA. PCIe doesn't need these custom override setting per port at this time. A single value so far work just fine for PCIe, SGMII, and XFI. Any other comments... -Loc -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
