On Wed, Sep 16, 2009 at 07:44:07AM +1000, Benjamin Herrenschmidt wrote: >On Tue, 2009-09-15 at 11:32 -0400, Josh Boyer wrote: >> On Tue, Sep 15, 2009 at 10:31:36AM -0400, Paul Gortmaker wrote: >> >One of the guys here was getting a messed up console on a bamboo board >> >(on linux boot), which he traced to the fact that the default dts has a >> >9600 baudrate coded into it (board was running 115k2, not 9600). Either >> >deleting the line, or replacing the 9600 with zero fixed the problem. >> >> Once booted, was there a valid current-speed property in /proc/device-tree >> for the serial node? I'm curious if U-Boot created it, or if the kernel >> just used whatever baud was present already. >> >> When I did the bamboo port a while ago, I recall having issues with either >> a missing clock-frequency or current-speed (or both perhaps) and the >> bootloader >> on the board was the original PIBS. It might have been an issue with PIBS >> but I'm guessing the rest of the 4xx boards copied from either Ebony or >> Bamboo in their ports and hence contain that property. > >I think I recently added code to legacy_serial probe the speed from the >HW if the property is absent, which should help.
Ok, so I think that is related to what I originally hit. I played around with removing the current-speed property on canyonlands today, and noticed that I would get no console output at all unless I specified a baudrate with console=ttyS0,115200. That was sort of contrary to what I found with bamboo, so I diffed the configs to see why. Bamboo has udbg enabled and hence has legacy_serial builtin, whereas canyonlands just has of_serial. So on boards where of_serial is the only serial driver, we need either an accurate current-speed property, or a specific baudrate on the command line. That makes a bit more tenuous to remove the properties entirely, because if people disable udbg and are relying on that behavior they get no more console output. Need to think on that a bit I guess. Alternatively, we could try patching of_serial.c to do the baudrate probe as well. josh _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev