On 03/23/2016 07:09 PM, Matthias Schiffer wrote: >>> autoconfig_16550a() is doing all kinds of weird checks to detect different >>> hardware by writing a lot of register values which are documented as >>> reserved in the AR7242 datasheet (there's a leaked version going around >>> that can be easily googled...), no idea if any of those are problematic. >>> Just setting UPF_FIXED_TYPE as suggested by Peter would avoid that code >>> altogether. >> >> That's just a debugging patch and not appropriate for permanent use, >> the reason being that this uart is _not_ 16550 compatible (or even 16450 >> compatible). >> >> The three options for 8250 driver support for this part are: >> 1. Similar to the debugging patch, set UPF_FIXED_TYPE but set port type >> to PORT_8250 instead. This will lose FIFO support so 115K won't be >> possible and likely neither will 38400. >> >> 2. Set UPF_FIXED_TYPE but define a new PORT_* value and add support for >> this PORT_* value to uart_config array, uapi headers, and anywhere >> the scratch register is used. >> >> 3. As with 2. above but don't set UPF_FIXED_TYPE and add a probe function >> that detects ports of this type to autoconfig(). I don't recommend this >> method. >> >> This requirement is independent of fixing prom_putchar_ar71xx(). >> > > I can send patches for all of this, and I think that 2. would be the nicest > solution. I've noticed though that include/uapi/linux/serial_core.h is > experiencing a little "overflow": PORT_MAX_8250 has grown just below the > first non-8250 entry. Ugh. Thanks for noting this. > Should I just add the new entry at the bottom (and > thus grow the uart_config array by ~85 unused entries)? What about > PORT_MAX_8250 (used at least in drivers/tty/serial/8250/8250_of.c)? None of the above, unfortunately. Ok, plan B. I need to clean off a dusty series that adds probe steering and bugs pass-thru for 8250 sub-drivers and platform data. Then add a UART_BUG_NOSCR to indicate a uart does not have a scratch register (like this one). Then for this uart, set UPF_FIXED_TYPE and type to PORT_16550A, with UART_BUG_NOSCR flag. Couple of days because I'm in the middle of something else, ok? Regards, Peter Hurley
