Hi Aleksey, On 12/06/2016 12:58 PM, Aleksey Makarov wrote: > It turns out that this approach does not work for all the existing hardware. > There are two problems with AppliedMicro X-Gene based boards > ([discussion], [v1]): > > 1. Their console is a 16550 port that requires 32-bit access. Now SPCR does not > have any method to specify this. > > 2. Some of the boards don't use the "standard" 16550 clock rate so supplying > a baud rate makes it change to a random baud rate. > > Patch 1/4 uses 'Register Bit Width' field of the ACPI Generic Address > Structure that specifies the address of the UART registers to > decide if the driver should use "mmio32" access instead of "mmio". > This fixes problem 1 for existing hardware/firmware. > > To fix problem 2, I suggest to introduce a new value '0' for the "Baud Rate" > field of SPCR (now this value is reserved). I would like to discuss if this > could be added to SPCR spec and will fix the problem. Part 1 could well be solved in this way, provided it can be made part of the mainstream specification. It seems fairly reasonable, however. I'm not sure I subscribe to part 2 because there could be all manner of havoc changing the interpretation of existing zero values. That is why I personally favor an AppliedMicro SPCR subtype specific to them. That all said, I did discuss exactly part 2 with the folks responsible for the SPCR specification and they are thinking about their preferred solution, which will likely either be a new subtype for Applied, or perhaps allow for what you describe. I will followup when I know. Jon. -- Computer Architect | Sent from my Fedora powered laptop -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
