On Tue, 2016-12-06 at 01:34 -0500, Jon Masters wrote: > On 12/05/2016 10:55 PM, Duc Dang wrote: > > > > On Mon, Dec 5, 2016 at 6:27 PM, Jon Masters <jcm@xxxxxxxxxx> wrote: > > > > > > Hi Duc, all, > > > > > > So after regenerating the initrd override (I must have fat fingered) > > > it is now detecting the correct bit width on boot (attached dmesg log). > > > > > > HOWEVER while the console does come up, the use of "earlycon" on the > > > command line (with no parameters) doesn't result in the early SPCR > > > console coming up correctly. I see some garbled characters that > > > suggest the baud (or register access width) is off somewhere. > > My bad that I did not catch this in the morning. Yes, earlycon does > > not seems to work as expected. I can see that earlycon parameters > > seems to be correct, but the bootconsole message does not come out > > (the following is from 'dmesg') > > > > [ 0.000000] ACPI: SPCR: console: uart,mmio32,0x1c020000,115200 > > [ 0.000000] earlycon: uart0 at MMIO32 0x000000001c020000 (options '115200') > > [ 0.000000] bootconsole [uart0] enabled > The difference appears to be in the baud rate. When I explicitly specify > "earlycon=uart8250,mmio32,0x1c021000" no baud is set. When booting with > the SPCR, the baud is set to 9600 in my case or 115200 in yours. But we > both know that the base clock on the X-Gene UART is weird. Maybe > somehow we can explain this through the lack of setting a baud. BTW, this behavior is same with devicetree. If you specify a baudrate with earlycon=, the driver tries to set that baudrate and if you have an 8250 with some non-standard baud clock, then it will fail. Perhaps SPCR shouldn't pass baud option to setup_earlycon(). Then again, setup_earlycon() has this comment: * setup_earlycon - match and register earlycon console * @buf: earlycon param string * * Registers the earlycon console matching the earlycon specified * in the param string @buf. Acceptable param strings are of the form * <name>,io|mmio|mmio32|mmio32be,<addr>,<options> * <name>,0x<addr>,<options> * <name>,<options> * <name> * * Only for the third form does the earlycon setup() method receive the * <options> string in the 'options' parameter; all other forms set * the parameter to NULL. That part about the 3rd form doesn't seem to be true. I don't see where options gets set to NULL for forms other than the third. > > I am pondering some more currently. If it's X-Gene specific, let's add > that to the quirk (and to perhaps a more APM specific SPCR subtype). > > Jon. > -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
