[LEDE-DEV] MT7620A uart/uartlite no console or shell i/o but dmesg/bootearly0 ok [Edimax BR-6478AC V2]

[John Crispin]

On 18/09/2016 03:33, Rohan Murch wrote:
> Hi all,
> 
> I have been scratching away at an Edimax "BR-6478AC V2" router for a
> few weeks now and have mostly successfully ported OpenWrt DD to this
> model. I am having some major issues with the uart and uartlite serial
> ports on the chip.
> 
> There is most definitely two serial ports, and the factory firmware
> showed "console=ttyS0,57600n8 console=ttyS1". I have found what is
> ttyS1 (uartlite 0xc00) and the front of the board and can get a
> working shell on factory firmware with this port. I can see what looks
> like a 2nd uart port, a row of 4x 2.54mm spaced pins, but they share 4
> pins of the middle ethernet port (LAN3).
> 
> Has anyone heard of a MT7620A uart at 0x500 (ttyS0) sharing 4 pins of
> the ethernet switch?
> 
> Has anyone dealt with the issue of getty/agetty/mingetty quietly doing
> nothing when pointed to an active console, but dying with stderr
> output in boot up when deliberately misconfigured?
> 
> I can get a full complete boot, past preinit, init and procd finished,
> but no shell login. I can successfully configure either just uartlite
> 0xc00 as ttyS0 only, or uartlite 0xc00 as ttyS1 and uart(full) 0xc00
> as ttyS0. They both seem to be working ok according to the kernel boot
> line "console=ttyS0,57600" or "console=ttyS1,57600" (ie: setting 0x500
> as console causes 0xc00 to stop outputting after "disabled bootearly0"
> or "early0". So it appears as though the kernel thinks it has
> correctly grabbed a console to use, but there is nothing outputted,
> and no terminal input is accepted.
> 
> Link to OpenWrt forum thread on this topic:
> https://forum.openwrt.org/viewtopic.php?id=67192
> 
> Any help would be most greatly appreciated!
> 
> Kindest regards, Roh.
> 


Hi Roh,

sorry i am failing to follow the mail ... in short uart full fails and
and uart lite works ?

normally uartlite is used for the console on almost all devices using a
MTK SoC. some very few use uart full. for uart full to also work, the
pinmux must be configured properly.

procd decides which console to use by parsing the kernel commandline,
looking for console=XYZ. this is triggered by the askconsole line inside
/etc/inittab. i am nor sure if it will parse more than 1 console
instance in that line.

	John