Beaglebone Serial Ports Progress

[Damjan Marion]

On Feb 15, 2013, at 12:20 PM, Iain Young <iain at g7iii.net> wrote:

> Hi Folks,
> 
> After waiting for deliveries, and a few false starts, I have made
> -some- progress on adding support for the Beaglebone's serial ports
> (UARTS1-5) to FreeBSD
> 
> First thing I did was add the pinmux stuff, having worked out exactly
> what I needed to add to the DTS, and recompile. This seems to have
> worked out well, and on a reboot I see:
> 
> setting internal 28 for uart1_rxd
> setting internal 0 for uart1_txd
> 
> 
> This is good. kernel comes up,curiously though, I don't see lines
> output for the RTS and CTS lines (which I do set to the correct mode,
> yet I do for UART3 CTS and UART4 CTS, which I added as a test.
> 
> I then proceeded to add  the uart1 device itself to the DTS, and
> added the following:
> 
> 	uart1: serial at 48022000 {
>                        compatible = "ns16550";
>                        reg = <0x48022000 0x1000>;
>                        reg-shift = <2>;
>                        interrupts = < 73 >;
>                        interrupt-parent = <&AINTC>;
>                        clock-frequency = < 48000000 >;
>                };
> 
> This caused the kernel to dump me in db (debugger I guess). I figured
> out that 't' gave me a trace, and it looked like it was in the middle
> of probing for UARTS. (This is about as much knowledge I have about the
> kernel debugger)
> 
> I tried changing 0x1000 for 0x2000, as it seems the next reg is also
> reserved for UART1. No more luck. So, thinking I needed to add it as an
> alias (as UART0 is), I added that, but it still dumped me at the
> debugger on boot.
> 
> The only other thing is reg-shift. I must confess, I am a bit blind
> here. Not knowing what it actually did I left it as with UART0. I'm
> hoping it essentially includes the next register up for UART1, as
> while that's listed as "Reserved" in the memory map [Yes, I consulted
> SPRUH73G :)] , it seems to be reserved for UART1, but I am just
> guessing (Yes, I know, not good practice when kernel hacking...)
> 
> I've attached the latest version of my patch, the output from the
> kernel until it blows up, as well as the trace. Patch is based on
> r246610
> 
> Anyone able to point me in the right direction ? I can't be too far
> away, and I can then add UART2-5, and submit an actual working patch!
> 

It is very likely that clock is disabled for USART1. Problem is that usart uses
standard serial driver which is not requesting clock to be enabled during the attach
by invoking ti_prcm_clk_enable().

Can you try to put following at the end of am335x_prcm_attach()?

	prcm_write_4(6c, 2);


This should be register CM_PER_UART1_CLKCTRL.

Damjan