CPM UART on MPC8270

[James Black]

I couldn't get the echo > /dev/xxx to work. I had to write a small app
that opened the device and write and read characters for testing.

Start there and you may find it is actually working.

JB

On Wed, Jun 9, 2010 at 8:37 AM, Martyn Welch <martyn.welch at ge.com> wrote:
> Hi All,
>
> I'm attempting to get an SCC port on an MPC8270 working with Linux. I'm
> not overly familiar with the CPM and am having a bit of trouble.
>
> Linux is booting natively on the 8270. I have access to the 8270 via a
> set of PCI windows from a second core (includes one setup over the main
> memory and one over the IMMR) and SMC1 is up and working with a console.
>
> The SCCs seem to be detected correctly at boot:
>
> f011a80.serial: ttyCPM0 at MMIO 0xc3014a80 (irq = 16) is a CPM UART
> f011a00.serial: ttyCPM1 at MMIO 0xc3018a00 (irq = 40) is a CPM UART
> f011a20.serial: ttyCPM2 at MMIO 0xc3020a20 (irq = 41) is a CPM UART
> f011a40.serial: ttyCPM3 at MMIO 0xc3028a40 (irq = 42) is a CPM UART
>
> With the DTS reading:
>
>                        smc1: serial at 11a80 {
>                                device_type = "serial";
>                                compatible = "fsl,mpc8270-smc-uart",
>                                             "fsl,cpm2-smc-uart";
>                                reg = <0x11a80 0x20 0x87fc 2>;
>                                interrupts = <4 8>;
>                                interrupt-parent = <&PIC>;
>                                fsl,cpm-brg = <7>;
>                                fsl,cpm-command = <0x1d000000>;
>                        };
>
>                        scc1: serial at 11a00 {
>                                device_type = "serial";
>                                compatible = "fsl,mpc8270-scc-uart",
>                                             "fsl,cpm2-scc-uart";
>                                reg = <0x11a00 0x20 0x8000 0x100>;
>                                interrupts = <40 8>;
>                                interrupt-parent = <&PIC>;
>                                fsl,cpm-brg = <3>;
>                                fsl,cpm-command = <0x800000>;
>                        };
>
>                        scc2: serial at 11a20 {
>                                device_type = "serial";
>                                compatible = "fsl,mpc8270-scc-uart",
>                                             "fsl,cpm2-scc-uart";
>                                reg = <0x11a20 0x20 0x8100 0x100>;
>                                interrupts = <41 8>;
>                                interrupt-parent = <&PIC>;
>                                fsl,cpm-brg = <6>;
>                                fsl,cpm-command = <0x4a00000>;
>                        };
>
>                        scc3: serial at 11a40 {
>                                device_type = "serial";
>                                compatible = "fsl,mpc8270-scc-uart",
>                                             "fsl,cpm2-scc-uart";
>                                reg = <0x11a40 0x20 0x8200 0x100>;
>                                interrupts = <42 8>;
>                                interrupt-parent = <&PIC>;
>                                fsl,cpm-brg = <1>;
>                                fsl,cpm-command = <0x8c00000>;
>                        };
>
> I believe that I have the pins setup correctly and the BRGs connected
> correctly in the setup_arch function.
>
> At the moment I have SCC3 wired out. If I attempt to echo data out of
> the SCC (echo "Hello" > /dev/ttyCPM3) I get the prompt sits waiting.
> Rebooting and turning on the debug yields the following output on the
> console (but nothing out of the SCC port):
>
> CPM uart[3]:startup
> Interrupt attached
> CPM uart[3]:set_termios
> CPM uart[3]:start tx
> CPM uart[3]:stop tx
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:stop rx
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:shutdown
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> CPM uart[3]:tx_empty: 0
> ...
>
>
> It seemed to be waiting for ready bit of the Transmit Buffer Descriptor
> to be cleared (which it never seems to be), prodding this bit through
> the pci window did cause the process to continue, no data out but I did
> get back to the prompt on the console.
>
> I'm sure I'm just missing something really basic - can anyone enlighten me?
>
> Martyn
>
> --
> Martyn Welch (Principal Software Engineer)   |   Registered in England and
> GE Intelligent Platforms                     |   Wales (3828642) at 100
> T +44(0)127322748                            |   Barbirolli Square, Manchester,
> E martyn.welch at ge.com                        |   M2 3AB  VAT:GB 927559189
>
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev at lists.ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev
>



-- 
Jim Black
Senior Software Engineer
Aztek Networks, Inc.
2477 55th Street, Suite 202
Boulder, CO 80301
www.azteknetworks.com