Using Mini UART on RPI CM

[Stefan Wahren]

Am 01.10.2015 um 12:12 schrieb Stefan Wahren:
> Am 01.10.2015 um 08:59 schrieb Martin Sperl:
>>> On 30.09.2015, at 22:18, Eric Anholt <eric at anholt.net> wrote:
>>>> Did i miss something in my board dts file to enable the aux uart clock?
>>> That branch looks like it needs the submitted version of "Add a driver
>>> for the auxiliary peripheral clock gates" instead, which I think would
>>> fix this problem.
>>>
>>> https://github.com/anholt/linux/commit/c57cca7e0e96781ba3b9a0d0ab1069c0c20e0677
>> That is my guess as well - and yes, that patch requires the clock-patch
>> of Eric to be installed - I wish it was there already!
>
> Thank you very much, now the driver probing works and the clocks seems
> also okay.
>
> Unfortunately any access to /dev/ttyS0 leads to a system freeze:
>
> NMI watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [bash:2610]
>
> Looks like a irq issue.
>
> Here the relevant dmesg:
>
> [    0.738246] Serial: 8250/16550 driver, 1 ports, IRQ sharing enabled
> [    0.746799] of_serial 20215040.uart: clk or clock-frequency not defined
> ...
> [    2.751262] 20201000.uart: ttyAMA0 at MMIO 0x20201000 (irq = 81,
> base_baud = 0) is a PL011 rev2
> [    3.431447] console [ttyAMA0] enabled
> [    3.449268] 20215040.uart: ttyS0 at MMIO 0x20215040 (irq = 53,
> base_baud = 15612499) is a 16550
>
> Here the relevant config:
>
> CONFIG_GENERIC_IRQ_PROBE=y
> CONFIG_GENERIC_IRQ_SHOW=y
> CONFIG_GENERIC_IRQ_SHOW_LEVEL=y
> CONFIG_HARDIRQS_SW_RESEND=y
> CONFIG_IRQ_DOMAIN=y
> CONFIG_HANDLE_DOMAIN_IRQ=y
> CONFIG_IRQ_FORCED_THREADING=y
> CONFIG_SPARSE_IRQ=y
> CONFIG_GENERIC_CLOCKEVENTS=y
> CONFIG_SERIAL_EARLYCON=y
> CONFIG_SERIAL_8250=y
> CONFIG_SERIAL_8250_CONSOLE=y
> CONFIG_SERIAL_8250_NR_UARTS=1
> CONFIG_SERIAL_8250_RUNTIME_UARTS=1
> CONFIG_SERIAL_8250_EXTENDED=y
> CONFIG_SERIAL_8250_SHARE_IRQ=y
> CONFIG_SERIAL_AMBA_PL011=y
> CONFIG_SERIAL_AMBA_PL011_CONSOLE=y
> CONFIG_SERIAL_CORE=y
> CONFIG_SERIAL_CORE_CONSOLE=y
> CONFIG_CONSOLE_POLL=y
> CONFIG_SERIAL_OF_PLATFORM=y
>
> Here is the pinmuxing for UART1:
>
>      uart1_pins: uart1_pins {
>          brcm,pins = <32 33>;
>          brcm,function = <BCM2835_FSEL_ALT5>;
>          brcm,pull = <0 2>;
>      };
>
> But irq 53 doesn't appear under /proc/interrupts.
>
> Any ideas?
>

I only want to mention that the soft lockup is reproducable with 
Raspberry Pi B and the downstream kernel 3.18 & 4.1.10, too.

Stefan