Re: [Qemu-devel] [Bug 1630723] [NEW] UART writes to netduino2/stm32f205-soc disappear

[Alistair Francis <alistair23@gmail.com>]

On Fri, Oct 7, 2016 at 9:03 AM, Alistair Francis <alistair23@gmail.com> wrote:
> On Fri, Oct 7, 2016 at 8:59 AM, Seth K <skintigh@gmail.com> wrote:
>> The only machine I saw listed in the help output is "netduino2." I pulled
>> QEMU from github, was that the right thing to do?
>>
>> I found the specifications for the stm32f2xx and some similar chips and
>> verified the addresses and interrupts are correct.
>
> Sorry my mistake. It is a the Netduino 2 Plus that we don't support.
>
> I think we should move this conversation to the bug report as well, I
> was hoping that replying to the email would update the bug report but
> it doesn't look like it.
>
>>
>> The stm32f205 should support 6 UARTs, and the 6 addresses and IRQs are coded
>> correctly. However there is a hard-coded value MAX_SERIAL_PORTS limiting
>> serial_hds to 4, and I don't know why. I am considering submitting a patch.
>
> I'm not sure why we have that limit, you can submit a patch and see
> what everyone says.
>
>>
>> If I increase MAX_SERIAL_PORTS I can write to UARTs 1, 4, 5, and 6 and
>> output them to sockets. However writes to UARTs 2 and 3 just disappear. They
>> don't even trigger my printf in stm32f2xx_usart_write. It seems like they
>> are being intercepted somewhere, and unfortunately my knowledge of QEMU is
>> too low to know where to look. Any pointers would be greatly appreciated.
>
> Strange. There could be something else addressed there. If you run
> 'info mtree' at the QEMU prompt (Ctrl-a + c) you should be able to see
> the memory map of the system.

Hey Seth,

What if you try this diff? Does that help?

diff --git a/hw/char/stm32f2xx_usart.c b/hw/char/stm32f2xx_usart.c
index 4c6640d..b07c67b 100644
--- a/hw/char/stm32f2xx_usart.c
+++ b/hw/char/stm32f2xx_usart.c
@@ -204,7 +204,7 @@ static void stm32f2xx_usart_init(Object *obj)
     sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->irq);

     memory_region_init_io(&s->mmio, obj, &stm32f2xx_usart_ops, s,
-                          TYPE_STM32F2XX_USART, 0x2000);
+                          TYPE_STM32F2XX_USART, 0x200);
     sysbus_init_mmio(SYS_BUS_DEVICE(obj), &s->mmio);
 }

Thanks,

Alistair