Re: [PATCH for-5.1] hw/arm/netduino2, netduinoplus2: Set system_clock_scale

[Philippe Mathieu-Daudé]

On 7/27/20 8:05 PM, Philippe Mathieu-Daudé wrote:
> On 7/27/20 6:26 PM, Peter Maydell wrote:
>> The netduino2 and netduinoplus2 boards forgot to set the system_clock_scale
>> global, which meant that if guest code used the systick timer in "use
>> the processor clock" mode it would hang because time never advances.
>>
>> Set the global to match the documented CPU clock speed of these boards.
>> Judging by the data sheet this is slightly simplistic because the
>> SoC allows configuration of the SYSCLK source and frequency via the
>> RCC (reset and clock control) module, but we don't model that.
>>
>> Fixes: https://bugs.launchpad.net/qemu/+bug/1876187
>> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
>> ---
>> NB: tested with "make check" only...
> 
> What about adding another patch with:
> 
> -- >8 --
> --- a/hw/timer/armv7m_systick.c
> +++ b/hw/timer/armv7m_systick.c
> @@ -17,6 +17,7 @@
>  #include "qemu/timer.h"
>  #include "qemu/log.h"
>  #include "qemu/module.h"
> +#include "qapi/error.h"
>  #include "trace.h"
> 
>  /* qemu timers run at 1GHz.   We want something closer to 1MHz.  */
> @@ -221,6 +222,11 @@ static void systick_instance_init(Object *obj)
>  static void systick_realize(DeviceState *dev, Error **errp)
>  {
>      SysTickState *s = SYSTICK(dev);
> +
> +    if (!system_clock_scale) {
> +        error_setg(errp, "can not use systick with 'system_clock_scale
> = 0'");
> +        return;
> +    }
>      s->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, systick_timer_tick, s);
>  }

Hmm testing the microbit:

$ qemu-system-arm -M microbit
qemu-system-arm: can not use systick with 'system_clock_scale = 0'

> 
> ---
> 
> I'll try to review with the datasheets tomorrow morning in case you want
> to get it merged during the day.
> 
>>
>>  hw/arm/netduino2.c     | 10 ++++++++++
>>  hw/arm/netduinoplus2.c | 10 ++++++++++
>>  2 files changed, 20 insertions(+)
>>
>> diff --git a/hw/arm/netduino2.c b/hw/arm/netduino2.c
>> index 79e19392b56..8f103341443 100644
>> --- a/hw/arm/netduino2.c
>> +++ b/hw/arm/netduino2.c
>> @@ -30,10 +30,20 @@
>>  #include "hw/arm/stm32f205_soc.h"
>>  #include "hw/arm/boot.h"
>>  
>> +/* Main SYSCLK frequency in Hz (120MHz) */
>> +#define SYSCLK_FRQ 120000000ULL
>> +
>>  static void netduino2_init(MachineState *machine)
>>  {
>>      DeviceState *dev;
>>  
>> +    /*
>> +     * TODO: ideally we would model the SoC RCC and let it handle
>> +     * system_clock_scale, including its ability to define different
>> +     * possible SYSCLK sources.
>> +     */
>> +    system_clock_scale = NANOSECONDS_PER_SECOND / SYSCLK_FRQ;
>> +
>>      dev = qdev_new(TYPE_STM32F205_SOC);
>>      qdev_prop_set_string(dev, "cpu-type", ARM_CPU_TYPE_NAME("cortex-m3"));
>>      sysbus_realize_and_unref(SYS_BUS_DEVICE(dev), &error_fatal);
>> diff --git a/hw/arm/netduinoplus2.c b/hw/arm/netduinoplus2.c
>> index 958d21dd9f9..68abd3ec69d 100644
>> --- a/hw/arm/netduinoplus2.c
>> +++ b/hw/arm/netduinoplus2.c
>> @@ -30,10 +30,20 @@
>>  #include "hw/arm/stm32f405_soc.h"
>>  #include "hw/arm/boot.h"
>>  
>> +/* Main SYSCLK frequency in Hz (168MHz) */
>> +#define SYSCLK_FRQ 168000000ULL
>> +
>>  static void netduinoplus2_init(MachineState *machine)
>>  {
>>      DeviceState *dev;
>>  
>> +    /*
>> +     * TODO: ideally we would model the SoC RCC and let it handle
>> +     * system_clock_scale, including its ability to define different
>> +     * possible SYSCLK sources.
>> +     */
>> +    system_clock_scale = NANOSECONDS_PER_SECOND / SYSCLK_FRQ;
>> +
>>      dev = qdev_new(TYPE_STM32F405_SOC);
>>      qdev_prop_set_string(dev, "cpu-type", ARM_CPU_TYPE_NAME("cortex-m4"));
>>      sysbus_realize_and_unref(SYS_BUS_DEVICE(dev), &error_fatal);
>>
> 
>