[qemu-xen staging] hw/arm/nrf51_soc: Set system_clock_scale

[patchbot@xxxxxxx]

commit ce4f70e81ed23c93ff39234672aff33114532640
Author:     Peter Maydell <peter.maydell@xxxxxxxxxx>
AuthorDate: Mon Jul 27 20:34:58 2020 +0100
Commit:     Peter Maydell <peter.maydell@xxxxxxxxxx>
CommitDate: Mon Aug 3 17:55:31 2020 +0100

    hw/arm/nrf51_soc: Set system_clock_scale
    
    The nrf51 SoC model wasn't setting 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 for this SoC.
    
    This SoC in fact doesn't have a SysTick timer (which is the only thing
    currently that cares about the system_clock_scale), because it's
    a configurable option in the Cortex-M0. However our Cortex-M0 and
    thus our nrf51 and our micro:bit board do provide a SysTick, so
    we ought to provide a functional one rather than a broken one.
    
    Signed-off-by: Peter Maydell <peter.maydell@xxxxxxxxxx>
    Reviewed-by: Philippe Mathieu-Daudé <f4bug@xxxxxxxxx>
    Message-id: 20200727193458.31250-1-peter.maydell@xxxxxxxxxx
---
 hw/arm/nrf51_soc.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/arm/nrf51_soc.c b/hw/arm/nrf51_soc.c
index 45e6cc97d7..e15981e019 100644
--- a/hw/arm/nrf51_soc.c
+++ b/hw/arm/nrf51_soc.c
@@ -32,6 +32,9 @@
 
 #define BASE_TO_IRQ(base) ((base >> 12) & 0x1F)
 
+/* HCLK (the main CPU clock) on this SoC is always 16MHz */
+#define HCLK_FRQ 16000000
+
 static uint64_t clock_read(void *opaque, hwaddr addr, unsigned int size)
 {
     qemu_log_mask(LOG_UNIMP, "%s: 0x%" HWADDR_PRIx " [%u]\n",
@@ -65,6 +68,8 @@ static void nrf51_soc_realize(DeviceState *dev_soc, Error 
**errp)
         return;
     }
 
+    system_clock_scale = NANOSECONDS_PER_SECOND / HCLK_FRQ;
+
     object_property_set_link(OBJECT(&s->cpu), "memory", OBJECT(&s->container),
                              &error_abort);
     if (!sysbus_realize(SYS_BUS_DEVICE(&s->cpu), errp)) {
--
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