Re: [RFC PATCH-for-6.1 v2 6/6] hw/mips/loongson3_virt: Raise CPU clock to 2 GHz
Hi Huacai,
On 4/10/21 4:43 AM, Huacai Chen wrote:
> Hi, Philippe,
>
> On Fri, Apr 9, 2021 at 5:36 PM Philippe Mathieu-Daudé wrote:
>>
>> Commit cd3a53b727d ("clock: Add clock_ns_to_ticks() function")
>> removed the limitation of using clock with a frequency of 1 GHz
>> or more.
>>
>> The previous commit converted the MIPS CP0 timer to use this
>> new clock_ns_to_ticks() function. We can now use a clock of
>> 2 GHz with the Loongson3 virt board.
> Yes, we can do this, but why should we do this? I don't think this can
> bring any advantages.
IIRC this was how you sent the earlier series, then we had to reduce
the frequency to <1GHz due to the DIV#0 bug. Now it is fixed I thought
you'd get this back.
I spent time with the R4K timer because it is often used by embedded
firmwares, and a mismatch with the CPU clock makes firmware not work
well. I suppose when using Linux guests it is not a real issue, because
1/ if there is another timer (different peripheral on a system-on-soc)
Linux will use it first, 2/ Linux does some early check to adapt with
the tick rate IIRC (it doesn't assume a precise rate).
I'm fine with the current Loongson3 virt board behavior with TCG,
so let's disregard this patch.
Thanks,
Phil.
Re: [RFC PATCH-for-6.1 v2 6/6] hw/mips/loongson3_virt: Raise CPU clock to 2 GHz
Hi, Philippe,
On Fri, Apr 9, 2021 at 5:36 PM Philippe Mathieu-Daudé wrote:
>
> Commit cd3a53b727d ("clock: Add clock_ns_to_ticks() function")
> removed the limitation of using clock with a frequency of 1 GHz
> or more.
>
> The previous commit converted the MIPS CP0 timer to use this
> new clock_ns_to_ticks() function. We can now use a clock of
> 2 GHz with the Loongson3 virt board.
Yes, we can do this, but why should we do this? I don't think this can
bring any advantages.
Huacai
>
> Signed-off-by: Philippe Mathieu-Daudé
> ---
> hw/mips/loongson3_virt.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/mips/loongson3_virt.c b/hw/mips/loongson3_virt.c
> index b15071defc6..0b72ef8a684 100644
> --- a/hw/mips/loongson3_virt.c
> +++ b/hw/mips/loongson3_virt.c
> @@ -152,7 +152,7 @@ static const MemoryRegionOps loongson3_pm_ops = {
> }
> };
>
> -#define DEF_LOONGSON3_FREQ (800 * 1000 * 1000)
> +#define DEF_LOONGSON3_FREQ (2000 * 1000 * 1000)
>
> static uint64_t get_cpu_freq_hz(void)
> {
> --
> 2.26.3
>
[RFC PATCH-for-6.1 v2 6/6] hw/mips/loongson3_virt: Raise CPU clock to 2 GHz
Commit cd3a53b727d ("clock: Add clock_ns_to_ticks() function")
removed the limitation of using clock with a frequency of 1 GHz
or more.
The previous commit converted the MIPS CP0 timer to use this
new clock_ns_to_ticks() function. We can now use a clock of
2 GHz with the Loongson3 virt board.
Signed-off-by: Philippe Mathieu-Daudé
---
hw/mips/loongson3_virt.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/hw/mips/loongson3_virt.c b/hw/mips/loongson3_virt.c
index b15071defc6..0b72ef8a684 100644
--- a/hw/mips/loongson3_virt.c
+++ b/hw/mips/loongson3_virt.c
@@ -152,7 +152,7 @@ static const MemoryRegionOps loongson3_pm_ops = {
}
};
-#define DEF_LOONGSON3_FREQ (800 * 1000 * 1000)
+#define DEF_LOONGSON3_FREQ (2000 * 1000 * 1000)
static uint64_t get_cpu_freq_hz(void)
{
--
2.26.3
