From: "Philippe Mathieu-Daudé" <f4bug@amsat.org>
To: Huacai Chen <chenhuacai@kernel.org>
Cc: Peter Maydell <peter.maydell@linaro.org>,
Aleksandar Rikalo <aleksandar.rikalo@syrmia.com>,
Luc Michel <luc@lmichel.fr>,
QEMU Developers <qemu-devel@nongnu.org>,
Hao Wu <wuhaotsh@google.com>,
Aurelien Jarno <aurelien@aurel32.net>
Subject: Re: [RFC PATCH-for-6.1 v2 6/6] hw/mips/loongson3_virt: Raise CPU clock to 2 GHz
Date: Sat, 10 Apr 2021 16:05:51 +0200 [thread overview]
Message-ID: <9f07acda-8949-de4e-a00a-192a4b3c6179@amsat.org> (raw)
In-Reply-To: <CAAhV-H76XQZxvp9b2fE-R-Eq26GViaPR-iC2tG6PYhWtxNasxA@mail.gmail.com>
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 <f4bug@amsat.org> 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.
prev parent reply other threads:[~2021-04-10 14:07 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-09 9:36 [RFC PATCH-for-6.1 v2 0/6] target/mips/cp0_timer: Use new clock_ns_to_ticks() Philippe Mathieu-Daudé
2021-04-09 9:36 ` [RFC PATCH-for-6.1 v2 1/6] target/mips/cpu: Use clock_has_source() instead of clock_get() Philippe Mathieu-Daudé
2021-04-09 16:13 ` Richard Henderson
2021-04-09 9:36 ` [RFC PATCH-for-6.1 v2 2/6] target/mips/cpu: Update CP0 clock when CPU clock is propagated Philippe Mathieu-Daudé
2021-04-09 16:13 ` Richard Henderson
2021-04-09 9:36 ` [RFC PATCH-for-6.1 v2 3/6] target/mips/cp0_timer: Add ns_to_count() helper Philippe Mathieu-Daudé
2021-04-09 16:15 ` Richard Henderson
2021-04-09 9:36 ` [RFC PATCH-for-6.1 v2 4/6] target/mips/cp0_timer: Add ns_substract_to_count() helper Philippe Mathieu-Daudé
2021-04-09 16:27 ` Richard Henderson
2021-04-09 9:36 ` [RFC PATCH-for-6.1 v2 5/6] target/mips/cp0_timer: Use new clock_ns_to_ticks() Philippe Mathieu-Daudé
2021-04-09 16:42 ` Richard Henderson
2021-04-09 9:36 ` [RFC PATCH-for-6.1 v2 6/6] hw/mips/loongson3_virt: Raise CPU clock to 2 GHz Philippe Mathieu-Daudé
2021-04-10 2:43 ` Huacai Chen
2021-04-10 14:05 ` Philippe Mathieu-Daudé [this message]
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