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Re: [PATCH 00/16] hw/mips: Set CPU frequency
From: |
Philippe Mathieu-Daudé |
Subject: |
Re: [PATCH 00/16] hw/mips: Set CPU frequency |
Date: |
Wed, 30 Sep 2020 12:13:20 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 |
On 9/30/20 9:40 AM, Igor Mammedov wrote:
> On Mon, 28 Sep 2020 19:15:23 +0200
> Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>
>> All the MIPS cores emulated by QEMU provides the Coproc#0
>> 'Count' register which can be used as a free running timer.
>>
>> Since it's introduction in 2005 this timer uses a fixed
>> frequency of 100 MHz (for a CPU freq of 200 MHz).
>> While this is not an issue with Linux guests, it makes
>> some firmwares behave incorrectly.
>>
>> The Clock API allow propagating clocks. It is particularly
>> useful when hardware dynamicly changes clock frequencies.
>>
>> To be able to model such MIPS hardware, we need to refactor
>> the MIPS hardware code to handle clocks.
>>
>> This series is organized as follow:
>>
>> - let all CPU have an input clock,
>> - MIPS CPU get an input clock
>> - when the clock is changed, CP0 timer is updated
>> - set correct CPU frequencies to all boards
>> - do not allow MIPS CPU without input clock
>
> is this clock an integral part of MIPS cpus or it's an external device?
CPU cores are clocked via an external clock.
This clock can be on the board (from a crystal oscillator to
complex PLL) or on-chip for some system-on-chip.
In all the (current) QEMU MIPS machines it is external although.
Regards,
Phil.
- Re: [PATCH 16/16] tests/acceptance: Test the MIPSsim machine, (continued)
- Re: [PATCH 16/16] tests/acceptance: Test the MIPSsim machine, Willian Rampazzo, 2020/09/28
- Re: [PATCH 16/16] tests/acceptance: Test the MIPSsim machine, Philippe Mathieu-Daudé, 2020/09/29
- Re: [PATCH 16/16] tests/acceptance: Test the MIPSsim machine, Alex Bennée, 2020/09/29
- Re: [PATCH 16/16] tests/acceptance: Test the MIPSsim machine, Philippe Mathieu-Daudé, 2020/09/29
- Re: [PATCH 16/16] tests/acceptance: Test the MIPSsim machine, Daniel P . Berrangé, 2020/09/30
- Re: [PATCH 16/16] tests/acceptance: Test the MIPSsim machine, Alex Bennée, 2020/09/30
- Re: [PATCH 16/16] tests/acceptance: Test the MIPSsim machine, Philippe Mathieu-Daudé, 2020/09/30
Re: [PATCH 00/16] hw/mips: Set CPU frequency, no-reply, 2020/09/28
Re: [PATCH 00/16] hw/mips: Set CPU frequency, Igor Mammedov, 2020/09/30
- Re: [PATCH 00/16] hw/mips: Set CPU frequency,
Philippe Mathieu-Daudé <=