Re: [PATCH 00/16] hw/mips: Set CPU frequency

[Igor Mammedov <imammedo@redhat.com>]

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?

> I used a MIPSsim test suggested by Thomas. It is also included
> as bonus at the end.
> 
> Possible follow up:
> - QOM'ify the GIC
> - let the GIC handle dynamic clock changes
> 
> Regards,
> 
> Phil.
> 
> Philippe Mathieu-Daudé (16):
>   hw/core/cpu: Let CPU object have a clock source
>   target/mips: Move cpu_mips_get_random() with CP0 helpers
>   target/mips/cp0_timer: Explicit unit in variable name
>   target/mips/cpu: Introduce mips_cpu_properties[]
>   target/mips/cpu: Set default CPU frequency to 200 MHz
>   target/mips: Keep CP0 counter in sync with the CPU frequency
>   hw/mips/r4k: Explicit CPU frequency is 200 MHz
>   hw/mips/fuloong2e: Set CPU frequency to 533 MHz
>   hw/mips/mipssim: Correct CPU frequency
>   hw/mips/jazz: Correct CPU frequencies
>   hw/mips/cps: Expose input clock and connect it to CPU cores
>   hw/mips/boston: Set CPU frequency to 1 GHz
>   hw/mips/malta: Set CPU frequency to 320 MHz
>   hw/mips/cps: Do not allow use without input clock
>   target/mips/cpu: Do not allow system-mode use without input clock
>   tests/acceptance: Test the MIPSsim machine
> 
>  include/hw/core/cpu.h                    |  5 +++
>  include/hw/mips/cps.h                    |  2 +
>  target/mips/cpu.h                        |  9 ++++
>  target/mips/internal.h                   |  2 +-
>  hw/core/cpu.c                            | 12 +++++
>  hw/mips/boston.c                         | 13 ++++++
>  hw/mips/cps.c                            |  8 ++++
>  hw/mips/fuloong2e.c                      |  8 +++-
>  hw/mips/jazz.c                           | 16 ++++++-
>  hw/mips/malta.c                          | 20 +++++++--
>  hw/mips/mipssim.c                        | 12 ++++-
>  hw/mips/r4k.c                            |  8 +++-
>  target/mips/cp0_helper.c                 | 25 +++++++++++
>  target/mips/cp0_timer.c                  | 51 ++++++---------------
>  target/mips/cpu.c                        | 43 +++++++++++++++++-
>  MAINTAINERS                              |  1 +
>  tests/acceptance/machine_mips_mipssim.py | 56 ++++++++++++++++++++++++
>  17 files changed, 244 insertions(+), 47 deletions(-)
>  create mode 100644 tests/acceptance/machine_mips_mipssim.py
>