[PATCH 4/4] cpufreq: add an Amlogic speed-bin driver

[Chuan Liu]

Hi Viresh, Christian,
     Could you please hold off for now on the patches adding cpufreq 
driver support on S4? There are still two issues that need to be 
resolved first:
   - The clock driver currently does not support setting the CPU clock.
   - The CPU regulator needs some time to stabilize after the voltage is 
changed. Without a proper delay, the CPU clock frequency may be raised 
before the regulator voltage has actually reached the target value, 
which can hang the system. The S4 CPU regulator handling currently lacks 
the logic to wait for the regulator voltage to settle, so this part 
needs to be completed first.

We are currently working on submitting our own cpufreq driver. We are 
considering how to address the issues above, taking into account the 
hardware characteristics of previous SoCs and evaluating factors such as 
the transition latency. S4 will be covered by that work (as well as SoCs 
from S4 onward, such as C3, T7, ..., A9). So please give us some time.

On 10/26/2026 4:59 PM, Viresh Kumar wrote:
> On 26-10-26, 09:57, Jerome Brunet wrote:
>> On lun. 26 oct. 2026 at 11:00, Viresh Kumar <viresh.kumar at linaro.org> wrote:
>>
>>> On 25-10-26, 20:22, christian.koever-draxl at student.uibk.ac.at wrote:
>>>> From: Christian Stefan Kövér-Draxl <ckoever at outlook.de>
>>>>
>>>> Every S4 speed bin runs the same CPU frequencies but needs its own
>>>> voltage curve, and the bin can only be read through the secure monitor.
>>>>
>>>> Read the bin from the firmware, select the matching
>>>> "opp-microvolt-speed<bin>" property for all CPUs, then register
>>>> cpufreq-dt. Bins outside the known range fall back to bin 0, which
>>>> has the highest voltages. Like sun50i-cpufreq-nvmem, the driver binds
>>>> on the SoC compatible and needs no node of its own, and S4 is added to
>>>> the cpufreq-dt-platdev blocklist so cpufreq-dt is only created after
>>>> the bin has been applied.
>>>>
>>>> Signed-off-by: Christian Stefan Kövér-Draxl <ckoever at outlook.de>
>>>> ---
>>>>   MAINTAINERS                          |   1 +
>>>>   drivers/cpufreq/Kconfig.arm          |  14 ++
>>>>   drivers/cpufreq/Makefile             |   1 +
>>>>   drivers/cpufreq/amlogic-cpufreq.c    | 184 +++++++++++++++++++++++++++
>>>>   drivers/cpufreq/cpufreq-dt-platdev.c |   2 +
>>>>   5 files changed, 202 insertions(+)
>>>>   create mode 100644 drivers/cpufreq/amlogic-cpufreq.c
>>>
>>> Is it safe to apply just this one ? I can take this via the PM tree then.
>>
>> I would advise to wait a little for Amlogic to chime in.
> 
> Sure, I wasn't going to wait for the maintainers to respond anyway.
> 

-- 
Best regards,
Chuan