Re: [PATCH v6 08/12] arm64: dts: nuvoton: Add initial ma35d1 device tree

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Dear Stephen,

On 2023/3/29 上午 10:46, Stephen Boyd wrote:
Quoting Jacky Huang (2023-03-28 19:39:36)
On 2023/3/29 上午 10:19, Stephen Boyd wrote:
What do you use the syscon for then? The clock driver must want to use
the syscon for something, implying that they are the same device.
The register lock mechanism is applied to protect many critical
registers from false written.
The register lock control register is one register in system controller.
Some registers of the clock controller are lock protected. Not only
clock controller, but other
IP such as RTC, PWM, ADC, etc, also have lock protected registers. All
these IP requires
syscon to access the lock/unlock control register in the system controller.
That's why we add a <&sys> to the clock controller.

Should we implement a ma35d1-sysctl driver to protect register_lock()
and register_unlock()
and export to those drivers?  If yes, we can remove the <&sys> from
clock controller.

You can implement the lock and unlock in the hwspinlock framework. See

I may not explain clearly enough. The lock/unlock register of system controller is more like a kind of write protection for specific registers, rather than preventing hetero-core CPU access.
In many different IP of ma35d1 contain write protected registers.
In fact, ma35d1 has a "hardware semaphore" IP, and we have implemented the driver in drivers/hwspinlock.
Even the control register of "hardware semaphore" is also write protected.

So, should we implement a system controller driver to provide register_unlock() function?
Is it OK to have such a driver in drivers/mfd?
Or, just use syscon in device tree for those devices that have write protect registers.

Best regards,
Jacky Huang

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