Re: [PATCH] pinctrl: mediatek: common-v1: Use a raw spinlock for the pinctrl regmap

[Ryan Brue <ryanbrue.dev@gmail.com>]

On 10/20/26 2:32 AM, Sebastian Andrzej Siewior wrote:
> bulk writes could be a concern. The 40us delay is within the lock
> acquired? If so, could this be done without the lock? I assume this is
> part of the init sequence so nothing should use the HW so the writes
> should not be interrupted by other writes to the device.

Yes, it's under the lock. regmap_multi_reg_write() holds the regmap lock 
for the whole sequence, and since an MMIO syscon's regmap can't sleep, 
the delays are udelay()s. The PLL's enable runs that sequence (13 
writes, 40 us of delays) whenever the PLL goes from off to on, retrying 
up to 10 times until it locks.

In practice it's init-time, though. The G12A USB3/PCIe PHY takes the PLL 
with devm_clk_get_enabled() at probe and keeps it on, so it runs only 
once. Nothing else writes the PLL then, but the lock is the HHI 
syscon's, so on RT the other clocks in that block would wait it out. 
Running it without the lock would mean changing how the meson PLL code 
writes its init sequence, which I wouldn't want to take on in a pinctrl 
fix (unless that were preferred).

> So it would be safe for now…
Yes, that's the trade-off with the second option, which relies on the 
DIN never being written in a multi-step sequence. Nothing enforces that 
though.

I'd like to send a v2 after -rc1, but I don't know the best option for 
the fix. Still waiting on Lee, Arnd, and Mark to pitch in if they have a 
preference, or any option I've missed.

Best regards,
Ryan Brue