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

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

Hi Chen-Yu and Sebastian,

Thanks for looking at this.

On 9/30/26 3:17 AM, Chen-Yu Tsai wrote:
> The syscon node is the provider of the regmap. You need to fix it there,
> not duplicate it in the consumer.

Unless I'm misunderstanding, no driver binds to that node, so its regmap 
comes from the generic syscon code, and changing it there would affect 
every syscon. Lee, Arnd, Mark, would that be acceptable?

These are the options I see. Please let me know if there's a better one:

- Do what Sebastian suggested and make syscon use a raw spinlock, except 
when the node has a clock, since regmap-mmio calls clk_enable() under 
the lock. Off PREEMPT_RT, nothing changes. On RT the lock would no 
longer be preemptible for most syscons, including across bulk writes. 
Most syscon users that do bulk writes only write a few registers, but 
enabling the Amlogic G12A PCIe PLL writes a sequence with 40 us of 
udelay() under the lock.
- Have the pinctrl ioremap() the node a second time alongside syscon's 
mapping and read the input register (DIN) with readl(). That read is the 
only access the EINT code makes in raw context. This would go around the 
syscon, and it requires that DIN never be written in a multi-step 
sequence, which is currently the case.

I'd like to know the best approach before sending out a v2.

Best regards,
Ryan Brue