Re: [PATCH] mfd/rk8xx: fix sleep during RCU read side critical section

[Pavel Skripkin <paskripkin@gmail.com>]

Hi Eric,

Eric Anderson <ejona86@gmail.com> says:
> On Thu, Oct 29, 2026 at 12:22 PM Pavel Skripkin <paskripkin@gmail.com> wrote:
>> SPI does not support atomic transfers, so it's dangerous to call from
>> atomic notif chains, since it can cause stall during reboot on
>> orangepi5 (see trace below).
> 
> For my curiosity, is the hang during reboot/shutdown random or consistent?
> 

They are basically the same, since they both trigger sleeping SPI I/O. I 
agree, I should have used studown/reboot more consistently in commit 
message...

> You are explicitly mentioning reboot, although the stack trace is for
> shutdown. I'd have expected reboot to have always been broken for you.

Likely. I've just bought it, so cannot say if it was always broken. 
Based on code I believe that it was indeed broken from the beginning. 
Also I've found previous attempt to fix it [1], so looks like problem is 
known for quite a long time

> In my change I noticed that reboot and shutdown didn't agree on
> whether to use _PREPARE, and my change adjusted shutdown to agree with
> reboot. Since you apparently need the opposite, prior to my change I'd
> assume shutdown was working but reboot broken.
> 
 >> I don't have rk3288 board to test. However, I strongly suspect 
that>> patch does not affect your case.
> 
> I'll test it this weekend. I suspect it would work fine on Veyron/rk3288.


[1] 
https://lists.infradead.org/pipermail/linux-rockchip/2024-July/049312.html


With regards,
Pavel Skripkin