linux-kernel - Re: [BUG] Rockchip SPI: Runtime PM usage count underflow!

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Message-ID: <CAAMcf8DZu4B2AN+=8xP3wuknqUtD-e-v+Ej31=08ibPfyL+dGw@mail.gmail.com>
Date: Mon, 19 Aug 2024 04:12:58 +0200
From: Vicente Bergas <vicencb@...il.com>
To: "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>, linux-spi@...r.kernel.org, 
	Mark Brown <broonie@...nel.org>, Heiko Stuebner <heiko@...ech.de>
Cc: linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>, 
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] Rockchip SPI: Runtime PM usage count underflow!

On Sun, Aug 18, 2024 at 8:13 PM Vicente Bergas <vicencb@...il.com> wrote:
>
> Hi,
> i am a user of the CONFIG_SPI_SPIDEV device.
> It stopped working between 6.8 and 6.10.5.
> The SPI bus itself reports no errors to userspace, but no devices
> appear connected to the bus.
> The platform used is RK3328.
> The only spi-related message in dmesg is:
> rockchip-spi ff190000.spi: Runtime PM usage count underflow!
>
> Please, can somebody review this issue?
>
> Regards,
>   Vicente.

I've tried to bisect, but there is some strange behaviour:
The message "Runtime PM usage count underflow!" can also appear on a
good kernel.
In order to have a reasoble iteration speed, i am updating the kernel via kexec.
If a good kernel (6.6.30) is cold-booted, then, all the kernels
kexec'd from it work too.
If a bad kernel (6.10.5) is cold-booted, then a 6.6.30 is kexec'd and
then the same 6.10.5 is kexec'd it becomes a good one.