linux-kernel - Re: [PATCH v12 1/1] serial: core: Start managing serial controllers to enable runtime PM

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20230603054139.GR14287@atomide.com>
Date:   Sat, 3 Jun 2023 08:41:39 +0300
From:   Tony Lindgren <tony@...mide.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Chen-Yu Tsai <wenst@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...el.com>,
        Dhruva Gole <d-gole@...com>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        Johan Hovold <johan@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-omap@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v12 1/1] serial: core: Start managing serial controllers
 to enable runtime PM

Hi,

* John Ogness <john.ogness@...utronix.de> [230602 10:13]:
> Unfortunately next-20230601 also brought in a series that added
> spinlocking to the 8250 driver. That may be the issue here instead.

I think you're off the hook here with the spinlocking changes :)

My guess right now is that 8250_mtk does not want runtime PM resume called
on probe for some reason, and assumes it won't happen until until in
mtk8250_do_pm()?

Looking at the probe, the driver does pm_runtime_enable(), but then calls
mtk8250_runtime_resume() directly. Not sure what the intention here is.
Maybe adding pm_runtime_set_active() in probe might provide more clues.

When we add the new serial_ctrl and serial_port devices, their runtime PM
functions propagate to the parent 8250_mtk device. And then something goes
wrong, well this is my guess on what's going on..

To me it seems the 8250_mtk should just do pm_runtime_resume_and_get()
instead of mtk8250_runtime_resume(), then do pm_runtime_put() at the end
of the probe?

I don't think 8250_mtk needs to do register access before and after the
serial port registration, but if it does, then adding custom read/write
functions can be done that do not rely on initialized port like
serial_out().

Looking at the kernelci.org test boot results for Linux next [0], seems
this issue is somehow 8250_mtk specific. I don't think the rk3399 boot
issue is serial port related.

Regards,

Tony

[0] https://linux.kernelci.org/test/job/next/branch/master/kernel/next-20230602/plan/baseline/