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

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Message-ID: <6138a97f-1b8b-f33f-8be5-e2141314dbd7@collabora.com>
Date:   Wed, 7 Jun 2023 09:17:17 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Chen-Yu Tsai <wenst@...omium.org>, Tony Lindgren <tony@...mide.com>
Cc:     John Ogness <john.ogness@...utronix.de>,
        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>, linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v12 1/1] serial: core: Start managing serial controllers
 to enable runtime PM

Il 07/06/23 06:46, Chen-Yu Tsai ha scritto:
> On Tue, Jun 6, 2023 at 8:21 PM Tony Lindgren <tony@...mide.com> wrote:
>>
>> * Chen-Yu Tsai <wenst@...omium.org> [230606 09:17]:
>>> I ended up following 8250_dw's design, which seemed less convoluted.
>>> The original code was waaay too convoluted.
>>
>> OK that looks good to me thanks. Good to hear you got it sorted out.
>>
>> The 8250_dw style runtime PM is a good solution for simple cases. Where
>> it won't work are SoCs where runtime PM calls need to propagate up the
>> bus hierarchy. For example, 8250_omap needs runtime PM calls for the
>> interconnect and power domain to get register access working.
> 
> Good to know. On MediaTek platforms I don't think there are any power
> domains covering the basic peripherals. (Or it's hidden from the kernel.)
> 

On (relatively) new SoCs, basic peripherals are always powered, you're correct.

Cheers,
Angelo

>>> BTW, the Bluetooth breakage seems like a different problem.
>>
>> OK seems like we're good to go then :)
> 
> Yup. After a bit more testing, it seems the Bluetooth problem is more like
> an undervolt issue. If I have WiFi and BT probe at the same time, Bluetooth
> fails. If they probe separately, everything works fine.
> 
> ChenYu