linux-kernel - Re: [PATCH 0/2] Reset realtek bluetooth devices during user suspend

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Date:   Wed, 18 Sep 2019 16:41:24 +0200
From:   Oliver Neukum <oneukum@...e.com>
To:     Abhishek Pandit-Subedi <abhishekpandit@...omium.org>,
        linux-bluetooth@...r.kernel.org, linux-usb@...r.kernel.org
Cc:     dianders@...omium.org, Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Hui Peng <benquike@...il.com>, linux-pm@...r.kernel.org,
        Johan Hedberg <johan.hedberg@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mark Brown <broonie@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Wolfram Sang <wsa@...-dreams.de>, linux-kernel@...r.kernel.org,
        Marcel Holtmann <marcel@...tmann.org>,
        Len Brown <len.brown@...el.com>,
        Mathias Payer <mathias.payer@...elwelt.net>,
        Dmitry Torokhov <dtor@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mans Rullgard <mans@...sr.com>, Pavel Machek <pavel@....cz>,
        YueHaibing <yuehaibing@...wei.com>
Subject: Re: [PATCH 0/2] Reset realtek bluetooth devices during user suspend

Am Dienstag, den 17.09.2019, 14:27 -0700 schrieb Abhishek Pandit-
Subedi:
> On a Realtek USB bluetooth device, I wanted a simple and consistent way
> to put the device in reset during suspend (2 reasons: to save power and

The device really uses less power if you reset it before suspendening
it?

> disable BT as a wakeup source). Resetting it in the suspend callback

Then do not enable it. Something is strange.

> causes a detach and the resume callback is not called. Hence the changes
> in this series to do the reset in suspend_noirq.
> 
> I looked into using PERSIST and reset on resume but those seem mainly
> for misbehaving devices that reset themselves.

No, not really. It is also for device that need to be reset if you use
the RESET_RESUME quirk. But that is on resume().
You could introduce a new flag. But the _noirq method is kind of
a hack, as USB really cannot operate without interrupts.

	Regards
		Oliver