linux-kernel - Re: [PATCH] serial: 8250_dw: Handle no_console

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Message-ID: <20141128120929.GC28114@kuha.fi.intel.com>
Date:	Fri, 28 Nov 2014 14:09:29 +0200
From:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:	Loic Poulain <loic.poulain@...el.com>
Cc:	Doug Anderson <dianders@...omium.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Heiko Stuebner <heiko@...ech.de>, Jiri Slaby <jslaby@...e.cz>,
	Chris Zhong <zyw@...k-chips.com>,
	linux-rockchip@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org,
	Andrew Bresticker <abrestic@...omium.org>,
	mika.westerberg@...ux.intel.com, andriy.shevchenko@...ux.intel.com,
	wens@...e.org, alan@...ux.intel.com, linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] serial: 8250_dw: Handle no_console_suspend when uart
 loses state

On Mon, Nov 17, 2014 at 09:56:08AM +0100, Loic Poulain wrote:
> >In certain suspend modes on certain boards the 8250 UART may lose
> >state when the device goes to suspend.  If we're using
> >no_console_suspend this can cause lots of problems during resume.
> >
> >Let's cache the basic UART config registers at suspend time and if we
> >notice that the UART loses state (by looking at a canary stored in the
> >scratch register) we'll restore it.
> 
> If I'm not wrong, it's already done in acpi_lpss suspend/resume (for
> 8250_dw).
> Commit c78b0830667a7e7c1f0ca65b76b33166a84806b3.

FYI, we are not saving any UART specific registers in acpi_lpss.c nor
any other bus controller's registers that are part of the LPSS block.
We are saving/restoring only the context of lpss specific register
there.

Cheers,

-- 
heikki
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