linux-kernel - Re: [PATCH] serial: 8250: Add cpufreq support

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Message-ID: <20120412104758.3fc8085d@pyramind.ukuu.org.uk>
Date:	Thu, 12 Apr 2012 10:47:58 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	"Shankarmurthy, Akshay" <akshay.s@...com>
Cc:	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	"alan@...ux.intel.com" <alan@...ux.intel.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"paul.gortmaker@...driver.com" <paul.gortmaker@...driver.com>,
	"jamie@...ieiles.com" <jamie@...ieiles.com>,
	"swarren@...dia.com" <swarren@...dia.com>,
	"dianders@...omium.org" <dianders@...omium.org>,
	"davinci-linux-open-source@...ux.davincidsp.com" 
	<davinci-linux-open-source@...ux.davincidsp.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] serial: 8250: Add cpufreq support

> > > I will have a look at this and add the lock if necessary.
> > 
> > At the very least you need reference counts held on the tty struct and to allow for the tty having vanished under you.
> > 
> 
> I am planning to add "tty->termios_mutex" lock. Any comments ?

Explain how this will help. You need a reference count to the tty itself.

> I understand this and planning to avoid unnecessary registration like these. 
> As a solution, UART port's cpu freq status will be sent from the board file.
> Adding a member to the structure "plat_serial8250_port" which says whether
> a port requires cpu freq registration or not. cpu freq register function is
> called in the driver depending upon the status of this structure member.
> I can update the patch accordingly and send out a version 2 to the list.

That sounds sensible.

Alan
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