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

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Message-ID: <20100113134445.010d4f1c@lxorguk.ukuu.org.uk>
Date:	Wed, 13 Jan 2010 13:44:45 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Chaithrika U S <chaithrika@...com>
Cc:	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	davinci-linux-open-source@...ux.davincidsp.com,
	khilman@...prootsystems.com, akpm@...ux-foundation.org,
	Chaithrika U S <chaithrika@...com>
Subject: Re: [PATCH] serial: 8250: Add cpufreq support

> +static int serial8250_cpufreq_transition(struct notifier_block *nb,
> +					     unsigned long val, void *data)
> +{
> +	struct uart_8250_port *p;
> +	struct uart_port *uport;
> +
> +	p = container_of(nb, struct uart_8250_port, freq_transition);
> +	uport = &p->port;
> +
> +	if (IS_ERR(p->clk))
> +		goto cpu_freq_exit;
> +
> +	if (p->port.uartclk == clk_get_rate(p->clk))
> +		goto cpu_freq_exit;
> +
> +	p->port.uartclk = clk_get_rate(p->clk);
> +	if (val == CPUFREQ_POSTCHANGE) {
> +		struct ktermios *termios;
> +		struct tty_struct *tty;
> +		if (uport->state == NULL)
> +			goto cpu_freq_exit;
> +
> +		tty = uport->state->port.tty;

Need locking on port->tty.

> +		if (tty == NULL)
> +			goto cpu_freq_exit;
> +

Need locking on tty->termios

I'd say this is also probably at the wrong level - why not do it at the
uart_port level instead (ie move the code you have into serial_core using
uart_port) - you've made it all nicely generic already.

Alan
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