On Fri, Mar 15, 2013 at 09:15:11PM -0300, Emilio L?pez wrote:

Hello Russell,

El 15/03/13 19:39, Russell King - ARM Linux escribi?:

quoted

On Fri, Mar 15, 2013 at 09:06:23PM +0100, Maxime Ripard wrote:

quoted

+	/* clock got configured through clk api, all done */
+	if (p->uartclk)

	if (IS_ERR(p->uartclk))

Isn't IS_ERR for pointers? p->uartclk is an unsigned int

Right, sorry, ignore that.

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+		return 0;
+
+	/* try to find out clock frequency from DT as fallback */
 	if (of_property_read_u32(np, "clock-frequency", &val)) {
-		dev_err(p->dev, "no clock-frequency property set\n");
+		dev_err(p->dev, "clk or clock-frequency not defined\n");
 		return -EINVAL;
 	}
 	p->uartclk = val;

@@ -294,9 +301,21 @@ static int dw8250_probe(struct platform_device *pdev)
 	if (!uart.port.membase)
 		return -ENOMEM;
 
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(data->clk))
+		data->clk = NULL;
+	else
+		clk_prepare_enable(data->clk);

	if (!IS_ERR(data->clk))
		clk_prepare_enable(data->clk);

See below

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+
 	uart.port.iotype = UPIO_MEM;
 	uart.port.serial_in = dw8250_serial_in;
 	uart.port.serial_out = dw8250_serial_out;
+	uart.port.private_data = data;
+	uart.port.uartclk = clk_get_rate(data->clk);

What if data->clk is invalid?

	if (!IS_ERR(data->clk)
		uart.port.uartclk = clk_get_rate(data->clk);

I'm not sure if it is coincidental or the way it is supposed to be, but
when using the common clock framework, if you pass a NULL to
clk_get_rate, the function explicitly checks for it and returns 0. I
relied on that behaviour when implementing this; see the if..else block
above. Is this not always the case on other clock drivers?

That's something that the common clock framework decided to do.  It's
not a defined part of the API though, so drivers shouldn't rely on
this behaviour meaning anything special.