[PATCH 1/6] serial: 8250_dw: add support for clk api

Emilio López
2013-03-16T00:40:47Z

El 15/03/13 21:29, Russell King - ARM Linux escribi?:
> 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?:
>>> On Fri, Mar 15, 2013 at 09:06:23PM +0100, Maxime Ripard wrote:
>>>> + /* 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.
>
>>>> + 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
>>
>>>> +
>>>> 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.

Ok then, I'll rework the error checking on the clock calls and get a new
patch sent. Thanks for the clarification.

Emilio