linux-kernel - Re: [PATCH 3/4] rtc: rtc-jz4740: Use devm_ioremap

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Date:	Fri, 07 Feb 2014 09:49:22 +0100
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Jingoo Han <jg1.han@...sung.com>
CC:	'Andrew Morton' <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	'Alessandro Zummo' <a.zummo@...ertech.it>,
	rtc-linux@...glegroups.com,
	'Thierry Reding' <thierry.reding@...il.com>
Subject: Re: [PATCH 3/4] rtc: rtc-jz4740: Use devm_ioremap_resource()

On 02/07/2014 09:31 AM, Jingoo Han wrote:
> On Friday, February 07, 2014 5:13 PM, Lars-Peter Clausen wrote:
>> On 02/07/2014 08:58 AM, Jingoo Han wrote:
>> [...]
>>> -	rtc->base = devm_ioremap_nocache(&pdev->dev, rtc->mem->start,
>>> -					resource_size(rtc->mem));
>>> -	if (!rtc->base) {
>>> -		dev_err(&pdev->dev, "Failed to ioremap mmio memory\n");
>>> -		return -EBUSY;
>>> -	}
>>> +	mem->flags &= ~IORESOURCE_CACHEABLE;
>>
>> You shouldn't be modifying the resource, strictly speaking it is not owned
>> by the device. And IORESOURCE_CACHEABLE is never set for this device anyway.
>
> (+cc Thierry Reding)
>
> Hi Lars-Peter Clausen,
>
> Do you mean that resource's flags should NOT be modified by the
> device driver, right?
> Then, without 'mem->flags &= ~IORESOURCE_CACHEABLE', is it possible
> that devm_ioremap_nocache() can be called at devm_ioremap_resource()?
>

Yes. ioremap_nocache() will be called, when the flag is not set, 
ioremap_cached() will be called when the flag is set. If the flag is set the 
intention is probably that the region should be mapped cached.

> Thierry,
> Do you have any comments on this?
>
> Thank you.
>
> Best regards,
> Jingoo Han
>
>>
>>> +	rtc->base = devm_ioremap_resource(&pdev->dev, mem);
>>> +	if (IS_ERR(rtc->base))
>>> +		return PTR_ERR(rtc->base);
>>>
>>>    	spin_lock_init(&rtc->lock);
>>>
>>>
>

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