Subject: [PATCH v4 3/6] of: fix size when dma-range is not used

From: [email-masked] (Murali Karicheri)
Date: Fri, 30 Jan 2015 13:06:27 -0500

On 01/28/2015 12:30 PM, Catalin Marinas wrote:
> On Wed, Jan 28, 2015 at 03:55:57PM +0000, Robin Murphy wrote:
>> On 28/01/15 11:05, Catalin Marinas wrote:
>>> On Tue, Jan 27, 2015 at 06:55:15PM +0000, Murali Karicheri wrote:
>>>> How about having the logic like this?
>>>>
>>>> 	ret = of_dma_get_range(np,&dma_addr,&paddr,&size);
>>>> 	if (ret<  0) {
>>>> 		dma_addr = offset = 0;
>>>> 		size = dev->coherent_dma_mask + 1;
>>>> 	} else {
>>>> 		offset = PFN_DOWN(paddr - dma_addr);
>>>> 		dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset);
>>>> 	}
>>>>
>>>> 	if (is_power_of_2(size + 1))
>>>> 		size = size + 1;
>>>> 	else if (!is_power_of_2(size))
>>>> 	{
>>>> 		dev_err(dev, "invalid size\n");
>>>> 		return;
>>>> 	}
>>>
>>> In of_dma_configure(), we currently assume that the default coherent
>>> mask is 32-bit. In this thread:
>>>
>>> http://article.gmane.org/gmane.linux.kernel/1835096
>>>
>>> we talked about setting the coherent mask based on size automatically.
>>> I'm not sure about the size but I think we can assume is 32-bit mask + 1
>>> if it is not specified in the DT. Instead of just assuming a default
>>> mask, let's assume a default size and create the mask based on this
>>> (untested):
>>>
>>> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
>>> index 5b33c6a21807..9ff8d1286b44 100644
>>> --- a/drivers/of/platform.c
>>> +++ b/drivers/of/platform.c
>>> @@ -170,10 +170,10 @@ static void of_dma_configure(struct device *dev)
>>>    	struct iommu_ops *iommu;
>>>
>>>    	/*
>>> -	 * Set default dma-mask to 32 bit. Drivers are expected to setup
>>> -	 * the correct supported dma_mask.
>>> +	 * Set default size to cover the 32-bit. Drivers are expected to setup
>>> +	 * the correct size and dma_mask.
>>>    	 */
>>> -	dev->coherent_dma_mask = DMA_BIT_MASK(32);
>>> +	size = 1ULL<<  32;
>>>
>>>    	/*
>>>    	 * Set it to coherent_dma_mask by default if the architecture
>>> @@ -185,13 +185,24 @@ static void of_dma_configure(struct device *dev)
>>>    	ret = of_dma_get_range(dev->of_node,&dma_addr,&paddr,&size);
>>>    	if (ret<  0) {
>>>    		dma_addr = offset = 0;
>>> -		size = dev->coherent_dma_mask;
>>>    	} else {
>>>    		offset = PFN_DOWN(paddr - dma_addr);
>>>    		dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", dev->dma_pfn_offset);
>>>    	}
>>>    	dev->dma_pfn_offset = offset;
>>>
>>> +	/*
>>> +	 * Workaround for DTs setting the size to a mask or 0.
>>> +	 */
>>> +	if (is_power_of_2(size + 1))
>>> +		size += 1;
>>
>> In fact, since the ilog2 below ends up effectively rounding down, we
>> might as well do away with this check as well and just add 1
>> unconditionally. The only time it makes any difference is when we want
>> it to anyway!
>
> Well, we could simply ignore the is_power_of_2() check but without
> incrementing size as we don't know what arch_setup_dma_ops() does with
> it.
>
> I think we can remove this check altogether (we leaved without it for a
> while) but we need to add 1 when calculating the mask:
>
> 	dev->coherent_dma_mask = min(DMA_BIT_MASK(32),
> 				     DMA_BIT_MASK(ilog2(size + 1)));
>
For Keystone, the dma_addr is to be taken care as well to determine the 
mask. The above will not work.

Based on the discussion so far, this is the function I have come up with 
incorporating the suggestions. Please review this and see if I have 
missed out any. This works fine on Keystone.

void of_dma_configure(struct device *dev, struct device_node *np)
{
	u64 dma_addr = 0, paddr, size;
	int ret;
	bool coherent;
	unsigned long offset = 0;
	struct iommu_ops *iommu;

	/*
	 * Set default size to cover the 32-bit. Drivers are expected to setup
	 * the correct size and dma_mask.
   	 */
	size = 1ULL << 32;

	ret = of_dma_get_range(np, &dma_addr, &paddr, &size);
	if (!ret) {
		offset = PFN_DOWN(paddr - dma_addr);
		if (!size) {
			dev_err(dev, "Invalid size (%llx)\n",
				size);
			return;
		}
		if (size & 1) {
			size = size + 1;
			dev_warn(dev, "Incorrect usage of size (%llx)\n",
				 size);
		}
		dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset);
	}
	dev->dma_pfn_offset = offset;

	/*
	 * Coherent DMA masks larger than 32-bit must be explicitly set by the
	 * driver.
	 */
	dev->coherent_dma_mask = min(DMA_BIT_MASK(32),
				     DMA_BIT_MASK(ilog2(dma_addr + size)));
	/*
	 * Set dma_mask to coherent_dma_mask by default if the architecture
	 * code has not set it.
	 */
	if (!dev->dma_mask)
		dev->dma_mask = &dev->coherent_dma_mask;

	coherent = of_dma_is_coherent(np);
	dev_dbg(dev, "device is%sdma coherent\n",
		coherent ? " " : " not ");

	iommu = of_iommu_configure(dev, np);
	dev_dbg(dev, "device is%sbehind an iommu\n",
		iommu ? " " : " not ");

	arch_setup_dma_ops(dev, dma_addr, size, iommu, coherent);
}

-- 
Murali Karicheri
Linux Kernel, Texas Instruments