linux-kernel - Re: [PATCH v6 3/7] of: fix size when dma-range is not used

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Date:	Fri, 6 Feb 2015 15:26:55 -0500
From:	Murali Karicheri <m-karicheri2@...com>
To:	Catalin Marinas <catalin.marinas@....com>
CC:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>, Joerg Roedel <joro@...tes.org>,
	Will Deacon <Will.Deacon@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>
Subject: Re: [PATCH v6 3/7] of: fix size when dma-range is not used

On 02/06/2015 10:12 AM, Catalin Marinas wrote:
> On Fri, Feb 06, 2015 at 02:54:23PM +0000, Murali Karicheri wrote:
>> On 02/06/2015 09:38 AM, Catalin Marinas wrote:
>>> On Thu, Feb 05, 2015 at 09:52:55PM +0000, Murali Karicheri wrote:
>>>> Fix the dma-range size when the DT attribute is missing. i.e  set size to
>>>> dev->coherent_dma_mask + 1 instead of dev->coherent_dma_mask. Also add
>>>> code to check invalid values of size configured in DT and log error.
>>>>
>>>> Cc: Joerg Roedel<joro@...tes.org>
>>>> Cc: Grant Likely<grant.likely@...aro.org>
>>>> Cc: Rob Herring<robh+dt@...nel.org>
>>>> Cc: Bjorn Helgaas<bhelgaas@...gle.com>
>>>> Cc: Will Deacon<will.deacon@....com>
>>>> Cc: Russell King<linux@....linux.org.uk>
>>>> Cc: Arnd Bergmann<arnd@...db.de>
>>>> Cc: Suravee Suthikulpanit<Suravee.Suthikulpanit@....com>
>>>>
>>>> Signed-off-by: Murali Karicheri<m-karicheri2@...com>
>>>> ---
>>>>    drivers/of/device.c |   17 ++++++++++++++++-
>>>>    1 file changed, 16 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/of/device.c b/drivers/of/device.c
>>>> index 2de320d..314c8a9 100644
>>>> --- a/drivers/of/device.c
>>>> +++ b/drivers/of/device.c
>>>> @@ -105,9 +105,24 @@ void of_dma_configure(struct device *dev, struct device_node *np)
>>>>    	ret = of_dma_get_range(np,&dma_addr,&paddr,&size);
>>>>    	if (ret<   0) {
>>>>    		dma_addr = offset = 0;
>>>> -		size = dev->coherent_dma_mask;
>>>> +		size = dev->coherent_dma_mask + 1;
>>>>    	} else {
>>>>    		offset = PFN_DOWN(paddr - dma_addr);
>>>> +
>>>> +		/*
>>>> +		 * Add a work around to treat the size as mask + 1 in case
>>>> +		 * it is defined in DT as a mask.
>>>> +		 */
>>>> +		if (size&   1) {
>>>> +			dev_warn(dev, "Invalid size 0x%llx for dma-range\n",
>>>> +				 size);
>>>> +			size = size + 1;
>>>> +		}
>>>> +
>>>> +		if (!size) {
>>>> +			dev_err(dev, "Adjusted size 0x%llx invalid\n", size);
>>>> +			return;
>>>> +		}
>>>
>>> Would it make sense to set coherent_dma_mask to 0 here to make this more
>>> noticeable? It can be done together with the mask calculation from size.
>>
>> I guess you are the following in the code.
>>
>> if (!size) {
>> 		dev->coherent_dma_mask = 0;
>> 		dev_err(dev, "Adjusted size 0x%llx invalid\n", size);
>> 		return;
>> }
>>
>> Not sure how this is going to help and how this get handled by the
>> caller and subsequent logic. Probably it will cause probe to fail, with
>> some helpful error code.
>
> Not sure how it will fail, maybe the driver figures out that DMA isn't
> available and say something or switch to PIO. I guess you can leave it
> as 32-bit mask by default for now even in case of size == 0.
>
> BTW, since pci_device_add() already sets coherent_dma_mask, you could
> add another check at the beginning of of_dma_configure():
>
> 	if (!dev->coherent_dma_mask)
> 		dev->coherent_dma_mask = DMA_BIT_MASK(32);
>
> That's more of a nitpick as the values are both the same.
>
Catalin,

Just posted a patch for size based dma mask with title "of: calculate 
masks of the device based on dma-range size". Please review and comment

-- 
Murali Karicheri
Linux Kernel, Texas Instruments
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