linux-kernel - Re: [PATCHv6 2/8] dma-debug: add support for resource mappings

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Date:	Thu, 19 May 2016 12:42:04 +0100
From:	Robin Murphy <robin.murphy@....com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	vinod.koul@...el.com, linux-renesas-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	dmaengine@...r.kernel.org, iommu@...ts.linux-foundation.org,
	hch@...radead.org, linux-arch@...r.kernel.org,
	geert+renesas@...der.be, arnd@...db.de, linus.walleij@...aro.org,
	laurent.pinchart@...asonboard.com, dan.j.williams@...el.com
Subject: Re: [PATCHv6 2/8] dma-debug: add support for resource mappings

On 19/05/16 12:21, Niklas Söderlund wrote:
> Hi Konrad,
>
> Thanks for your feedback.
>
> On 2016-05-17 10:50:02 -0400, Konrad Rzeszutek Wilk wrote:
>>> +void debug_dma_map_resource(struct device *dev, phys_addr_t addr, size_t size,
>>> +			    int direction, dma_addr_t dma_addr)
>>> +{
>>> +	struct dma_debug_entry *entry;
>>> +
>>> +	if (unlikely(dma_debug_disabled()))
>>> +		return;
>>> +
>>> +	entry = dma_entry_alloc();
>>> +	if (!entry)
>>> +		return;
>>> +
>>> +	entry->type		= dma_debug_resource;
>>> +	entry->dev		= dev;
>>> +	entry->pfn		= __phys_to_pfn(addr);
>>> +	entry->offset		= addr - PHYS_PFN(entry->pfn);
>>
>> Is that right?
>
> You are correct that should be:
>
>     entry->offset = addr - PFN_PHYS(entry->pfn);
>
> Or even better:
>
>     entry->offset = addr - __pfn_to_phys(entry->pfn);

Better still, simply offset_in_page(addr) (as per dma_map_single()).

Robin.

> I will address this and resend late next week, still hoping for some
> more feedback.
>
>>
>> __phys_to_pfn(addr) is PHYS_PFN(addr), so what you get here is
>>
>> addr - PHYS_PFN(PHYS_PFN(addr)) ?
>>
>>
>>> +	entry->size		= size;
>>> +	entry->dev_addr		= dma_addr;
>>> +	entry->direction	= direction;
>>> +	entry->map_err_type	= MAP_ERR_NOT_CHECKED;
>>> +
>>> +	add_dma_entry(entry);
>>> +}
>>> +EXPORT_SYMBOL(debug_dma_map_resource);
>>> +
>