From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH V6 07/33] csky: MMU and page table management
Date: Thu, 27 Sep 2018 08:47:33 -0700
Message-ID: <20180927154733.GA15985@infradead.org>
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To: Guo Ren <ren_guo@c-sky.com>
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> +static void *csky_dma_alloc_atomic(
> +	struct device *dev,
> +	size_t size,
> +	dma_addr_t *dma_handle
> +	)

Can you please use normal kernel coding style?  Closing brace on the
same line, either two tab indents for the arguments or align them to the
first argument:

static void *csky_dma_alloc_atomic(struct device *dev, size_t size,
		dma_addr_t *dma_handle)

or:

static void *csky_dma_alloc_atomic(struct device *dev, size_t size,
				   dma_addr_t *dma_handle)

> +	if (DMA_ATTR_NON_CONSISTENT & attrs)
> +		BUG();

Please don't bug on unknown attributs, they can be safely ignored.

> +void arch_sync_dma_for_device(struct device *dev, phys_addr_t paddr,
> +			      size_t size, enum dma_data_direction dir)
> +{
> +	struct page *page = pfn_to_page(paddr >> PAGE_SHIFT);
> +	unsigned long offset = paddr & ~PAGE_MASK;
> +	unsigned long vaddr;
> +
> +	if (PageHighMem(page))
> +		vaddr = (unsigned long) kmap_atomic(page);

This isn't going to work as the size might be larger than PAGE_SIZE.