linux-kernel - Re: [PATCH V6 07/33] csky: MMU and page table management

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Message-ID: <20180929170415.GD27796@guoren-Inspiron-7460>
Date:   Sun, 30 Sep 2018 01:04:16 +0800
From:   Guo Ren <ren_guo@...ky.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     akpm@...ux-foundation.org, arnd@...db.de,
        daniel.lezcano@...aro.org, davem@...emloft.net,
        gregkh@...uxfoundation.org, jason@...edaemon.net,
        marc.zyngier@....com, mark.rutland@....com,
        mchehab+samsung@...nel.org, peterz@...radead.org, robh@...nel.org,
        robh+dt@...nel.org, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        devicetree@...r.kernel.org, green.hu@...il.com
Subject: Re: [PATCH V6 07/33] csky: MMU and page table management

On Thu, Sep 27, 2018 at 08:47:33AM -0700, Christoph Hellwig wrote:
> > +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)
OK, I like 2th.

> > +	if (DMA_ATTR_NON_CONSISTENT & attrs)
> > +		BUG();
> 
> Please don't bug on unknown attributs, they can be safely ignored.
No BUG(), return NULL.

> 
> > +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.
Ops ... BIG BUG, must be fixed immediately, thank you.

Best Regards
 Guo Ren