From: Robin Murphy <robin.murphy@arm.com>
To: Jacopo Mondi <jacopo+renesas@jmondi.org>,
ysato@users.sourceforge.jp, dalias@libc.org,
laurent.pinchart@ideasonboard.com, geert@linux-m68k.org
Cc: linux-renesas-soc@vger.kernel.org,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
linux-sh@vger.kernel.org
Subject: Re: [RFC v2 2/2] base: dma-mapping: Postpone page_to_pfn() on mmap()
Date: Wed, 15 Nov 2017 13:38:23 +0000 [thread overview]
Message-ID: <ea4f2d82-6a27-a7c1-091f-6230cfd988a3@arm.com> (raw)
In-Reply-To: <1510679286-6988-3-git-send-email-jacopo+renesas@jmondi.org>
On 14/11/17 17:08, Jacopo Mondi wrote:
> On SH4 architecture, with SPARSEMEM memory model, translating page to
> pfn hangs the CPU. Post-pone translation to pfn after
> dma_mmap_from_dev_coherent() function call as it succeeds and make page
> translation not necessary.
>
> This patch was suggested by Laurent Pinchart and he's working to submit
> a proper fix mainline. Not sending for inclusion at the moment.
Y'know, I think this patch does have some merit by itself - until we
know that cpu_addr *doesn't* represent some device-private memory which
is not guaranteed to be backed by a struct page, calling virt_to_page()
on it is arguably semantically incorrect, even if it might happen to be
benign in most cases.
Robin.
> Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> ---
> drivers/base/dma-mapping.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c
> index e584edd..73d64d3 100644
> --- a/drivers/base/dma-mapping.c
> +++ b/drivers/base/dma-mapping.c
> @@ -227,8 +227,8 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
> #ifndef CONFIG_ARCH_NO_COHERENT_DMA_MMAP
> unsigned long user_count = vma_pages(vma);
> unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> - unsigned long pfn = page_to_pfn(virt_to_page(cpu_addr));
> unsigned long off = vma->vm_pgoff;
> + unsigned long pfn;
>
> vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
>
> @@ -236,6 +236,7 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
> return ret;
>
> if (off < count && user_count <= (count - off)) {
> + pfn = page_to_pfn(virt_to_page(cpu_addr));
> ret = remap_pfn_range(vma, vma->vm_start,
> pfn + off,
> user_count << PAGE_SHIFT,
> --
> 2.7.4
>
> _______________________________________________
> iommu mailing list
> iommu@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu
>
next prev parent reply other threads:[~2017-11-15 13:38 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-14 17:08 [PATCH v2 0/2] Migo-R: reserve memory block with memblock APIs Jacopo Mondi
2017-11-14 17:08 ` Jacopo Mondi
2017-11-14 17:08 ` [PATCH v2 1/2] sh: migor: Reserve memory block for CEU Jacopo Mondi
2017-11-14 17:08 ` Jacopo Mondi
2017-11-14 17:08 ` [RFC v2 2/2] base: dma-mapping: Postpone page_to_pfn() on mmap() Jacopo Mondi
2017-11-14 17:08 ` Jacopo Mondi
2017-11-15 13:38 ` Robin Murphy [this message]
2018-04-09 7:25 ` jacopo mondi
2018-04-09 7:25 ` jacopo mondi
2018-04-09 11:11 ` Robin Murphy
2018-04-09 11:11 ` Robin Murphy
2018-04-09 11:11 ` Robin Murphy
2018-04-09 13:06 ` Laurent Pinchart
2018-04-09 13:06 ` Laurent Pinchart
2018-04-09 15:11 ` Rich Felker
2018-04-09 15:11 ` Rich Felker
2018-04-09 15:18 ` Laurent Pinchart
2018-04-09 15:18 ` Laurent Pinchart
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