linux-kernel - Re: [PATCH 4/5] iommu/rockchip: add ARM64 cache flush operation for iommu

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Message-ID: <20160523133500.GF4892@e104818-lin.cambridge.arm.com>
Date:	Mon, 23 May 2016 14:35:00 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Robin Murphy <robin.murphy@....com>
Cc:	Shunqian Zheng <zhengsq@...k-chips.com>, joro@...tes.org,
	heiko@...ech.de, Mark Rutland <mark.rutland@....com>,
	linux-rockchip@...ts.infradead.org,
	iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Simon <xxm@...k-chips.com>
Subject: Re: [PATCH 4/5] iommu/rockchip: add ARM64 cache flush operation for
 iommu

On Mon, May 23, 2016 at 11:44:14AM +0100, Robin Murphy wrote:
> On 23/05/16 02:37, Shunqian Zheng wrote:
> >From: Simon <xxm@...k-chips.com>
> >
> >Signed-off-by: Simon <xxm@...k-chips.com>
> >---
> >  drivers/iommu/rockchip-iommu.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> >diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
> >index 043d18c..1741b65 100644
> >--- a/drivers/iommu/rockchip-iommu.c
> >+++ b/drivers/iommu/rockchip-iommu.c
> >@@ -95,12 +95,16 @@ struct rk_iommu {
> >
> >  static inline void rk_table_flush(u32 *va, unsigned int count)
> >  {
> >+#if defined(CONFIG_ARM)
> >  	phys_addr_t pa_start = virt_to_phys(va);
> >  	phys_addr_t pa_end = virt_to_phys(va + count);
> >  	size_t size = pa_end - pa_start;
> >
> >  	__cpuc_flush_dcache_area(va, size);
> >  	outer_flush_range(pa_start, pa_end);
> >+#elif defined(CONFIG_ARM64)
> >+	__dma_flush_range(va, va + count);
> >+#endif
> 
> Ugh, please don't use arch-private cache maintenance functions directly from
> a driver. Allocating/mapping page tables to be read by the IOMMU is still
> DMA, so using the DMA APIs is the correct way to manage them, *especially*
> if it needs to work across multiple architectures.

I fully agree, these functions should not be used in drivers.

-- 
Catalin