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

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Message-ID: <5742DEFE.1040902@arm.com>
Date:	Mon, 23 May 2016 11:44:14 +0100
From:	Robin Murphy <robin.murphy@....com>
To:	Shunqian Zheng <zhengsq@...k-chips.com>, joro@...tes.org,
	heiko@...ech.de, Catalin Marinas <Catalin.Marinas@....com>,
	Mark Rutland <mark.rutland@....com>
Cc:	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 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.

Robin.

>   }
>
>   static struct rk_iommu_domain *to_rk_domain(struct iommu_domain *dom)
>