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

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Message-ID: <5743BCF5.8030607@rock-chips.com>
Date:	Tue, 24 May 2016 10:31:17 +0800
From:	Shunqian Zheng <zhengsq@...k-chips.com>
To:	Catalin Marinas <catalin.marinas@....com>,
	Robin Murphy <robin.murphy@....com>
CC:	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

Catalin, Robin,

On 2016年05月23日 21:35, Catalin Marinas wrote:
> 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.
It's easier for us if changing  the __dma_flush_range() to 
__flush_dcache_area() is acceptable here?

Thank you,
- shunqian
> I fully agree, these functions should not be used in drivers.