linux-kernel - Re: [PATCH 5/6] dma-mapping: Allow batched DMA sync operations if supported by the arch

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Message-ID: <20251225123650.GJ11869@unreal>
Date: Thu, 25 Dec 2025 14:36:50 +0200
From: Leon Romanovsky <leon@...nel.org>
To: Barry Song <21cnbao@...il.com>
Cc: ada.coupriediaz@....com, anshuman.khandual@....com, ardb@...nel.org,
	catalin.marinas@....com, iommu@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	m.szyprowski@...sung.com, maz@...nel.org, robin.murphy@....com,
	ryan.roberts@....com, surenb@...gle.com, v-songbaohua@...o.com,
	will@...nel.org, zhengtangquan@...o.com
Subject: Re: [PATCH 5/6] dma-mapping: Allow batched DMA sync operations if
 supported by the arch

On Thu, Dec 25, 2025 at 06:45:09PM +1300, Barry Song wrote:
> > > >
> > >
> > > OK. Could you take a look at [1] and see if any further
> > > improvements are needed before I send v2?
> >
> > Everything looks ok, except these renames:
> > -                       arch_sync_dma_for_cpu(paddr, sg->length, dir);
> > +                       arch_sync_dma_for_cpu_batch_add(paddr, sg->length, dir);
> 
> Thanks!
> I'm happy to drop the rename as outlined below-feedback welcome :-)
> 
> diff --git a/arch/arm64/include/asm/cache.h b/arch/arm64/include/asm/cache.h
> index dd2c8586a725..487fb7c355ed 100644
> --- a/arch/arm64/include/asm/cache.h
> +++ b/arch/arm64/include/asm/cache.h
> @@ -87,6 +87,12 @@ int cache_line_size(void);
>  
>  #define dma_get_cache_alignment	cache_line_size
>  
> +static inline void arch_sync_dma_flush(void)
> +{
> +	dsb(sy);
> +}
> +#define arch_sync_dma_flush arch_sync_dma_flush
> +
>  /* Compress a u64 MPIDR value into 32 bits. */
>  static inline u64 arch_compact_of_hwid(u64 id)
>  {
> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> index b2b5792b2caa..ae1ae0280eef 100644
> --- a/arch/arm64/mm/dma-mapping.c
> +++ b/arch/arm64/mm/dma-mapping.c
> @@ -17,7 +17,7 @@ void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
>  {
>  	unsigned long start = (unsigned long)phys_to_virt(paddr);
>  
> -	dcache_clean_poc(start, start + size);
> +	dcache_clean_poc_nosync(start, start + size);
>  }
>  
>  void arch_sync_dma_for_cpu(phys_addr_t paddr, size_t size,
> @@ -28,7 +28,7 @@ void arch_sync_dma_for_cpu(phys_addr_t paddr, size_t size,
>  	if (dir == DMA_TO_DEVICE)
>  		return;
>  
> -	dcache_inval_poc(start, start + size);
> +	dcache_inval_poc_nosync(start, start + size);
>  }
>  
>  void arch_dma_prep_coherent(struct page *page, size_t size)
> diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
> index 4809204c674c..e7dd8a63b40e 100644
> --- a/include/linux/dma-map-ops.h
> +++ b/include/linux/dma-map-ops.h
> @@ -361,6 +361,12 @@ static inline void arch_sync_dma_for_cpu(phys_addr_t paddr, size_t size,
>  }
>  #endif /* ARCH_HAS_SYNC_DMA_FOR_CPU */
>  
> +#ifndef arch_sync_dma_flush

You likely need to wrap this in "#ifdef CONFIG_ARCH_HAS_SYNC_DMA_FLUSH"
as done in the surrounding code.

Thanks

> +static inline void arch_sync_dma_flush(void)
> +{
> +}
> +#endif
> +
>  #ifdef CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL
>  void arch_sync_dma_for_cpu_all(void);
>  #else
>