Re: [PATCH 5/7] dma-direct: handle DMA_ATTR_NON_CONSISTENT in common code

[Hillf Danton <hdanton@sina.com>]

Hello Christoph

On Fri, 14 Jun 2019 16:44:29 +0200 Christoph Hellwig wrote:
> Only call into arch_dma_alloc if we require an uncached mapping,
> and remove the parisc code manually doing normal cached
> DMA_ATTR_NON_CONSISTENT allocations.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  arch/parisc/kernel/pci-dma.c | 48 ++++++++++--------------------------
>  kernel/dma/direct.c          |  4 +--
>  2 files changed, 15 insertions(+), 37 deletions(-)
> 
> diff --git a/arch/parisc/kernel/pci-dma.c b/arch/parisc/kernel/pci-dma.c
> index 239162355b58..ca35d9a76e50 100644
> --- a/arch/parisc/kernel/pci-dma.c
> +++ b/arch/parisc/kernel/pci-dma.c
> @@ -394,17 +394,20 @@ pcxl_dma_init(void)
>  
>  __initcall(pcxl_dma_init);
>  
> -static void *pcxl_dma_alloc(struct device *dev, size_t size,
> -		dma_addr_t *dma_handle, gfp_t flag, unsigned long attrs)
> +void *arch_dma_alloc(struct device *dev, size_t size,
> +		dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs)
>  {
>  	unsigned long vaddr;
>  	unsigned long paddr;
>  	int order;
>  
> +	if (boot_cpu_data.cpu_type != pcxl2 && boot_cpu_data.cpu_type != pcxl)
> +		return NULL;
> +
Literally, any cpu (call it cpuW) other than pcx12 and pcx1 will no longer do
dma alloc for any device with this patch applied. On the other hand, 
!dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_NON_CONSISTENT) will ask
any cpu to do dma alloc, regardless of pcx1. This patch works imo unless cpuW
plays games only with devices that are dma coherent. I doubt it is true.

--
Hillf
>  	order = get_order(size);
>  	size = 1 << (order + PAGE_SHIFT);
>  	vaddr = pcxl_alloc_range(size);
> -	paddr = __get_free_pages(flag | __GFP_ZERO, order);
> +	paddr = __get_free_pages(gfp | __GFP_ZERO, order);
>  	flush_kernel_dcache_range(paddr, size);
>  	paddr = __pa(paddr);
>  	map_uncached_pages(vaddr, size, paddr);
> @@ -421,44 +424,19 @@ static void *pcxl_dma_alloc(struct device *dev, size_t size,
>  	return (void *)vaddr;
>  }
>  
> -static void *pcx_dma_alloc(struct device *dev, size_t size,
> -		dma_addr_t *dma_handle, gfp_t flag, unsigned long attrs)
> -{
> -	void *addr;
> -
> -	if ((attrs & DMA_ATTR_NON_CONSISTENT) == 0)
> -		return NULL;
> -
> -	addr = (void *)__get_free_pages(flag | __GFP_ZERO, get_order(size));
> -	if (addr)
> -		*dma_handle = (dma_addr_t)virt_to_phys(addr);
> -
> -	return addr;
> -}
> -
> -void *arch_dma_alloc(struct device *dev, size_t size,
> -		dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs)
> -{
> -
> -	if (boot_cpu_data.cpu_type == pcxl2 || boot_cpu_data.cpu_type == pcxl)
> -		return pcxl_dma_alloc(dev, size, dma_handle, gfp, attrs);
> -	else
> -		return pcx_dma_alloc(dev, size, dma_handle, gfp, attrs);
> -}
> -
>  void arch_dma_free(struct device *dev, size_t size, void *vaddr,
>  		dma_addr_t dma_handle, unsigned long attrs)
>  {
>  	int order = get_order(size);
>  
> -	if (boot_cpu_data.cpu_type == pcxl2 || boot_cpu_data.cpu_type == pcxl) {
> -		size = 1 << (order + PAGE_SHIFT);
> -		unmap_uncached_pages((unsigned long)vaddr, size);
> -		pcxl_free_range((unsigned long)vaddr, size);
> +	WARN_ON_ONCE(boot_cpu_data.cpu_type != pcxl2 &&
> +		     boot_cpu_data.cpu_type != pcxl);
>  
> -		vaddr = __va(dma_handle);
> -	}
> -	free_pages((unsigned long)vaddr, get_order(size));
> +	size = 1 << (order + PAGE_SHIFT);
> +	unmap_uncached_pages((unsigned long)vaddr, size);
> +	pcxl_free_range((unsigned long)vaddr, size);
> +
> +	free_pages((unsigned long)__va(dma_handle), order);
>  }
>  
>  void arch_sync_dma_for_device(struct device *dev, phys_addr_t paddr,
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index c2893713bf80..fc354f4f490b 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -191,7 +191,7 @@ void *dma_direct_alloc(struct device *dev, size_t size,
>  		dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs)
>  {
>  	if (!IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) &&
> -	    !dev_is_dma_coherent(dev))
> +	    dma_alloc_need_uncached(dev, attrs))
>  		return arch_dma_alloc(dev, size, dma_handle, gfp, attrs);
>  	return dma_direct_alloc_pages(dev, size, dma_handle, gfp, attrs);
>  }
> @@ -200,7 +200,7 @@ void dma_direct_free(struct device *dev, size_t size,
>  		void *cpu_addr, dma_addr_t dma_addr, unsigned long attrs)
>  {
>  	if (!IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) &&
> -	    !dev_is_dma_coherent(dev))
> +	    dma_alloc_need_uncached(dev, attrs))
>  		arch_dma_free(dev, size, cpu_addr, dma_addr, attrs);
>  	else
>  		dma_direct_free_pages(dev, size, cpu_addr, dma_addr, attrs);
> -- 
> 2.20.1
> 



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