[3/4] ARC: refactor arch/arc/mm/dma.c

Message ID 20180724101001.31965-4-Eugeniy.Paltsev@synopsys.com
State New
Headers show
Series
  • ARC: allow to use IOC and non-IOC DMA devices simultaneously
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Commit Message

Eugeniy Paltsev July 24, 2018, 10:10 a.m.
Refactoring, no functional change intended.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
---
 arch/arc/mm/dma.c | 28 ++++++++++------------------
 1 file changed, 10 insertions(+), 18 deletions(-)

Comments

Christoph Hellwig July 26, 2018, 9:17 a.m. | #1
On Tue, Jul 24, 2018 at 01:10:00PM +0300, Eugeniy Paltsev wrote:
> Refactoring, no functional change intended.

Might be worth explaining a bit why you are refactoring it (i.e. what is the
benefit).

> 
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
> ---
>  arch/arc/mm/dma.c | 28 ++++++++++------------------
>  1 file changed, 10 insertions(+), 18 deletions(-)
> 
> diff --git a/arch/arc/mm/dma.c b/arch/arc/mm/dma.c
> index b693818cd8e5..46584c7c2858 100644
> --- a/arch/arc/mm/dma.c
> +++ b/arch/arc/mm/dma.c
> @@ -27,30 +27,24 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
>  	struct page *page;
>  	phys_addr_t paddr;
>  	void *kvaddr;
> -	int need_coh = 1, need_kvaddr = 0;
> +	bool need_coh = !(attrs & DMA_ATTR_NON_CONSISTENT);
>  
>  	page = alloc_pages(gfp, order);
>  	if (!page)
>  		return NULL;
>  
>  	/* This is linear addr (0x8000_0000 based) */
>  	paddr = page_to_phys(page);
>  
>  	*dma_handle = paddr;
>  
> +	/*
> +	 * - A coherent buffer needs MMU mapping to enforce non-cachability
> +	 * - A highmem page needs a virtual handle (hence MMU mapping)
> +	 *   independent of cachability.
> +	 * kvaddr is kernel Virtual address (0x7000_0000 based)
> +	 */
> +	if (PageHighMem(page) || need_coh) {

dma_alloc_attrs clears __GFP_HIGHMEM from the passed in gfp mask, so
you'll never get a highmem page here.

That also means you can merge this conditional with the one for the cache
writeback and invalidation and kill the need_coh flag entirely.

>  		kvaddr = ioremap_nocache(paddr, size);
>  		if (kvaddr == NULL) {
>  			__free_pages(page, order);
> @@ -81,11 +75,9 @@ void arch_dma_free(struct device *dev, size_t size, void *vaddr,
>  {
>  	phys_addr_t paddr = dma_handle;
>  	struct page *page = virt_to_page(paddr);
> -	int is_non_coh = 1;
> -
> -	is_non_coh = (attrs & DMA_ATTR_NON_CONSISTENT);
> +	bool is_coh = !(attrs & DMA_ATTR_NON_CONSISTENT);
>  
> -	if (PageHighMem(page) || !is_non_coh)
> +	if (PageHighMem(page) || is_coh)
>  		iounmap((void __force __iomem *)vaddr);
>  

Same here.

Also if you clean this up it would be great to take the per-device pfn offset
into account, even if that isn't used anywhere on arc yet, that is call
phys_to_dma and dma_to_phys to convert to an from the dma address.
Eugeniy Paltsev July 30, 2018, 10:34 a.m. | #2
On Thu, 2018-07-26 at 11:17 +0200, Christoph Hellwig wrote:
> On Tue, Jul 24, 2018 at 01:10:00PM +0300, Eugeniy Paltsev wrote:
> > Refactoring, no functional change intended.
> >  
[snip]
> >  
> >  	*dma_handle = paddr;
> >  
> > +	/*
> > +	 * - A coherent buffer needs MMU mapping to enforce non-cachability
> > +	 * - A highmem page needs a virtual handle (hence MMU mapping)
> > +	 *   independent of cachability.
> > +	 * kvaddr is kernel Virtual address (0x7000_0000 based)
> > +	 */
> > +	if (PageHighMem(page) || need_coh) {
> 
> dma_alloc_attrs clears __GFP_HIGHMEM from the passed in gfp mask, so
> you'll never get a highmem page here.
> 

Nice catch, thanks.
Will remove check for highmem page in next patch version. 

> That also means you can merge this conditional with the one for the cache
> writeback and invalidation and kill the need_coh flag entirely.
> 
> >  		kvaddr = ioremap_nocache(paddr, size);
> >  		if (kvaddr == NULL) {
> >  			__free_pages(page, order);
> > @@ -81,11 +75,9 @@ void arch_dma_free(struct device *dev, size_t size, void *vaddr,
> >  {
> >  	phys_addr_t paddr = dma_handle;
> >  	struct page *page = virt_to_page(paddr);
> > -	int is_non_coh = 1;
> > -
> > -	is_non_coh = (attrs & DMA_ATTR_NON_CONSISTENT);
> > +	bool is_coh = !(attrs & DMA_ATTR_NON_CONSISTENT);
> >  
> > -	if (PageHighMem(page) || !is_non_coh)
> > +	if (PageHighMem(page) || is_coh)
> >  		iounmap((void __force __iomem *)vaddr);
> >  
> 
> Same here.
> 
> Also if you clean this up it would be great to take the per-device pfn offset
> into account, even if that isn't used anywhere on arc yet, that is call
> phys_to_dma and dma_to_phys to convert to an from the dma address.

Ok, I'll look at it.
Probably I'll implement it as a separate patch as it is irrelevant to this
patch series topic.

Patch

diff --git a/arch/arc/mm/dma.c b/arch/arc/mm/dma.c
index b693818cd8e5..46584c7c2858 100644
--- a/arch/arc/mm/dma.c
+++ b/arch/arc/mm/dma.c
@@ -27,30 +27,24 @@  void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 	struct page *page;
 	phys_addr_t paddr;
 	void *kvaddr;
-	int need_coh = 1, need_kvaddr = 0;
+	bool need_coh = !(attrs & DMA_ATTR_NON_CONSISTENT);
 
 	page = alloc_pages(gfp, order);
 	if (!page)
 		return NULL;
 
-	if (attrs & DMA_ATTR_NON_CONSISTENT)
-		need_coh = 0;
-
-	/*
-	 * - A coherent buffer needs MMU mapping to enforce non-cachability
-	 * - A highmem page needs a virtual handle (hence MMU mapping)
-	 *   independent of cachability
-	 */
-	if (PageHighMem(page) || need_coh)
-		need_kvaddr = 1;
-
 	/* This is linear addr (0x8000_0000 based) */
 	paddr = page_to_phys(page);
 
 	*dma_handle = paddr;
 
-	/* This is kernel Virtual address (0x7000_0000 based) */
-	if (need_kvaddr) {
+	/*
+	 * - A coherent buffer needs MMU mapping to enforce non-cachability
+	 * - A highmem page needs a virtual handle (hence MMU mapping)
+	 *   independent of cachability.
+	 * kvaddr is kernel Virtual address (0x7000_0000 based)
+	 */
+	if (PageHighMem(page) || need_coh) {
 		kvaddr = ioremap_nocache(paddr, size);
 		if (kvaddr == NULL) {
 			__free_pages(page, order);
@@ -81,11 +75,9 @@  void arch_dma_free(struct device *dev, size_t size, void *vaddr,
 {
 	phys_addr_t paddr = dma_handle;
 	struct page *page = virt_to_page(paddr);
-	int is_non_coh = 1;
-
-	is_non_coh = (attrs & DMA_ATTR_NON_CONSISTENT);
+	bool is_coh = !(attrs & DMA_ATTR_NON_CONSISTENT);
 
-	if (PageHighMem(page) || !is_non_coh)
+	if (PageHighMem(page) || is_coh)
 		iounmap((void __force __iomem *)vaddr);
 
 	__free_pages(page, get_order(size));