[PATCH v6 1/2] ARM: dma-mapping: Don't use outer_flush_range when the L2C is coherent

[PATCH v6 1/2] ARM: dma-mapping: Don't use outer_flush_range when the L2C is coherent

[Gregory CLEMENT]

When a L2 cache controller is used in a system that provides hardware
coherency, the entire outer cache operations are useless, and can be
skipped.  Moreover, on some systems, it is harmful as it causes
deadlocks between the Marvell coherency mechanism, the Marvell PCIe
controller and the Cortex-A9.

In the current kernel implementation, the outer cache flush range
operation is triggered by the dma_alloc function.
This operation can be take place during runtime and in some
circumstances may lead to the PCIe/PL310 deadlock on Armada 375/38x
SoCs.

This patch extends the __dma_clear_buffer() function to receive a
boolean argument related to the coherency of the system. The same
things is done for the calling functions.

Reported-by: Nadav Haklai <nadavh@marvell.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Cc: <stable@vger.kernel.org> # v3.16+
---
 arch/arm/mm/dma-mapping.c | 63 +++++++++++++++++++++++++++++------------------
 1 file changed, 39 insertions(+), 24 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index deac58d5f1f7..1538bb293e90 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -61,7 +61,7 @@ struct arm_dma_free_args {
 
 struct arm_dma_allocator {
 	void *(*alloc)(struct arm_dma_alloc_args *args,
-		       struct page **ret_page);
+		       struct page **ret_page, bool is_coherent);
 	void (*free)(struct arm_dma_free_args *args);
 };
 
@@ -274,7 +274,7 @@ static u64 get_coherent_dma_mask(struct device *dev)
 	return mask;
 }
 
-static void __dma_clear_buffer(struct page *page, size_t size)
+static void __dma_clear_buffer(struct page *page, size_t size, bool is_coherent)
 {
 	/*
 	 * Ensure that the allocated pages are zeroed, and that any data
@@ -291,12 +291,14 @@ static void __dma_clear_buffer(struct page *page, size_t size)
 			page++;
 			size -= PAGE_SIZE;
 		}
-		outer_flush_range(base, end);
+		if (!is_coherent)
+			outer_flush_range(base, end);
 	} else {
 		void *ptr = page_address(page);
 		memset(ptr, 0, size);
 		dmac_flush_range(ptr, ptr + size);
-		outer_flush_range(__pa(ptr), __pa(ptr) + size);
+		if (!is_coherent)
+			outer_flush_range(__pa(ptr), __pa(ptr) + size);
 	}
 }
 
@@ -304,7 +306,8 @@ static void __dma_clear_buffer(struct page *page, size_t size)
  * Allocate a DMA buffer for 'dev' of size 'size' using the
  * specified gfp mask.  Note that 'size' must be page aligned.
  */
-static struct page *__dma_alloc_buffer(struct device *dev, size_t size, gfp_t gfp)
+static struct page *__dma_alloc_buffer(struct device *dev, size_t size,
+				       gfp_t gfp, bool is_coherent)
 {
 	unsigned long order = get_order(size);
 	struct page *page, *p, *e;
@@ -320,7 +323,7 @@ static struct page *__dma_alloc_buffer(struct device *dev, size_t size, gfp_t gf
 	for (p = page + (size >> PAGE_SHIFT), e = page + (1 << order); p < e; p++)
 		__free_page(p);
 
-	__dma_clear_buffer(page, size);
+	__dma_clear_buffer(page, size, is_coherent);
 
 	return page;
 }
@@ -342,7 +345,8 @@ static void __dma_free_buffer(struct page *page, size_t size)
 
 static void *__alloc_from_contiguous(struct device *dev, size_t size,
 				     pgprot_t prot, struct page **ret_page,
-				     const void *caller, bool want_vaddr);
+				     const void *caller, bool want_vaddr,
+				     bool is_coherent);
 
 static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t gfp,
 				 pgprot_t prot, struct page **ret_page,
@@ -407,10 +411,13 @@ static int __init atomic_pool_init(void)
 	atomic_pool = gen_pool_create(PAGE_SHIFT, -1);
 	if (!atomic_pool)
 		goto out;
-
+	/*
+	 * The atomic pool is only used for non-coherent allocations
+	 * so we must pass false for is_coherent.
+	 */
 	if (dev_get_cma_area(NULL))
 		ptr = __alloc_from_contiguous(NULL, atomic_pool_size, prot,
-					      &page, atomic_pool_init, true);
+				      &page, atomic_pool_init, true, false);
 	else
 		ptr = __alloc_remap_buffer(NULL, atomic_pool_size, gfp, prot,
 					   &page, atomic_pool_init, true);
@@ -524,7 +531,11 @@ static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t gfp,
 {
 	struct page *page;
 	void *ptr = NULL;
-	page = __dma_alloc_buffer(dev, size, gfp);
+	/*
+	 * __alloc_remap_buffer is only called when the device is
+	 * non-coherent
+	 */
+	page = __dma_alloc_buffer(dev, size, gfp, false);
 	if (!page)
 		return NULL;
 	if (!want_vaddr)
@@ -579,7 +590,8 @@ static int __free_from_pool(void *start, size_t size)
 
 static void *__alloc_from_contiguous(struct device *dev, size_t size,
 				     pgprot_t prot, struct page **ret_page,
-				     const void *caller, bool want_vaddr)
+				     const void *caller, bool want_vaddr,
+				     bool is_coherent)
 {
 	unsigned long order = get_order(size);
 	size_t count = size >> PAGE_SHIFT;
@@ -590,7 +602,7 @@ static void *__alloc_from_contiguous(struct device *dev, size_t size,
 	if (!page)
 		return NULL;
 
-	__dma_clear_buffer(page, size);
+	__dma_clear_buffer(page, size, is_coherent);
 
 	if (!want_vaddr)
 		goto out;
@@ -640,7 +652,7 @@ static inline pgprot_t __get_dma_pgprot(struct dma_attrs *attrs, pgprot_t prot)
 #define __get_dma_pgprot(attrs, prot)				__pgprot(0)
 #define __alloc_remap_buffer(dev, size, gfp, prot, ret, c, wv)	NULL
 #define __alloc_from_pool(size, ret_page)			NULL
-#define __alloc_from_contiguous(dev, size, prot, ret, c, wv)	NULL
+#define __alloc_from_contiguous(dev, size, prot, ret, c, wv, is_coherent)	NULL
 #define __free_from_pool(cpu_addr, size)			do { } while (0)
 #define __free_from_contiguous(dev, page, cpu_addr, size, wv)	do { } while (0)
 #define __dma_free_remap(cpu_addr, size)			do { } while (0)
@@ -651,7 +663,8 @@ static void *__alloc_simple_buffer(struct device *dev, size_t size, gfp_t gfp,
 				   struct page **ret_page)
 {
 	struct page *page;
-	page = __dma_alloc_buffer(dev, size, gfp);
+	/* __alloc_simple_buffer is only called when the device is coherent */
+	page = __dma_alloc_buffer(dev, size, gfp, true);
 	if (!page)
 		return NULL;
 
@@ -660,7 +673,7 @@ static void *__alloc_simple_buffer(struct device *dev, size_t size, gfp_t gfp,
 }
 
 static void *simple_allocator_alloc(struct arm_dma_alloc_args *args,
-				    struct page **ret_page)
+				    struct page **ret_page, bool is_coherent)
 {
 	return __alloc_simple_buffer(args->dev, args->size, args->gfp,
 				     ret_page);
@@ -677,11 +690,11 @@ static struct arm_dma_allocator simple_allocator = {
 };
 
 static void *cma_allocator_alloc(struct arm_dma_alloc_args *args,
-				 struct page **ret_page)
+				 struct page **ret_page, bool is_coherent)
 {
 	return __alloc_from_contiguous(args->dev, args->size, args->prot,
 				       ret_page, args->caller,
-				       args->want_vaddr);
+				       args->want_vaddr, is_coherent);
 }
 
 static void cma_allocator_free(struct arm_dma_free_args *args)
@@ -696,7 +709,7 @@ static struct arm_dma_allocator cma_allocator = {
 };
 
 static void *pool_allocator_alloc(struct arm_dma_alloc_args *args,
-				  struct page **ret_page)
+				  struct page **ret_page, bool is_coherent)
 {
 	return __alloc_from_pool(args->size, ret_page);
 }
@@ -712,7 +725,7 @@ static struct arm_dma_allocator pool_allocator = {
 };
 
 static void *remap_allocator_alloc(struct arm_dma_alloc_args *args,
-				   struct page **ret_page)
+				   struct page **ret_page, bool is_coherent)
 {
 	return __alloc_remap_buffer(args->dev, args->size, args->gfp,
 				    args->prot, ret_page, args->caller,
@@ -792,7 +805,7 @@ static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
 	else
 		buf->allocator = &pool_allocator;
 
-	addr = buf->allocator->alloc(&args, &page);
+	addr = buf->allocator->alloc(&args, &page, is_coherent);
 
 	if (page) {
 		unsigned long flags;
@@ -1264,7 +1277,8 @@ static inline void __free_iova(struct dma_iommu_mapping *mapping,
 static const int iommu_order_array[] = { 9, 8, 4, 0 };
 
 static struct page **__iommu_alloc_buffer(struct device *dev, size_t size,
-					  gfp_t gfp, struct dma_attrs *attrs)
+					  gfp_t gfp, struct dma_attrs *attrs,
+					  bool is_coherent)
 {
 	struct page **pages;
 	int count = size >> PAGE_SHIFT;
@@ -1288,7 +1302,7 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t size,
 		if (!page)
 			goto error;
 
-		__dma_clear_buffer(page, size);
+		__dma_clear_buffer(page, size, is_coherent);
 
 		for (i = 0; i < count; i++)
 			pages[i] = page + i;
@@ -1338,7 +1352,7 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t size,
 				pages[i + j] = pages[i] + j;
 		}
 
-		__dma_clear_buffer(pages[i], PAGE_SIZE << order);
+		__dma_clear_buffer(pages[i], PAGE_SIZE << order, is_coherent);
 		i += 1 << order;
 		count -= 1 << order;
 	}
@@ -1516,7 +1530,8 @@ static void *arm_iommu_alloc_attrs(struct device *dev, size_t size,
 	 */
 	gfp &= ~(__GFP_COMP);
 
-	pages = __iommu_alloc_buffer(dev, size, gfp, attrs);
+	/* For now always consider we are in a non-coherent case */
+	pages = __iommu_alloc_buffer(dev, size, gfp, attrs, false);
 	if (!pages)
 		return NULL;
 
-- 
2.5.0

Re: [PATCH v6 1/2] ARM: dma-mapping: Don't use outer_flush_range when the L2C is coherent

[Russell King - ARM Linux]

On Thu, Mar 31, 2016 at 11:09:39AM +0200, Gregory CLEMENT wrote:
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index deac58d5f1f7..1538bb293e90 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -61,7 +61,7 @@ struct arm_dma_free_args {
>  
>  struct arm_dma_allocator {
>  	void *(*alloc)(struct arm_dma_alloc_args *args,
> -		       struct page **ret_page);
> +		       struct page **ret_page, bool is_coherent);

This should be named "l2_coherent" because it controls whether L2
cache flushing is done: L1 cache flushing calls are still present.

-- 
RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.

Re: [PATCH v6 1/2] ARM: dma-mapping: Don't use outer_flush_range when the L2C is coherent

[Gregory CLEMENT]

Hi Russell King,
 
 On jeu., avril 07 2016, Russell King - ARM Linux <linux@arm.linux.org.uk> wrote:

> On Thu, Mar 31, 2016 at 11:09:39AM +0200, Gregory CLEMENT wrote:
>> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
>> index deac58d5f1f7..1538bb293e90 100644
>> --- a/arch/arm/mm/dma-mapping.c
>> +++ b/arch/arm/mm/dma-mapping.c
>> @@ -61,7 +61,7 @@ struct arm_dma_free_args {
>>  
>>  struct arm_dma_allocator {
>>  	void *(*alloc)(struct arm_dma_alloc_args *args,
>> -		       struct page **ret_page);
>> +		       struct page **ret_page, bool is_coherent);
>
> This should be named "l2_coherent" because it controls whether L2
> cache flushing is done: L1 cache flushing calls are still present.

I've just sent a new version taking into account your remark.

Thanks,

Gregory

>
> -- 
> RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
> according to speedtest.net.

-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com

Re: [PATCH v6 1/2] ARM: dma-mapping: Don't use outer_flush_range when the L2C is coherent

[Rabin Vincent]

On Thu, Mar 31, 2016 at 11:09:39AM +0200, Gregory CLEMENT wrote:
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index deac58d5f1f7..1538bb293e90 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -61,7 +61,7 @@ struct arm_dma_free_args {
>  
>  struct arm_dma_allocator {
>  	void *(*alloc)(struct arm_dma_alloc_args *args,
> -		       struct page **ret_page);
> +		       struct page **ret_page, bool is_coherent);
>  	void (*free)(struct arm_dma_free_args *args);
>  };

Could you please add this parameter to the arm_dma_alloc_args structure
instead?  As you see from the code, that's where all the other various
parameters needed by the allocators are grouped.

Re: [PATCH v6 1/2] ARM: dma-mapping: Don't use outer_flush_range when the L2C is coherent

[Gregory CLEMENT]

Hi Rabin,
 
 On ven., avril 08 2016, Rabin Vincent <rabin@rab.in> wrote:

> On Thu, Mar 31, 2016 at 11:09:39AM +0200, Gregory CLEMENT wrote:
>> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
>> index deac58d5f1f7..1538bb293e90 100644
>> --- a/arch/arm/mm/dma-mapping.c
>> +++ b/arch/arm/mm/dma-mapping.c
>> @@ -61,7 +61,7 @@ struct arm_dma_free_args {
>>  
>>  struct arm_dma_allocator {
>>  	void *(*alloc)(struct arm_dma_alloc_args *args,
>> -		       struct page **ret_page);
>> +		       struct page **ret_page, bool is_coherent);
>>  	void (*free)(struct arm_dma_free_args *args);
>>  };
>
> Could you please add this parameter to the arm_dma_alloc_args structure
> instead?  As you see from the code, that's where all the other various
> parameters needed by the allocators are grouped.

I will do it inthe 8th version, it indeed simplify a little the patch.

Thanks,

Gregory


-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com