[PATCH v1 0/2] Two small dma-coherent bug fixes

[PATCH v1 0/2] Two small dma-coherent bug fixes

[Mark Craske]

This patchset contains the following commits:

Bastian Hecht (1):
  drivers: dma-coherent: Move spinlock in dma_alloc_from_coherent()

George G. Davis (1):
  drivers: dma-coherent: Fix DMA coherent size for less than page

 drivers/base/dma-coherent.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

Background information
----------------------
These 2 commits were originally developed and validated on an ARM i.MX6 based
commercial project running a highly modified 3.14 Linux kernel.
The commits were needed to amend dma_mmap_from_coherent() to deal correctly
with mappings of less than one page, and to improve latency on SMP systems
where large DMA buffers are used.

The commits have been forward-ported to driver-core-next master branch HEAD
(c693593 Linux 4.8-rc5)

Commit details
--------------
This patchset fixes a couple of problems with dma-coherent seen
on a commercial i.MX6 based system.

Note: Testing has only been done on an ARM i.MX6 based platform.
-- 
1.7.9.5

[PATCH v1 1/2] drivers: dma-coherent: Fix DMA coherent size for less than page

[Mark Craske]

From: "George G. Davis" <george_davis@mentor.com>

We fix a bug in dma_mmap_from_coherent() that appears when we map non page
aligned DMA memory. It cuts off the non aligned part (this is different to
dma_alloc_coherent() that always rounds up to full pages). So for mappings
of less than a page we get -ENXIO as dma_mmap_from_coherent() assumes we
want to map zero pages.

Signed-off-by: George G. Davis <george_davis@mentor.com>
Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Mark Craske <Mark_Craske@mentor.com>
---
 drivers/base/dma-coherent.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
index bdf28f7..abd83b7 100644
--- a/drivers/base/dma-coherent.c
+++ b/drivers/base/dma-coherent.c
@@ -262,7 +262,7 @@ int dma_mmap_from_coherent(struct device *dev, struct vm_area_struct *vma,
 		unsigned long off = vma->vm_pgoff;
 		int start = (vaddr - mem->virt_base) >> PAGE_SHIFT;
 		int user_count = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
-		int count = size >> PAGE_SHIFT;
+		int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
 
 		*ret = -ENXIO;
 		if (off < count && user_count <= count - off) {
-- 
1.7.9.5

[PATCH v1 2/2] drivers: dma-coherent: Move spinlock in dma_alloc_from_coherent()

[Mark Craske]

From: Bastian Hecht <bhecht@de.adit-jv.com>

We don't need to hold the spinlock while zeroing the allocated memory.
In case we handle big buffers this is a severe issue as other CPUs might
be spinning half a second or longer.

Signed-off-by: Bastian Hecht <bhecht@de.adit-jv.com>
Signed-off-by: George G. Davis <george_davis@mentor.com>
Signed-off-by: Mark Craske <Mark_Craske@mentor.com>
---
 drivers/base/dma-coherent.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
index abd83b7..d092df4 100644
--- a/drivers/base/dma-coherent.c
+++ b/drivers/base/dma-coherent.c
@@ -165,6 +165,7 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t size,
 	int order = get_order(size);
 	unsigned long flags;
 	int pageno;
+	int dma_memory_map;
 
 	if (!dev)
 		return 0;
@@ -187,11 +188,12 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t size,
 	 */
 	*dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
 	*ret = mem->virt_base + (pageno << PAGE_SHIFT);
-	if (mem->flags & DMA_MEMORY_MAP)
+	dma_memory_map = (mem->flags & DMA_MEMORY_MAP);
+	spin_unlock_irqrestore(&mem->spinlock, flags);
+	if (dma_memory_map)
 		memset(*ret, 0, size);
 	else
 		memset_io(*ret, 0, size);
-	spin_unlock_irqrestore(&mem->spinlock, flags);
 
 	return 1;
 
-- 
1.7.9.5

Re: [PATCH v1 1/2] drivers: dma-coherent: Fix DMA coherent size for less than page

[Greg Kroah-Hartman]

On Thu, Sep 15, 2016 at 10:39:58AM +0100, Mark Craske wrote:
> From: "George G. Davis" <george_davis@mentor.com>
> 
> We fix a bug in dma_mmap_from_coherent() that appears when we map non page
> aligned DMA memory. It cuts off the non aligned part (this is different to
> dma_alloc_coherent() that always rounds up to full pages). So for mappings
> of less than a page we get -ENXIO as dma_mmap_from_coherent() assumes we
> want to map zero pages.
> 
> Signed-off-by: George G. Davis <george_davis@mentor.com>
> Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
> Signed-off-by: Mark Craske <Mark_Craske@mentor.com>
> ---
>  drivers/base/dma-coherent.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
> index bdf28f7..abd83b7 100644
> --- a/drivers/base/dma-coherent.c
> +++ b/drivers/base/dma-coherent.c
> @@ -262,7 +262,7 @@ int dma_mmap_from_coherent(struct device *dev, struct vm_area_struct *vma,
>  		unsigned long off = vma->vm_pgoff;
>  		int start = (vaddr - mem->virt_base) >> PAGE_SHIFT;
>  		int user_count = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
> -		int count = size >> PAGE_SHIFT;
> +		int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
>  
>  		*ret = -ENXIO;
>  		if (off < count && user_count <= count - off) {
> -- 
> 1.7.9.5
> 

Doesn't apply to my tree (or linux-next) :(

Can you refresh this series and resend?

thanks,

greg k-h

[PATCH v2 0/2] Two small dma-coherent bug fixes

[Mark Craske]

This patchset contains the following commits:

Bastian Hecht (1):
  drivers: dma-coherent: Move spinlock in dma_alloc_from_coherent()

George G. Davis (1):
  drivers: dma-coherent: Fix DMA coherent size for less than page

 drivers/base/dma-coherent.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

Background information
----------------------
These 2 commits were originally developed and validated on an ARM i.MX6 based
commercial project running a highly modified 3.14 Linux kernel.
The commits were needed to amend dma_mmap_from_coherent() to deal correctly
with mappings of less than one page, and to improve latency on SMP systems
where large DMA buffers are used.

The commits have been forward-ported to driver-core repo driver-core-next
branch HEAD (6ee6d1c carl9170: fix debugfs crashes)

Commit details
--------------
This patchset fixes a couple of problems with dma-coherent seen
on a commercial i.MX6 based system.

Note: Testing has only been done on an ARM i.MX6 based platform.
-- 
1.7.9.5

[PATCH v2 1/2] drivers: dma-coherent: Fix DMA coherent size for less than page

[Mark Craske]

From: "George G. Davis" <george_davis@mentor.com>

We fix a bug in dma_mmap_from_coherent() that appears when we map non page
aligned DMA memory. It cuts off the non aligned part (this is different to
dma_alloc_coherent() that always rounds up to full pages). So for mappings
of less than a page we get -ENXIO as dma_mmap_from_coherent() assumes we
want to map zero pages.

Signed-off-by: George G. Davis <george_davis@mentor.com>
Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Mark Craske <Mark_Craske@mentor.com>
---
 drivers/base/dma-coherent.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
index db122a0..2789f7a 100644
--- a/drivers/base/dma-coherent.c
+++ b/drivers/base/dma-coherent.c
@@ -262,7 +262,7 @@ int dma_mmap_from_coherent(struct device *dev, struct vm_area_struct *vma,
 		unsigned long off = vma->vm_pgoff;
 		int start = (vaddr - mem->virt_base) >> PAGE_SHIFT;
 		int user_count = vma_pages(vma);
-		int count = size >> PAGE_SHIFT;
+		int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
 
 		*ret = -ENXIO;
 		if (off < count && user_count <= count - off) {
-- 
1.7.9.5

[PATCH v2 2/2] drivers: dma-coherent: Move spinlock in dma_alloc_from_coherent()

[Mark Craske]

From: Bastian Hecht <bhecht@de.adit-jv.com>

We don't need to hold the spinlock while zeroing the allocated memory.
In case we handle big buffers this is a severe issue as other CPUs might
be spinning half a second or longer.

Signed-off-by: Bastian Hecht <bhecht@de.adit-jv.com>
Signed-off-by: George G. Davis <george_davis@mentor.com>
Signed-off-by: Mark Craske <Mark_Craske@mentor.com>
---
 drivers/base/dma-coherent.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
index 2789f7a..640a7e6 100644
--- a/drivers/base/dma-coherent.c
+++ b/drivers/base/dma-coherent.c
@@ -165,6 +165,7 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t size,
 	int order = get_order(size);
 	unsigned long flags;
 	int pageno;
+	int dma_memory_map;
 
 	if (!dev)
 		return 0;
@@ -187,11 +188,12 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t size,
 	 */
 	*dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
 	*ret = mem->virt_base + (pageno << PAGE_SHIFT);
-	if (mem->flags & DMA_MEMORY_MAP)
+	dma_memory_map = (mem->flags & DMA_MEMORY_MAP);
+	spin_unlock_irqrestore(&mem->spinlock, flags);
+	if (dma_memory_map)
 		memset(*ret, 0, size);
 	else
 		memset_io(*ret, 0, size);
-	spin_unlock_irqrestore(&mem->spinlock, flags);
 
 	return 1;
 
-- 
1.7.9.5