Re: [BUG] dma-ranges, reserved memory regions, dma_alloc_coherent: possible bug?

[Vladimir Murzin <vladimir.murzin@arm.com>]

On 10/14/19 4:01 PM, Vladimir Murzin wrote:
> On 10/14/19 2:54 PM, Robin Murphy wrote:
>> On 13/10/2019 15:28, Daniele Alessandrelli wrote:
>>> Hi,
>>>
>>> It looks like dma_alloc_coherent() is setting the dma_handle output
>>> parameter to the memory physical address and not the device bus
>>> address when the device is using reserved memory regions for DMA
>>> allocation. This is despite using 'dma_ranges' in the device tree to
>>> describe the DMA memory mapping. Is this expected behavior or a bug?
>>
>> That does sound like a bug :(
>>
>>> Here is a reduced version of the device tree I'm using:
>>> \ {
>>>          reserved-memory {
>>>                  #address-cells = <2>;
>>>                  #size-cells = <2>;
>>>                  ranges;
>>>                  mydev_rsvd: rsvd_mem@494800000 {
>>>                          compatible = "shared-dma-pool";
>>>                          reg = <0x4 0x94800000 0x0 0x200000>;
>>>                          no-map;
>>>                  };
>>>          };
>>>          soc {
>>>                  compatible = "simple-bus";
>>>                  #address-cells = <2>;
>>>                  #size-cells = <2>;
>>>                  ranges;
>>>                  dma_ranges;
>>>
>>>                  mybus {
>>>                          ranges = <>;
>>>                          dma-ranges = <>;
>>>                          compatible = "simple-bus";
>>>                          #address-cells = <2>;
>>>                          #size-cells = <2>;
>>>                          ranges =     <0x0 0x0  0x0 0x0  0x0 0x80000000>;
>>>                          dma-ranges = <0x0 0x80000000  0x4 0x80000000
>>> 0x0 0x80000000>;
>>>
>>>                          mydevice {
>>>                                  compatible = "my-compatible-string";
>>>                                  memory-region = <&mydev_rsvd>;
>>>                          }
>>>                  }
>>>          }
>>> };
>>>
>>> It looks like this issue was previously fixed by commit c41f9ea998f3
>>> ("drivers: dma-coherent: Account dma_pfn_offset when used with device
>>> tree") which introduced a new function ('dma_get_device_base()') to
>>> return the reserved memory address as seen by the device. However,
>>> such a function, even if still there, is not used anymore in latest
>>> code (as of v5.4-rc2). Was that done for a specific reason? Or is it
>>> just a mistake?
>>
>> Hmm, it looks like 43fc509c3efb ("dma-coherent: introduce interface for default DMA pool") removed the caller of dma_get_device_base() in the alloc path shortly after it was introduced, which certainly appears as if it may have been unintentional - Vladimir?
> 
> I do not remember it was intentional. Looking at history, default DMA pool was a response
> to another report. However, now I'm wondering why it was not caught by STM32 - most of that
> work was required to support "dma-ranges" with NOMMU+caches (Cortex-M7).
> 
> Alex (or anybody else from ST), maybe you have some input?

Seem they do not care :)

I'm wondering if I've missed something with diff bellow (it was a long time ago when I touched DMA)?

diff --git a/arch/arm/mm/dma-mapping-nommu.c b/arch/arm/mm/dma-mapping-nommu.c
index db92478..287ef89 100644
--- a/arch/arm/mm/dma-mapping-nommu.c
+++ b/arch/arm/mm/dma-mapping-nommu.c
@@ -35,7 +35,7 @@ static void *arm_nommu_dma_alloc(struct device *dev, size_t size,
 				 unsigned long attrs)
 
 {
-	void *ret = dma_alloc_from_global_coherent(size, dma_handle);
+	void *ret = dma_alloc_from_global_coherent(dev, size, dma_handle);
 
 	/*
 	 * dma_alloc_from_global_coherent() may fail because:
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 4a1c4fc..10918c5 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -162,7 +162,7 @@ int dma_release_from_dev_coherent(struct device *dev, int order, void *vaddr);
 int dma_mmap_from_dev_coherent(struct device *dev, struct vm_area_struct *vma,
 			    void *cpu_addr, size_t size, int *ret);
 
-void *dma_alloc_from_global_coherent(ssize_t size, dma_addr_t *dma_handle);
+void *dma_alloc_from_global_coherent(struct device *dev, ssize_t size, dma_addr_t *dma_handle);
 int dma_release_from_global_coherent(int order, void *vaddr);
 int dma_mmap_from_global_coherent(struct vm_area_struct *vma, void *cpu_addr,
 				  size_t size, int *ret);
@@ -172,7 +172,7 @@ int dma_mmap_from_global_coherent(struct vm_area_struct *vma, void *cpu_addr,
 #define dma_release_from_dev_coherent(dev, order, vaddr) (0)
 #define dma_mmap_from_dev_coherent(dev, vma, vaddr, order, ret) (0)
 
-static inline void *dma_alloc_from_global_coherent(ssize_t size,
+static inline void *dma_alloc_from_global_coherent(struct device *dev, ssize_t size,
 						   dma_addr_t *dma_handle)
 {
 	return NULL;
diff --git a/kernel/dma/coherent.c b/kernel/dma/coherent.c
index 545e386..551b0eb 100644
--- a/kernel/dma/coherent.c
+++ b/kernel/dma/coherent.c
@@ -123,8 +123,9 @@ int dma_declare_coherent_memory(struct device *dev, phys_addr_t phys_addr,
 	return ret;
 }
 
-static void *__dma_alloc_from_coherent(struct dma_coherent_mem *mem,
-		ssize_t size, dma_addr_t *dma_handle)
+static void *__dma_alloc_from_coherent(struct device *dev,
+				       struct dma_coherent_mem *mem,
+				       ssize_t size, dma_addr_t *dma_handle)
 {
 	int order = get_order(size);
 	unsigned long flags;
@@ -143,7 +144,7 @@ static void *__dma_alloc_from_coherent(struct dma_coherent_mem *mem,
 	/*
 	 * Memory was found in the coherent area.
 	 */
-	*dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
+	*dma_handle = dma_get_device_base(dev, mem) + (pageno << PAGE_SHIFT);
 	ret = mem->virt_base + (pageno << PAGE_SHIFT);
 	spin_unlock_irqrestore(&mem->spinlock, flags);
 	memset(ret, 0, size);
@@ -175,17 +176,18 @@ int dma_alloc_from_dev_coherent(struct device *dev, ssize_t size,
 	if (!mem)
 		return 0;
 
-	*ret = __dma_alloc_from_coherent(mem, size, dma_handle);
+	*ret = __dma_alloc_from_coherent(dev, mem, size, dma_handle);
 	return 1;
 }
 
-void *dma_alloc_from_global_coherent(ssize_t size, dma_addr_t *dma_handle)
+void *dma_alloc_from_global_coherent(struct device *dev, ssize_t size,
+				     dma_addr_t *dma_handle)
 {
 	if (!dma_coherent_default_memory)
 		return NULL;
 
-	return __dma_alloc_from_coherent(dma_coherent_default_memory, size,
-			dma_handle);
+	return __dma_alloc_from_coherent(dev, dma_coherent_default_memory, size,
+					 dma_handle);
 }
 
 static int __dma_release_from_coherent(struct dma_coherent_mem *mem,

> 
> Cheers
> Vladimir
> 
>>
>> Robin.
> 

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