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Mapping of dmam_alloc_coherent allocated memory to the user space via remap_pfn_range gives pointer to wrong...
I prepare an application running on ARM Intel Cyclone V SoC.
I need to map the DMA coherent memory buffer to the user space.
The buffer is allocated in the device driver with with:
buf_addr = dmam_alloc_coherent(&pdev->dev, size, &dma_addr, GFP_KERNEL);
The mapping is done correctly, and I have verified, that the buffer accessed by the hardware via dma_addr HW address is visible for the kernel via buf_addr pointer.
Then in the mmap function of the device driver I do:
unsigned long physical = virt_to_phys(buf_addr);
unsigned long vsize = vma->vm_end - vma->vm_start;
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
remap_pfn_range(vma,vma->vm_start, physical >> PAGE_SHIFT , vsize, vma->vm_page_prot);
The application mmaps the buffer with:
buf = mmap(NULL,buf_size,PROT_READ | PROT_WRITE, dev_file, MAP_SHARED);
I do not get any error from remap_pfn_range function. Also the application is able to access the mmapped memory, but it is not the buffer allocated with dmam_alloc_coherent.
linux arm mapping dma
asked Jan 1 at 11:45
wzabwzab
290313
add a comment |
I prepare an application running on ARM Intel Cyclone V SoC.
I need to map the DMA coherent memory buffer to the user space.
The buffer is allocated in the device driver with with:
buf_addr = dmam_alloc_coherent(&pdev->dev, size, &dma_addr, GFP_KERNEL);
The mapping is done correctly, and I have verified, that the buffer accessed by the hardware via dma_addr HW address is visible for the kernel via buf_addr pointer.
Then in the mmap function of the device driver I do:
unsigned long physical = virt_to_phys(buf_addr);
unsigned long vsize = vma->vm_end - vma->vm_start;
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
remap_pfn_range(vma,vma->vm_start, physical >> PAGE_SHIFT , vsize, vma->vm_page_prot);
The application mmaps the buffer with:
buf = mmap(NULL,buf_size,PROT_READ | PROT_WRITE, dev_file, MAP_SHARED);
I do not get any error from remap_pfn_range function. Also the application is able to access the mmapped memory, but it is not the buffer allocated with dmam_alloc_coherent.
linux arm mapping dma
asked Jan 1 at 11:45
wzabwzab
290313
add a comment |
I prepare an application running on ARM Intel Cyclone V SoC.
I need to map the DMA coherent memory buffer to the user space.
The buffer is allocated in the device driver with with:
buf_addr = dmam_alloc_coherent(&pdev->dev, size, &dma_addr, GFP_KERNEL);
The mapping is done correctly, and I have verified, that the buffer accessed by the hardware via dma_addr HW address is visible for the kernel via buf_addr pointer.
Then in the mmap function of the device driver I do:
unsigned long physical = virt_to_phys(buf_addr);
unsigned long vsize = vma->vm_end - vma->vm_start;
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
remap_pfn_range(vma,vma->vm_start, physical >> PAGE_SHIFT , vsize, vma->vm_page_prot);
The application mmaps the buffer with:
buf = mmap(NULL,buf_size,PROT_READ | PROT_WRITE, dev_file, MAP_SHARED);
I do not get any error from remap_pfn_range function. Also the application is able to access the mmapped memory, but it is not the buffer allocated with dmam_alloc_coherent.
linux arm mapping dma
asked Jan 1 at 11:45
wzabwzab
290313
I prepare an application running on ARM Intel Cyclone V SoC.
I need to map the DMA coherent memory buffer to the user space.
The buffer is allocated in the device driver with with:
buf_addr = dmam_alloc_coherent(&pdev->dev, size, &dma_addr, GFP_KERNEL);
The mapping is done correctly, and I have verified, that the buffer accessed by the hardware via dma_addr HW address is visible for the kernel via buf_addr pointer.
Then in the mmap function of the device driver I do:
unsigned long physical = virt_to_phys(buf_addr);
unsigned long vsize = vma->vm_end - vma->vm_start;
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
remap_pfn_range(vma,vma->vm_start, physical >> PAGE_SHIFT , vsize, vma->vm_page_prot);
The application mmaps the buffer with:
buf = mmap(NULL,buf_size,PROT_READ | PROT_WRITE, dev_file, MAP_SHARED);
I do not get any error from remap_pfn_range function. Also the application is able to access the mmapped memory, but it is not the buffer allocated with dmam_alloc_coherent.
linux arm mapping dma
linux arm mapping dma
asked Jan 1 at 11:45
wzabwzab
290313
asked Jan 1 at 11:45
wzabwzab
290313
edited Jan 1 at 12:22
wzab
asked Jan 1 at 11:45
wzabwzab
290313
asked Jan 1 at 11:45
wzabwzab
290313
asked Jan 1 at 11:45
wzabwzab
290313
290313
add a comment |
add a comment |
1 Answer
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I have found the macro dma_mmap_coherent that seems to be dedicated particularly for that purpose.
I have verified that the following modification in the mmap function ensures proper operation:
unsigned long vsize = vma->vm_end - vma->vm_start;
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
remap=dma_mmap_coherent(&my_pdev->dev,vma,fdata, dma_addr, vsize);
Because the pdev pointer is not directly delivered to the mmap function it is passed from the probe function via the global variable my_pdev. In case of driver supporting multiple devices, it should be stored in the device context.
answered Jan 1 at 12:20
wzabwzab
290313
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
I have found the macro dma_mmap_coherent that seems to be dedicated particularly for that purpose.
I have verified that the following modification in the mmap function ensures proper operation:
unsigned long vsize = vma->vm_end - vma->vm_start;
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
remap=dma_mmap_coherent(&my_pdev->dev,vma,fdata, dma_addr, vsize);
Because the pdev pointer is not directly delivered to the mmap function it is passed from the probe function via the global variable my_pdev. In case of driver supporting multiple devices, it should be stored in the device context.
answered Jan 1 at 12:20
wzabwzab
290313
add a comment |
I have found the macro dma_mmap_coherent that seems to be dedicated particularly for that purpose.
I have verified that the following modification in the mmap function ensures proper operation:
unsigned long vsize = vma->vm_end - vma->vm_start;
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
remap=dma_mmap_coherent(&my_pdev->dev,vma,fdata, dma_addr, vsize);
Because the pdev pointer is not directly delivered to the mmap function it is passed from the probe function via the global variable my_pdev. In case of driver supporting multiple devices, it should be stored in the device context.
answered Jan 1 at 12:20
wzabwzab
290313
add a comment |
I have found the macro dma_mmap_coherent that seems to be dedicated particularly for that purpose.
I have verified that the following modification in the mmap function ensures proper operation:
unsigned long vsize = vma->vm_end - vma->vm_start;
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
remap=dma_mmap_coherent(&my_pdev->dev,vma,fdata, dma_addr, vsize);
Because the pdev pointer is not directly delivered to the mmap function it is passed from the probe function via the global variable my_pdev. In case of driver supporting multiple devices, it should be stored in the device context.
answered Jan 1 at 12:20
wzabwzab
290313
I have found the macro dma_mmap_coherent that seems to be dedicated particularly for that purpose.
I have verified that the following modification in the mmap function ensures proper operation:
unsigned long vsize = vma->vm_end - vma->vm_start;
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
remap=dma_mmap_coherent(&my_pdev->dev,vma,fdata, dma_addr, vsize);
Because the pdev pointer is not directly delivered to the mmap function it is passed from the probe function via the global variable my_pdev. In case of driver supporting multiple devices, it should be stored in the device context.
answered Jan 1 at 12:20
wzabwzab
290313
answered Jan 1 at 12:20
wzabwzab
290313
answered Jan 1 at 12:20
wzabwzab
290313
answered Jan 1 at 12:20
wzabwzab
290313
290313
add a comment |
add a comment |
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