DMA from Local memory to PCI device - DMA Address
I am working on a driver that uses PCI DMA transfers from processor local memory (slave memory) to the PCI device. The board that is use is MIPS based & the kernel version is linux 2.6.18.8. For some reason, i am not able to achieve this. Instead, if i use __get_free_pages which allocates pages from main memory, the dma transfer happens. Given below are the steps i followed for each case
Case 1 : (using get_free_pages)
a. allocate memory
__get_free_pages() ---> returns virtual address
b. assign the physical address to dma_handle
*dma_handle = __pa(ret)
c. Return the uncach address to the callee
return UNCAC_ADDR(ret);
With the above steps dma happen and the system works as expected.
Now, in the next case, i replace step a with my custom function which allocates memory from the system local memory (slave memory). All other steps are kept as is.
Case 2 :
a. allocate memory from slave memory
custom_allocate_memory () ---> returns physical address of the slave memory
__va( custom_allocate_memory () ) ---> this will convert the physical address to virtual memory. This is done so as to keep the step b & step c of Case 1 as it is.
b. assign the physical address to dma_handle
*dma_handle = __pa(ret)
c. Return the uncached address to the callee
return UNCAC_ADDR(ret);
In Case2, the DMA doesn't work and returns an error which indicates that the address provided to the DMA is wrong? What could be the probable mistake i am doing here? Is there anything else to be considered while replacing the __get_free_pages() with my custom function?
Can someone give me a pointer of how Case 2 can be acheived?
-Joe
Categories
- 9.9K All Categories
- 29 LFX Mentorship
- 82 LFX Mentorship: Linux Kernel
- 463 Linux Foundation Boot Camps
- 266 Cloud Engineer Boot Camp
- 93 Advanced Cloud Engineer Boot Camp
- 43 DevOps Engineer Boot Camp
- 28 Cloud Native Developer Boot Camp
- 1 Express Training Courses
- 1 Express Courses - Discussion Forum
- 1.6K Training Courses
- 18 LFC110 Class Forum
- 3 LFC131 Class Forum
- 19 LFD102 Class Forum
- 131 LFD103 Class Forum
- 9 LFD121 Class Forum
- 60 LFD201 Class Forum
- 1 LFD213 Class Forum - Discontinued
- 128 LFD232 Class Forum
- 23 LFD254 Class Forum
- 544 LFD259 Class Forum
- 100 LFD272 Class Forum
- 1 LFD272-JP クラス フォーラム
- 1 LFS145 Class Forum
- 20 LFS200 Class Forum
- 739 LFS201 Class Forum
- 1 LFS201-JP クラス フォーラム
- 1 LFS203 Class Forum
- 36 LFS207 Class Forum
- 295 LFS211 Class Forum
- 53 LFS216 Class Forum
- 45 LFS241 Class Forum
- 39 LFS242 Class Forum
- 33 LFS243 Class Forum
- 10 LFS244 Class Forum
- 27 LFS250 Class Forum
- 1 LFS250-JP クラス フォーラム
- 131 LFS253 Class Forum
- 963 LFS258 Class Forum
- 10 LFS258-JP クラス フォーラム
- 85 LFS260 Class Forum
- 124 LFS261 Class Forum
- 29 LFS262 Class Forum
- 78 LFS263 Class Forum
- 15 LFS264 Class Forum
- 10 LFS266 Class Forum
- 17 LFS267 Class Forum
- 16 LFS268 Class Forum
- 14 LFS269 Class Forum
- 194 LFS272 Class Forum
- 1 LFS272-JP クラス フォーラム
- 206 LFW211 Class Forum
- 148 LFW212 Class Forum
- 890 Hardware
- 212 Drivers
- 74 I/O Devices
- 44 Monitors
- 115 Multimedia
- 206 Networking
- 99 Printers & Scanners
- 85 Storage
- 747 Linux Distributions
- 88 Debian
- 64 Fedora
- 13 Linux Mint
- 13 Mageia
- 24 openSUSE
- 133 Red Hat Enterprise
- 33 Slackware
- 13 SUSE Enterprise
- 354 Ubuntu
- 468 Linux System Administration
- 38 Cloud Computing
- 67 Command Line/Scripting
- Github systems admin projects
- 93 Linux Security
- 77 Network Management
- 107 System Management
- 48 Web Management
- 61 Mobile Computing
- 22 Android
- 25 Development
- 1.2K New to Linux
- 1.1K Getting Started with Linux
- 525 Off Topic
- 127 Introductions
- 211 Small Talk
- 19 Study Material
- 782 Programming and Development
- 256 Kernel Development
- 492 Software Development
- 919 Software
- 255 Applications
- 181 Command Line
- 2 Compiling/Installing
- 76 Games
- 316 Installation
- 46 All In Program
- 46 All In Forum
Upcoming Training
-
August 20, 2018
Kubernetes Administration (LFS458)
-
August 20, 2018
Linux System Administration (LFS301)
-
August 27, 2018
Open Source Virtualization (LFS462)
-
August 27, 2018
Linux Kernel Debugging and Security (LFD440)