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Questions tagged [dma]

Direct memory access (DMA) is a feature of modern computers and microprocessors that allows certain hardware subsystems within the computer to access system memory for reading and/or writing independently of the central processing unit.

Direct memory access (DMA) is a feature of modern computers and microprocessors that allows certain hardware subsystems within the computer to access system memory for reading and/or writing independently of the central processing unit.

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how to convert ELF to DMA format in ARM?

I need to transfer an ELF image in ARM to a DMA format. All I currently have is old code doing this for power PC, but the elf structure seems to be different. Can anyone point me in the direction? OR does anyone know of an open source tool for…
WeaselFox
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C application for parallel communication with direct memory access

I'm having a problem with a parallel connection I've got to establish using DMA (Direct Acces Memory). I've got to write some characters to a parallel port with a given address, through a C application. I know that for a PIO access, there are the…
watiss
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DMA engine is not responding correctly on PowerPC linux

DMA engine is not responding correctly on PowerPC linux. When my PCIe device sends a read / write request to host, timeout happens. I have 1GB of RAM at lower address range. I have called the following…
user2651022
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Should I read file in separate thread in this case?

I am writing an application for embedded linux where 5% of processor time is going in reading a file and 95% on processing it. Can I get some performance improvement if I read file in one thread and keeps on processing in another thread? I am…
SunnyShah
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DMA interrupt for SPI

I'm trying to recreate a project of writing to an SD card (using FatFS) for a dsPIC33FJ128GP802 microcontroller. Currently to collect the date from the SPI I have a do/while that loops 512 times and writes a dummy value to the SPI buffer, wait for…
ritchie888
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What's is the maximal size of single Memwr TLP(BAR ACCESS) from the root complex to endpoint on a X86 platform?

What's is the maximal size of single Memwr TLP(BAR ACCESS) from the root complex to endpoint on a X86 platform? The setup of my system is that there is a PCIe endpoint device plugged into an X86 PC, and the bar0 size of this device is 1 MBytes, and …
TiisCool
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PCIe read write within ISR

I'm modifying a linux PCIe driver to work with altera FPGA PCIe core. Inside my driver code, I'do pci_set_master(dev) to make the PCIe read write working. I'm using altera SG-DMA to do PCIe transfer instead of using ARM DMA. I need to write enable…
Shahril
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Read from another CPU's memory without "asking" for it, (DMA)

I was thinking a bit about DMA. Is it possible to read from a CPU's memory without having the CPU deliver it via some form of communication? Like "reversed DMA". The project for which I'm asking is a quadcopter control board, where I would like to…
user2372772
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How to allocate DMA Buffer of 500 MB in Windows XP

There is a PCI card connected to the PC and we have a GUI for the same. We want to allocate DMA Buffer of about 400 to 600 MB physical memory in RAM in order to read/write from PCI Card (FPGA does Read/Write operation in PCI Card). We are using…
Venu
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I wanted to know more about dma_map and dma_unmap

can somebody point me out to a simple doc on why dma_unmap is required. Please, be free to explain even the dma_map. I new to device drivers. Thanks
Invictus
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LINUX -- DMA for data transfer -- read from SPI --- tx to usart - RPi

How DMA actually works is theory which i knows ;-- http://en.wikipedia.org/wiki/Direct_memory_access But in programming how we have to manage it ? I am using RPI & looking forward to implement following operation using DMA. Suppose if i want to…
user1870619
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get_user_pages -EFAULT error caused by VM_GROWSDOWN flag not set

I'm continue my work on the FGPA driver. Now I'm adding OpenCL support. So I have a following test. It's just add NUM_OF_EXEC times write and read requests of same buffers and after that waits for completion. Each write/read request serialized in…
soh
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How do the writing to an HW controller register and DMA work on ARM arch machines?

while calling this function: static inline void writel(unsigned int v, volatile void __iomem *addr) { *(volatile unsigned int __force *)addr = cpu_to_le32(v); } Does the address is absoulute or pass through the MMU? DMA - does writing to…
0x90
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PCI/PCIe card with DMA capability for device driver training

I trying to learn DMA for device drivers with PCI/PCIe devices, and my platform is linux/bsd. I have found quite a few simple PCI boards for training (such as simple digital I/O boards), but none have hardware complex enough to handle DMA. Is…
Dr. Watson
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Why are most machines not able to address individual bits?

I was reading about bit array and this question came up in my mind. Why are most machines not able to address individual bits? Is it because of the DMA and because it would be too (memory/circuits) expensive to keep an address for each bit?
Luigi Massa Gallerano
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