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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 do I insert a phram module?

I need to directly write to and read from physical memory for my research and the only way I can think of doing it is with a kernel module. I found this generic device driver called phram that I've been trying to use to map memory and then write to…
smbullet
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Control the ARM Cortex M3/M4 DMA rate to peripherals.

I want to stream data, byte-by-byte, from RAM to a port (GPIO pins) on an ARM Cortex M3 (and possibly M4 in future). Is there a way of controlling the rate, relative to the bus speed? i.e. if I'm running the M3 at 100MHz, can I do DMA at 10MHz, for…
fadedbee
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how to read the value of variable type dma_addr_t

dma_alloc_coherent() returns a pointer for storing any data. And this function takes a variable of type dma_addr_t and it is used for DMA operations. So I want to read this value before DMA operation starts.
Raj
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DMA controller features and terminology

I'm reading some technical reference of a DMA controller but I don't understand many things, it seems that I'm missing some points, I have no practical experience dealing directly with DMA but want to understand at least the theory. In the document…
Bush
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Trigger SPI communication using a timer

I'm trying to trigger a SPI communication using a timer on the NXP LPC1788 microcontroller. In the features of the DMA user manual it's written that the controller can use a timer for triggering a DMA burst. But I can't find a hint where the trigger…
Jonny Schubert
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Is it possible to use dma_set_mask() to tell kernel not to use memory under 4G

My pcie device has a bug that it cant dma to addresses below 4G, What mask should i use with dma_set_mask to tell this to the kernel?
yonigo
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DMA in Linux and CPU-driver interaction

The other day I was reading an article where the author was talking about DMA, and how it helps copy packets across the PCI bus into memory, without the CPU being involved. Then it says: The only overhead is that about once a millisecond, the CPU…
Mark
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What does the X_MODIFY do in the ADSP-BF537's DMA? (Analog Devices)

I've been having a problem trying to figure out what "X_MODIFY" from EZ-Kit Lite BF537 (Analog Devices) means, which is part of the DMA's configuration. What exactly does it change? It's the step take after the loop begins? Here is the code. You…
CristianSR
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Use dma transfert with Cyclone V Avalon-MM for PCIe

Is it possible to do DMA transferts with the IP core «Cyclone V Avalon-MM for PCIe» provided by altera in Qsys (quartus 14.0) ? Altera provide an ip-core named «Cyclone V Avalon-MM DMA for PCIe» to do dma transfert. But this ip-core does not support…
FabienM
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DSPIC33F UART DMA Example not working

I am trying to use DMA for my UART Rx and Tx. Till now I had the freeRTOS version of the serial demo working fine. It still works fine. However, now I have incorporated the UART DMA example, from the example projects. the code is conditionally…
Vishal
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When does PL080 DMAC generate error interupt?

DMAC pl080 DMACIntErrorStatus register with register address 0x00C which is a read only register shows the error on the channel by making that particular bit active. Under what conditions the particular channel bit goes active.
Divyanshu Kapoor
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DMA and the possible movability of kernel mode memory allocations

Of course in general the physical memory behind user mode allocations (e. g. pointers returned by malloc()) might very well move to some different physical address at the discretion of the kernel (for example if the memory is swapped to disk and is…
user1967844
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transfer from dma to disk

I receive packets from dma in streaming mode (32 packets per call), I need to copy them to a file. When all dma buffer is full I use memcpy to take dma buffer to another ram buffer and another thread copy it to the file. But I realised memcpy…
pfdx44
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Is there a way to read a file into memory using DMA in Linux?

Say, I have a huge file which I want to load into memory. Is it possible to use the DMA to quickly load the data from the file into the memory in Linux? If so, how?
MetallicPriest
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UART/DMA interrupt not being triggered on dsPIC33

I have a dsPIC33 with an explorer board 16. The entire code base is fairly lengthy but the problem is isolated to the DMA interrupt. It is not being triggered even though I have pretty much copied the Microchip UARTloopback example. I have read the…
deathlok0000
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