Custom PCIe Device Driver

Custom PCIe Device Driver

[Sanka Piyaratna]

Hi Everyone,

I am currently developing a custom PCIe device and the Linux kernel 
driver for this. I am able to use the device as a character device with 
PIO and now I am working on getting the DMA to work. I have implemented 
2 BARs (BAR0 - mem and BAR5 - mem) in the PCIe device. I have 
implemented the DMA in my custom device firmware to transfer a block of 
memory via the PCIe bus and now trying to get this to work with the 
device driver.

As I understand it, I can get hold of the PCI bus to become the bus 
master and then initiate the DMA transfer from my device. However, I 
don't understand how I can specify within my kernel driver how to 
specify which BAR to use.

Does this mean when I initiate a transfer from the hardware, the memory 
get transferred into the location allocated by by  pci_map_single() 
function regardless of which BAR the memory comes from? or do I need to 
specify the BAR using a mask?

Would some one be able to point me to an example code please?

Thanks and Regards,

Sanka

Re: Custom PCIe Device Driver

[Robert Hancock]

Sanka Piyaratna wrote:
> Hi Everyone,
> 
> I am currently developing a custom PCIe device and the Linux kernel 
> driver for this. I am able to use the device as a character device with 
> PIO and now I am working on getting the DMA to work. I have implemented 
> 2 BARs (BAR0 - mem and BAR5 - mem) in the PCIe device. I have 
> implemented the DMA in my custom device firmware to transfer a block of 
> memory via the PCIe bus and now trying to get this to work with the 
> device driver.
> 
> As I understand it, I can get hold of the PCI bus to become the bus 
> master and then initiate the DMA transfer from my device. However, I 
> don't understand how I can specify within my kernel driver how to 
> specify which BAR to use.
> 
> Does this mean when I initiate a transfer from the hardware, the memory 
> get transferred into the location allocated by by  pci_map_single() 
> function regardless of which BAR the memory comes from? or do I need to 
> specify the BAR using a mask?
> 
> Would some one be able to point me to an example code please?
> 
> Thanks and Regards,
> 
> Sanka

Your question doesn't seem to make much sense. DMA transfers have 
nothing to do with BARs at all, they don't come "from" or "to" one.

-- 
Robert Hancock      Saskatoon, SK, Canada
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