Re: Driver: accessing peripheral on main bus - iowrite32(), memcpy_toio()

[AKS <aung.aungkyawsoe@xxxxxxxxx>]

Portability

On Fri, Aug 8, 2008 at 8:18 AM, Patrick <kpa_info@xxxxxxxx> wrote:
> Hello all,
>
> I am developing a driver for my own board based on an AT91rm9200. An FPGA is
> attached to the ARM with the static memory controller. I need to write a big
> amount (260kbytes) of data inside the fpga. I have some question about the
> way to access the fpga (like a memory) from my driver.
>
> Currently I am using the following function in the following order and it
> works nice:
> - request_mem_region(...)
> - ioremap(...)
> - iowrite32(...) //using the address returned by ioremap
> - wmb()
>
> But I am a little bit confused about using all those function. When I look
> inside the mach independent code I don't see iowrite or wmb but only simple
> pointer accessing the hardware.
>
> What is exactly the goal of iowrite, wmb and memcpy_toio function family in
> comparison with the direct pointer writing?
>
> For writing a block of data (260k) inside my fpga I have tried two different
> way: The first is with a loop with iowrite32() and wmb() the second is with
> memcpy_toio(). Surprisingly the technique with a loop is near two time
> faster than the memcpy_toio() ! Do you know why?
>
> Finally what is (in your opinion) the better/faster way to write all my data
> inside the fpga?
>
> Thanks in advance for any kind of help. At this point any information will
> help me!
>
> Patrick
>
>
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