LPC bus access howto

LPC bus access howto

[Andre Haupt]

Hi all,

We have a FPGA which will be connected to the LPC bus. This FPGA will
provide some GPIO functionality, a rotary encoder, etc.

Now i want to write a kernel driver to talk to this FPGA.
I am unsure how to get access to the LPC bus in the first place.
What kernel APIs should i use? How to get the memory mapping right, etc?

I would appreciate any pointers to documentation or examples.


cheers,

Andre

LPC bus access howto

[Guillaume Knispel]

On Mon, 21 Nov 2011 17:01:29 +0100
Andre Haupt <andre@bitwigglers.org> wrote:

> Hi all,
> 
> We have a FPGA which will be connected to the LPC bus. This FPGA will
> provide some GPIO functionality, a rotary encoder, etc.
> 
> Now i want to write a kernel driver to talk to this FPGA.
> I am unsure how to get access to the LPC bus in the first place.
> What kernel APIs should i use? How to get the memory mapping right, etc?

The LPC is typically automatically mapped by the hardware (southbridge)
for some fixed ranges, various configurable ranges and might also use
PCI substractive decoding. 

LPC is indeed an ISA bus with the physical layer replaced by something
with fewer signals, but from the point of view of the software there is
almost no difference, so look for how to program ISA drivers and you
will probably have your answer.

-- 
Guillaume Knispel
Avencall - 10 bis, rue Lucien Voilin - 92800 Puteaux
Tel. : (+33) 141 389 960

LPC bus access howto

[Andre Haupt]

On Mon, Nov 21, 2011 at 05:53:30PM +0100, Guillaume Knispel wrote:
> On Mon, 21 Nov 2011 17:01:29 +0100
> Andre Haupt <andre@bitwigglers.org> wrote:
> 
> > Hi all,
> > 
> > We have a FPGA which will be connected to the LPC bus. This FPGA will
> > provide some GPIO functionality, a rotary encoder, etc.
> > 
> > Now i want to write a kernel driver to talk to this FPGA.
> > I am unsure how to get access to the LPC bus in the first place.
> > What kernel APIs should i use? How to get the memory mapping right, etc?
> 
> The LPC is typically automatically mapped by the hardware (southbridge)
> for some fixed ranges, various configurable ranges and might also use
> PCI substractive decoding. 
> 
> LPC is indeed an ISA bus with the physical layer replaced by something
> with fewer signals, but from the point of view of the software there is
> almost no difference, so look for how to program ISA drivers and you
> will probably have your answer.

So request_mem_region(), ioremap(), ioread*() and iowrite*() are my
friends here right?

Still unsure how to obtain the LPC base address. Is this mapped to
0xA0000-0xFFFFF as with ISA?

cheers,

Andre