Accessing the CPM2 on an MPC82xx : CPM_MAP_ADDR or cpm2_immr ?

Accessing the CPM2 on an MPC82xx : CPM_MAP_ADDR or cpm2_immr ?

[Laurent Pinchart]

Hi everybody,

I noticed that the CPM2 module is accessed both through CPM_MAP_ADDR (physical 
address) and cpm2_immr (ioremap()ed address). For instance, the fec_enet 
driver configures the IO ports using (cpm2_map_t*)CPM_MAP_ADDR.

What's the correct way to access the CPM2 module ? Does ioremap() map 
CPM_MAP_ADDR to itself so that both ways are correct ?

Laurent Pinchart

Re: Accessing the CPM2 on an MPC82xx : CPM_MAP_ADDR or cpm2_immr ?

[Vitaly Bordug]

On Thu, 2 Feb 2006 14:58:26 +0100
Laurent Pinchart <laurent.pinchart@tbox.biz> wrote:

> Hi everybody,
> 
> I noticed that the CPM2 module is accessed both through CPM_MAP_ADDR (physical 
> address) and cpm2_immr (ioremap()ed address). For instance, the fec_enet 
> driver configures the IO ports using (cpm2_map_t*)CPM_MAP_ADDR.
> 

Mentioned driver is deprecated. 
> What's the correct way to access the CPM2 module ? Does ioremap() map 
> CPM_MAP_ADDR to itself so that both ways are correct ?
> 

Even direct cpm2_immr usage is not a good thing, but I cannot tell more without knowing your concerns. Can you please describe what you are planning to implement, prolly we can advice how to do that proper way.


> Laurent Pinchart
> _______________________________________________
> Linuxppc-embedded mailing list
> Linuxppc-embedded@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-embedded
> 
> 


-- 
Sincerely, 
Vitaly

Re: Accessing the CPM2 on an MPC82xx : CPM_MAP_ADDR or cpm2_immr ?

[Laurent Pinchart]

> > I noticed that the CPM2 module is accessed both through CPM_MAP_ADDR
> > (physical address) and cpm2_immr (ioremap()ed address). For instance, the
> > fec_enet driver configures the IO ports using (cpm2_map_t*)CPM_MAP_ADDR.
>
> Mentioned driver is deprecated.

It has been replaced by drivers/net/fs_enet, right ? The new driver doesn't 
support the LXT971/LXT971A PHY chipsets yet, so I'm still using the old one.

> > What's the correct way to access the CPM2 module ? Does ioremap() map
> > CPM_MAP_ADDR to itself so that both ways are correct ?
>
> Even direct cpm2_immr usage is not a good thing, but I cannot tell more
> without knowing your concerns. Can you please describe what you are
> planning to implement, prolly we can advice how to do that proper way.

I'm currently just hacking IDMA transfers to make sure the signals we plan to 
use on a custom design work as expected. I will later work on the USB host 
controller driver.

The new fs_enet driver internally maps CPM_MAP_ADDR. Should every driver 
create an internal CPM mapping ? Why was the old fec_enet driver able to 
access the CPM through CPM_MAP_ADDR without ioremap()ing it first ?

Laurent Pinchart

Re: Accessing the CPM2 on an MPC82xx : CPM_MAP_ADDR or cpm2_immr ?

[Dan Malek]

On Feb 2, 2006, at 10:42 AM, Laurent Pinchart wrote:

> The new fs_enet driver internally maps CPM_MAP_ADDR. Should every 
> driver
> create an internal CPM mapping ?

Yes, they should.  All drivers should do the ioremap() and stash the
pointer internally.

> .... Why was the old fec_enet driver able to
> access the CPM through CPM_MAP_ADDR without ioremap()ing it first ?

Because that's a long left over "performance hack" from many
years ago when I first implemented the 8xx software.  The IMMR used
to be mapped to a well known virtual address, the board initialization
did this early, and everyone (ab)used it.  This was way back in the 
2.0/2.1
days when it was acceptable to do such things :-)  Due to the CPM2 now
being used on may different Freescale parts, and mapped in various
ways, the internal mapping should be done by every driver.

Thanks.

	-- Dan