[PATCH] cpm_uart: Allocate DPRAM memory for SMC ports on CPM2-based platforms.

[Scott Wood]

On Tue, Mar 25, 2008 at 04:34:46PM +0100, Laurent Pinchart wrote:
> On Tuesday 25 March 2008 15:58, Scott Wood wrote:
> > Please maintain backward compatibility with older device trees (by
> > checking the length of the second reg resource).  At the very least,
> > update the device trees that are affected.
> 
> I haven't seen any CPM2-based board using SMC ports in the device trees 
> available in arch/powerpc/boot/dts.

ep8248e

> Should I still maintain compatibility with older device trees ? Is there any 
> out-of-tree PQ2 boards using udbg and SMC ?

Yes, I've answered questions on the lists from at least one person using
a custom board with cpm2 smc.

> What about printing a warning if the second reg resource has the wrong
> size ?

The only way you'll see the warning is if udbg is enabled. :-P

Will a CPM reset blow away the portion of muram that holds the SMC pram
pointer?  If not (and I don't think it will), just return the device tree
reg resource as is currently done if the resource is the wrong size.

> > After this point, even if you don't reset the CPM, udbg printk is broken
> > because you moved pram.  The udbg disabling will have to be moved before
> > this.
> 
> Moving the SMC pram doesn't break udbg printk in itself. What will break it is 
> moving the TX BDs, but the end result is the same, moving pram will result in 
> udbg being broken.
> 
> The cpm_uart driver disable udbg before allocating the new BDs. What about 
> moving that right before moving the parameter RAM ? cpm_uart_request_port(), 
> which is called in between, already disables RX and TX on the port, so we 
> won't loose any debug message.

cpm_uart_request_port() returns without doing that if it's a console
port.  I think the current placement of the udbg disable will be fine.

-Scott