[PATCH v2 05/15] watchdog: orion: Make RSTOUT register a separate resource

Jason, Arnd:

On Wed, Jan 22, 2014 at 10:48:37AM +0100, Arnd Bergmann wrote:

On Tuesday 21 January 2014 16:33:21 Jason Gunthorpe wrote:

quoted

On Tue, Jan 21, 2014 at 06:12:31AM -0300, Ezequiel Garcia wrote:

quoted

In order to support other SoC, it's required to distinguish
the 'control' timer register, from the 'rstout' register
that enables system reset on watchdog expiration.

quoted

+     res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+     if (!res)
+             return -ENODEV;

           ^^^^^^^^^^^^^^^^^^^^^^

This change seems to break compatibility with existing DT files that
have only a single entry in reg?

Can the value be defaulted some how if missing?

I think this is a direct consequence of the attempt to remove the
header file dependency, since the RSTOUTn_MASK macro is defined
in mach/bridge-regs.h.

Exactly. Just for the record, I warned about this a while back:

http://www.spinics.net/lists/arm-kernel/msg270163.html

That said, it truly sucks to break compatibility so finding a way to
keep backwards compatibility would be certainly desirable.

I don't see a good way out that would preserve backwards compatibility,
other than hardcoding the physical address in the driver, which seems
just as bad as breaking compatibility. That said, it is always the
same constant (0xf1000000 + 0x20000 + 0x0108) on Dove, Kirkwood and
Orion5x (not on mv78xx0, but that doesn't use the wdt), so hardcoding
a fallback would technically work, but we should print a fat warning at
boot time if we actually fall back to that.

Yes, I was thinking just about this. Namely:

If the second resource is missing *and* the compatible-string is
"orion-watchdog" (or it's not DT-registered), then use a hardcoded
RSTOUTn_MASK address. And pr_warn() something.

Thanks for the feedback,
-- 
Ezequiel Garc?a, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com