Subject: Re: [PATCH 1/8] pseries: phyp dump: Docmentation

From: Michael Ellerman <[email-masked]>
Date: Thu, 10 Jan 2008 14:55:50 +1100

On Wed, 2008-01-09 at 20:47 -0600, Linas Vepstas wrote:
> On 09/01/2008, Michael Ellerman <[email-masked]> wrote:
> >
> > > > Only if you can get at rtas, but you can't get at rtas at that point.
> >
> > AFAICT you don't need to get at RTAS, you just need to look at the
> > device tree to see if the property is present, and that is trivial.
> >
> > You probably just need to add a check in early_init_dt_scan_rtas() which
> > sets a flag for the PHYP dump stuff, or add your own scan routine if you
> > need.
> 
> I no longer remember the details. I do remember spending a lot of time
> trying to figure out how to do this. I know I didn't want to write my own scan
> routine; maybe that's what stopped me.  As it happens, we also did most
> of the development on a broken phyp which simply did not even have
> this property, no matter what, and so that may have brain-damaged me.

Sure, the API docs for the kernel are a little lacking ;)

> I went for the "most elegant" solution, where "most elegant" is defined
> as "fewest lines of code", "least effort", etc.
> 
> Manish may need some hands-on help to extract this token during
> early boot.  Hopefully, he'll let us know.

It would just be something like:

--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -901,6 +901,11 @@ int __init early_init_dt_scan_rtas(unsigned long node,
                rtas.size = *sizep;
        }
 
+#ifdef CONFIG_PHYP_DUMP
+       if (of_get_flat_dt_prop(node, "ibm,dump-kernel", NULL))
+               phyp_dump_is_active++;
+#endif
+
 #ifdef CONFIG_UDBG_RTAS_CONSOLE
        basep = of_get_flat_dt_prop(node, "put-term-char", NULL);
        if (basep)

Or to do your own scan routine:

diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index acc0d24..442134e 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -1022,6 +1022,7 @@ void __init early_init_devtree(void *params)
        /* Some machines might need RTAS info for debugging, grab it now. */
        of_scan_flat_dt(early_init_dt_scan_rtas, NULL);
 #endif
+       of_scan_flat_dt(early_init_dt_scan_phyp_dump, NULL);
 
        /* Retrieve various informations from the /chosen node of the
         * device-tree, including the platform type, initrd location and
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 52e95c2..af2b6e8 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -883,6 +883,19 @@ void __init rtas_initialize(void)
 #endif
 }
 
+int __init early_init_dt_scan_phyp_dump(unsigned long node,
+               const char *uname, int depth, void *data)
+{
+#ifdef CONFIG_PHYP_DUMP
+       if (depth != 1 || strcmp(uname, "rtas") != 0)
+               return 0;
+
+       if (of_get_flat_dt_prop(node, "ibm,dump-kernel", NULL))
+               phyp_dump_is_active++;
+#endif
+       return 1;
+}
+
 int __init early_init_dt_scan_rtas(unsigned long node,
                const char *uname, int depth, void *data)
 {

cheers

-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person