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

On Wed, 2008-01-09 at 20:47 -0600, Linas Vepstas wrote:

On 09/01/2008, Michael Ellerman [off-list ref] wrote:

quoted

quoted

quoted

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