Re: [PATCH 1/1] powerpc: fix missing L2 cache size in /sys/devices/system/cpu

Benjamin Herrenschmidt [off-list ref] wrote:

On Mon, 2015-02-09 at 15:43 -0800, Dave Olson wrote:

quoted

Michael Ellerman [off-list ref] wrote:

quoted

On Mon, 2015-02-09 at 14:14 -0800, Dave Olson wrote:

quoted

From: Dave Olson <redacted>

Fix missing L2 cache size in /sys/devices/system/cpu/cpu0/cache/index2/size
This bug appears to be introduced in 2.6.29 by 93197a36a9c16a85fb24cf5a8639f7bf9af838a3.
The missing entry caused lscpu to error out on e500v2 devices, and probably others
 error: cannot open /sys/devices/system/cpu/cpu0/cache/index2/size: No such file or directory
The DTS files we see use cache-size for the unified L2 cache size, not d-cache-size

Can you convince me that this is not going to break other machines that have
"d-cache-size" but not "cache-size"?

I'm unable to find any dts file that uses d-cache-size for the L2
unified cache.  All in the powerpc tree in arch/powerpc/boot/dts/*
are using cache-size in the L2 description for the cache size.

As best as I can tell from looking around, this is universal.

It may be universal for embedded machines using DTS in the kernel tree
but it's definitely not true of any Mac or server machine (from which
there is no DTS in the kernel as we get the DT from the firmware).

OK, now that I understand that's the case, I'll have to go back and
re-do the patch to handle both cache-size and d-cache-size for the
L2 cache (using whichever is present).

I don't have any power Macs to use for testing, would one of you be
willing and able to verify the patch on a power Mac?

The patch below fixes my problem, and I don't think it will break
platforms like the PowerPC Mac that use d-cache-size
=====

diff --git a/arch/powerpc/kernel/cacheinfo.c b/arch/powerpc/kernel/cacheinfo.c
index a3c684b..0d1f879 100644
--- a/arch/powerpc/kernel/cacheinfo.c
+++ b/arch/powerpc/kernel/cacheinfo.c

@@ -200,6 +200,10 @@ static int cache_size(const struct cache *cache, unsigned int *ret)
 	propname = cache_type_info[cache->type].size_prop;
 
 	cache_size = of_get_property(cache->ofnode, propname, NULL);
+	if (!cache_size && cache->type == CACHE_TYPE_UNIFIED) {
+        /* most embedded systems with L2 use "cache-size", allow that also */
+        cache_size = of_get_property(cache->ofnode, "cache-size", NULL);
+    }
 	if (!cache_size)
 		return -ENODEV;
 

=====

Thanks,

Dave Olson
olson@cumulusnetworks.com