[Skiboot] [PATCH] hdata/cpu: account for p9 shared caches

[Oliver O'Halloran]

On P9 the L2 and L3 caches are shared between pairs of SMT=4 cores.
Currently this is not accounted for when creating caches nodes in
the device tree. This patch adds additional checking so that a
cache node is only created for the first core in the pair and
the second core will reference the cache correctly.

Signed-off-by: Oliver O'Halloran <oohall at gmail.com>
---
 hdata/cpu-common.c | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/hdata/cpu-common.c b/hdata/cpu-common.c
index 50c6adc766c0..112847d5b4c3 100644
--- a/hdata/cpu-common.c
+++ b/hdata/cpu-common.c
@@ -313,24 +313,46 @@ static struct dt_node *l2_cache_node(struct dt_node *cpus,
 	return node;
 }
 
+static struct dt_node *find_l2_node(struct dt_node *cpus, u32 pir)
+{
+	char name[32];
+
+	snprintf(name, sizeof(name), "l2-cache@%.08x", pir);
+	return dt_find_by_name(cpus, name);
+}
+
 uint32_t add_core_cache_info(struct dt_node *cpus,
 			     const struct sppcia_cpu_cache *cache,
-			     uint32_t int_server, int okay)
+			     uint32_t core_pir, int okay)
 {
 	struct dt_node *l2_node, *l3_node, *l35_node;
 	uint32_t unit_addr;
 
+	/*
+	 * On P9 the L2 is shared by pairs of SMT=4 cores. We only
+	 * want to add the cache nodes for the first of these cores
+	 * so we mask the PIR and check for an existing node.
+	 */
+	if (proc_gen == proc_gen_p9) {
+		core_pir &= ~0x7;
+
+		l2_node = find_l2_node(cpus, core_pir);
+		if (l2_node)
+			return l2_node->phandle;
+	}
+
 	/* Use Processor Interrupt Line to genarate cache unit address */
-	unit_addr = 0x20 << 24 | int_server;
+	unit_addr = 0x20 << 24 | core_pir;
 	l2_node = l2_cache_node(cpus, cache, unit_addr, okay);
 
-	unit_addr = 0x30 << 24 | int_server;
+	unit_addr = 0x30 << 24 | core_pir;
 	l3_node = l3_cache_node(cpus, cache, unit_addr, okay);
+
 	/* Represents the next level of cache in the memory hierarchy */
 	dt_add_property_cells(l2_node, "l2-cache", l3_node->phandle);
 
 	if (be32_to_cpu(cache->l35_dcache_size_kb)) {
-		unit_addr = 0x35 << 24 | int_server;
+		unit_addr = 0x35 << 24 | core_pir;
 		l35_node = l35_cache_node(cpus, cache, unit_addr, okay);
 		dt_add_property_cells(l3_node, "l2-cache", l35_node->phandle);
 	}
-- 
2.9.3