linux-kernel - [PATCH 2/3] cacheinfo: Check cache properties are present in DT

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Date:   Mon, 27 Mar 2023 13:59:50 +0200
From:   Pierre Gondois <pierre.gondois@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Radu Rendec <rrendec@...hat.com>,
        Pierre Gondois <pierre.gondois@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Akihiko Odaki <akihiko.odaki@...nix.com>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Gavin Shan <gshan@...hat.com>,
        Jeremy Linton <jeremy.linton@....com>,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH 2/3] cacheinfo: Check cache properties are present in DT

If a Device Tree (DT) is used, the presence of cache properties is
assumed. Not finding any is not considered. For arm64 platforms,
cache information can be fetched from the clidr_el1 register.
Checking whether cache information is available in the DT
allows to switch to using clidr_el1.

init_of_cache_level()
\-of_count_cache_leaves()
will assume there a 2 cache leaves (L1 data/instruction caches), which
can be different from clidr_el1 information.

cache_setup_of_node() tries to read cache properties in the DT.
If there are none, this is considered a success. Knowing no
information was available would allow to switch to using clidr_el1.

Signed-off-by: Pierre Gondois <pierre.gondois@....com>
---
 drivers/base/cacheinfo.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index 4ca117574af1..5b0edf2d5da8 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -78,6 +78,9 @@ bool last_level_cache_is_shared(unsigned int cpu_x, unsigned int cpu_y)
 }
 
 #ifdef CONFIG_OF
+
+static bool of_check_cache_nodes(struct device_node *np);
+
 /* OF properties to query for a given cache type */
 struct cache_type_info {
 	const char *size_prop;
@@ -205,6 +208,11 @@ static int cache_setup_of_node(unsigned int cpu)
 		return -ENOENT;
 	}
 
+	if (!of_check_cache_nodes(np)) {
+		of_node_put(np);
+		return -ENOENT;
+	}
+
 	prev = np;
 
 	while (index < cache_leaves(cpu)) {
@@ -229,6 +237,25 @@ static int cache_setup_of_node(unsigned int cpu)
 	return 0;
 }
 
+static bool of_check_cache_nodes(struct device_node *np)
+{
+	struct device_node *next;
+
+	if (of_property_read_bool(np, "cache-size")   ||
+	    of_property_read_bool(np, "i-cache-size") ||
+	    of_property_read_bool(np, "d-cache-size") ||
+	    of_property_read_bool(np, "cache-unified"))
+		return true;
+
+	next = of_find_next_cache_node(np);
+	if (next) {
+		of_node_put(next);
+		return true;
+	}
+
+	return false;
+}
+
 static int of_count_cache_leaves(struct device_node *np)
 {
 	unsigned int leaves = 0;
@@ -260,6 +287,9 @@ int init_of_cache_level(unsigned int cpu)
 	struct device_node *prev = NULL;
 	unsigned int levels = 0, leaves, level;
 
+	if (!of_check_cache_nodes(np))
+		goto err_out;
+
 	leaves = of_count_cache_leaves(np);
 	if (leaves > 0)
 		levels = 1;
-- 
2.25.1