linux-kernel - [PATCH v3 2/2] arm64: cacheinfo: add support to override cache levels via device tree

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Date:   Mon, 16 Jan 2017 10:40:44 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Tan Xiaojun <tanxiaojun@...wei.com>,
        Mark Rutland <mark.rutland@....com>
Subject: [PATCH v3 2/2] arm64: cacheinfo: add support to override cache levels via device tree

The cache hierarchy can be identified through Cache Level ID(CLIDR)
architected system register. However in some cases it will provide
only the number of cache levels that are integrated into the processor
itself. In other words, it can't provide any information about the
caches that are external and/or transparent.

Some platforms require to export the information about all such external
caches to the userspace applications via the sysfs interface.

This patch adds support to override the cache levels using device tree
to take such external non-architected caches into account.

Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will.deacon@....com>
Cc: Mark Rutland <mark.rutland@....com>
Tested-by: Tan Xiaojun <tanxiaojun@...wei.com>
Signed-off-by: Sudeep Holla <sudeep.holla@....com>
---
 arch/arm64/kernel/cacheinfo.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/cacheinfo.c b/arch/arm64/kernel/cacheinfo.c
index 9617301f76b5..3f2250fc391b 100644
--- a/arch/arm64/kernel/cacheinfo.c
+++ b/arch/arm64/kernel/cacheinfo.c
@@ -84,7 +84,7 @@ static void ci_leaf_init(struct cacheinfo *this_leaf,

 static int __init_cache_level(unsigned int cpu)
 {
-	unsigned int ctype, level, leaves;
+	unsigned int ctype, level, leaves, of_level;
 	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);

 	for (level = 1, leaves = 0; level <= MAX_CACHE_LEVEL; level++) {
@@ -97,6 +97,17 @@ static int __init_cache_level(unsigned int cpu)
 		leaves += (ctype == CACHE_TYPE_SEPARATE) ? 2 : 1;
 	}

+	of_level = of_find_last_cache_level(cpu);
+	if (level < of_level) {
+		/*
+		 * some external caches not specified in CLIDR_EL1
+		 * the information may be available in the device tree
+		 * only unified external caches are considered here
+		 */
+		leaves += (of_level - level);
+		level = of_level;
+	}
+
 	this_cpu_ci->num_levels = level;
 	this_cpu_ci->num_leaves = leaves;
 	return 0;
--
2.7.4