linux-kernel - [PATCH v4 07/20] cacheinfo: Use cache identifiers to check if the caches are shared if available

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Date:   Tue, 21 Jun 2022 20:20:21 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     linux-kernel@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Atish Patra <atishp@...shpatra.org>,
        Atish Patra <atishp@...osinc.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Qing Wang <wangqing@...o.com>,
        Rob Herring <robh+dt@...nel.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Ionela Voinescu <ionela.voinescu@....com>,
        Pierre Gondois <pierre.gondois@....com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-riscv@...ts.infradead.org
Subject: [PATCH v4 07/20] cacheinfo: Use cache identifiers to check if the caches are shared if available

The cache identifiers is an optional property on most of the platforms. The
presence of one must be indicated by the CACHE_ID valid bit in the attributes.

We can use the cache identifiers provided by the firmware to check if any
two cpus share the same cache instead of relying on the fw_token generated
and set in the OS.

Signed-off-by: Sudeep Holla <sudeep.holla@....com>
---
 drivers/base/cacheinfo.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index 2aa9e8e341b7..167abfa6f37d 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -44,6 +44,10 @@ static inline bool cache_leaves_are_shared(struct cacheinfo *this_leaf,
 	if (!(IS_ENABLED(CONFIG_OF) || IS_ENABLED(CONFIG_ACPI)))
 		return !(this_leaf->level == 1);
 
+	if ((sib_leaf->attributes & CACHE_ID) &&
+	    (this_leaf->attributes & CACHE_ID))
+		return sib_leaf->id == this_leaf->id;
+
 	return sib_leaf->fw_token == this_leaf->fw_token;
 }
 
@@ -56,7 +60,8 @@ bool last_level_cache_is_valid(unsigned int cpu)
 
 	llc = per_cpu_cacheinfo_idx(cpu, cache_leaves(cpu) - 1);
 
-	return !!llc->fw_token;
+	return (llc->attributes & CACHE_ID) || !!llc->fw_token;
+
 }
 
 bool last_level_cache_is_shared(unsigned int cpu_x, unsigned int cpu_y)
-- 
2.36.1