Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Dmitry Osipenko <digetx@gmail.com>
To:     Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Cc:     linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org
Subject: [PATCH v1 2/2] memory: tegra20: Protect debug code with a lock
Date:   Wed, 24 Mar 2021 00:04:46 +0300
Message-Id: <20210323210446.24867-2-digetx@gmail.com>
In-Reply-To: <20210323210446.24867-1-digetx@gmail.com>
References: <20210323210446.24867-1-digetx@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Simultaneous accesses to MC_STAT h/w shouldn't be allowed since one
collection process stomps on another. There is no good reason for
polling stats in parallel in practice, nevertheless let's add a
protection lock, just for consistency.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/memory/tegra/tegra20.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/memory/tegra/tegra20.c b/drivers/memory/tegra/tegra20.c
index 4659c0cea30d..2db68a913b7a 100644
--- a/drivers/memory/tegra/tegra20.c
+++ b/drivers/memory/tegra/tegra20.c
@@ -5,6 +5,7 @@
 
 #include <linux/bitfield.h>
 #include <linux/delay.h>
+#include <linux/mutex.h>
 #include <linux/of_device.h>
 #include <linux/slab.h>
 #include <linux/string.h>
@@ -55,6 +56,8 @@
 /* we store collected statistics as a fixed point values */
 #define MC_FX_FRAC_SCALE			100
 
+static DEFINE_MUTEX(tegra20_mc_stat_lock);
+
 struct tegra20_mc_stat_gather {
 	unsigned int pri_filter;
 	unsigned int pri_event;
@@ -615,8 +618,12 @@ static int tegra20_mc_stats_show(struct seq_file *s, void *unused)
 	if (!stats)
 		return -ENOMEM;
 
+	mutex_lock(&tegra20_mc_stat_lock);
+
 	tegra20_mc_collect_stats(mc, stats);
 
+	mutex_unlock(&tegra20_mc_stat_lock);
+
 	seq_puts(s, "Memory client   Events   Timeout   High priority   Bandwidth ARB   RW change   Successive   Page miss\n");
 	seq_puts(s, "-----------------------------------------------------------------------------------------------------\n");
 
-- 
2.30.2