linux-kernel - [PATCH v1 2/4] memory: tegra: Fix integer overflow on tick value calculation

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Message-Id: <20190411221250.23233-3-digetx@gmail.com>
Date:   Fri, 12 Apr 2019 01:12:48 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>
Cc:     linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1 2/4] memory: tegra: Fix integer overflow on tick value calculation

Multiplying the Memory Controller clock rate by the tick count results
in an integer overflow and in result the truncated tick value is being
programmed into hardware, such that the GR3D memory client performance is
reduced by two times.

Cc: stable <stable@...r.kernel.org>
Signed-off-by: Dmitry Osipenko <digetx@...il.com>
---
 drivers/memory/tegra/mc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/memory/tegra/mc.c b/drivers/memory/tegra/mc.c
index 60474597180b..89e463952b8a 100644
--- a/drivers/memory/tegra/mc.c
+++ b/drivers/memory/tegra/mc.c
@@ -285,7 +285,7 @@ static int tegra_mc_setup_latency_allowance(struct tegra_mc *mc)
 	u32 value;
 
 	/* compute the number of MC clock cycles per tick */
-	tick = mc->tick * clk_get_rate(mc->clk);
+	tick = (unsigned long long)mc->tick * clk_get_rate(mc->clk);
 	do_div(tick, NSEC_PER_SEC);
 
 	value = readl(mc->regs + MC_EMEM_ARB_CFG);
-- 
2.21.0