linux-kernel - [PATCH 4.9 25/53] memory: tegra: Fix integer overflow on tick value calculation

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Date:   Thu, 23 May 2019 21:05:49 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dmitry Osipenko <digetx@...il.com>,
        Thierry Reding <treding@...dia.com>
Subject: [PATCH 4.9 25/53] memory: tegra: Fix integer overflow on tick value calculation

From: Dmitry Osipenko <digetx@...il.com>

commit b906c056b6023c390f18347169071193fda57dde upstream.

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>
Signed-off-by: Thierry Reding <treding@...dia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/memory/tegra/mc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/memory/tegra/mc.c
+++ b/drivers/memory/tegra/mc.c
@@ -72,7 +72,7 @@ static int tegra_mc_setup_latency_allowa
 	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);