linux-kernel - [PATCH AUTOSEL for 4.14 55/64] powerpc/powernv/idle: Round up latency and residency values

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Message-ID: <20171202155101.7573-55-alexander.levin@verizon.com>
Date:   Sat, 2 Dec 2017 15:51:39 +0000
From:   alexander.levin@...izon.com
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        alexander.levin@...izon.com
Subject: [PATCH AUTOSEL for 4.14 55/64] powerpc/powernv/idle: Round up latency
 and residency values

From: Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>

[ Upstream commit 8d4e10e9ed9450e18fbbf6a8872be0eac9fd4999 ]

On PowerNV platforms, firmware provides exit latency and
target residency for each of the idle states in nano
seconds.  Cpuidle framework expects the values in micro
seconds.  Round up to nearest micro seconds to avoid errors
in cases where the values are defined as fractional micro
seconds.

Default idle state of 'snooze' has exit latency of zero.  If
other states have fractional micro second exit latency, they
would get rounded down to zero micro second and make cpuidle
framework choose deeper idle state when snooze loop is the
right choice.

Reported-by: Anton Blanchard <anton@...ba.org>
Signed-off-by: Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
Reviewed-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
---
 drivers/cpuidle/cpuidle-powernv.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
index ed6531f075c6..e06605b21841 100644
--- a/drivers/cpuidle/cpuidle-powernv.c
+++ b/drivers/cpuidle/cpuidle-powernv.c
@@ -384,9 +384,9 @@ static int powernv_add_idle_states(void)
 		 * Firmware passes residency and latency values in ns.
 		 * cpuidle expects it in us.
 		 */
-		exit_latency = latency_ns[i] / 1000;
+		exit_latency = DIV_ROUND_UP(latency_ns[i], 1000);
 		if (!rc)
-			target_residency = residency_ns[i] / 1000;
+			target_residency = DIV_ROUND_UP(residency_ns[i], 1000);
 		else
 			target_residency = 0;
 
-- 
2.11.0