linux-kernel - [PATCH 4.14 154/164] powerpc/powernv/idle: Round up latency and residency values

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Date:   Tue, 12 Dec 2017 13:45:34 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Anton Blanchard <anton@...ba.org>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.14 154/164] powerpc/powernv/idle: Round up latency and residency values

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/cpuidle/cpuidle-powernv.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- 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;