4.14-stable review patch. If anyone has any objections, please let me know.
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From: Vaidyanathan Srinivasan svaidy@linux.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@samba.org Signed-off-by: Vaidyanathan Srinivasan svaidy@linux.vnet.ibm.com Reviewed-by: Gautham R. Shenoy ego@linux.vnet.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.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;