linux-kernel - Re: [PATCH] arm64: dts: imx8mp: add cpuidle state "cpu-pd-wait"

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Message-ID: <qqi2z7wutuy7e6o5fhpzsgfwkyn4quqmdeftl24meld72sudpg@lo3qpk4x7lbv>
Date: Mon, 14 Apr 2025 17:37:31 +0530
From: Jai Luthra <jai.luthra@...asonboard.com>
To: Catalin Popescu <catalin.popescu@...ca-geosystems.com>, 
	Shawn Guo <shawnguo2@...h.net>
Cc: robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org, 
	shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de, 
	festevam@...il.com, devicetree@...r.kernel.org, imx@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, m.felsch@...gutronix.de, 
	bsp-development.geo@...ca-geosystems.com, stefan.klug@...asonboard.com, laurent.pinchart@...asonboard.com
Subject: Re: [PATCH] arm64: dts: imx8mp: add cpuidle state "cpu-pd-wait"

Hi Catalin, Shawn,

On Oct 21, 2024 at 17:42:34 +0800, Shawn Guo wrote:
> On Mon, Oct 07, 2024 at 03:44:24PM +0200, Catalin Popescu wrote:
> > So far, only WFI is supported on i.MX8mp platform. Add support for
> > deeper cpuidle state "cpu-pd-wait" that would allow for better power
> > usage during runtime. This is a port from NXP downstream kernel.
> > 

Since the introduction of this patch in mainline, I am facing sluggish 
network performance with my Debix Model-A board with i.MX8mp SoC.

The network latency jumps to >1s after almost every other packet:

PING debix (10.0.42.5) 56(84) bytes of data.
64 bytes from debix (10.0.42.5): icmp_seq=1 ttl=64 time=1008 ms
64 bytes from debix (10.0.42.5): icmp_seq=2 ttl=64 time=0.488 ms
64 bytes from debix (10.0.42.5): icmp_seq=3 ttl=64 time=1025 ms
64 bytes from debix (10.0.42.5): icmp_seq=4 ttl=64 time=0.810 ms
64 bytes from debix (10.0.42.5): icmp_seq=5 ttl=64 time=590 ms
64 bytes from debix (10.0.42.5): icmp_seq=6 ttl=64 time=0.351 ms
^C
--- debix ping statistics ---
7 packets transmitted, 6 received, 14.2857% packet loss, time 6126ms
rtt min/avg/max/mdev = 0.351/437.416/1024.755/459.370 ms, pipe 2
darkapex at freya in ~

If I revert the patch, or disable the deeper cpuidle state through 
sysfs, the issue goes away.

# echo 1 > /sys/devices/system/cpu/cpu$i/cpuidle/state1/disable

PING debix (10.0.42.5) 56(84) bytes of data.
64 bytes from debix (10.0.42.5): icmp_seq=1 ttl=64 time=0.482 ms
64 bytes from debix (10.0.42.5): icmp_seq=2 ttl=64 time=2.28 ms
64 bytes from debix (10.0.42.5): icmp_seq=3 ttl=64 time=2.26 ms
64 bytes from debix (10.0.42.5): icmp_seq=4 ttl=64 time=0.848 ms
64 bytes from debix (10.0.42.5): icmp_seq=5 ttl=64 time=0.406 ms
^C
--- debix ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4051ms
rtt min/avg/max/mdev = 0.406/1.255/2.280/0.842 ms

> > Signed-off-by: Catalin Popescu 
> > <catalin.popescu@...ca-geosystems.com>
> 
> Applied, thanks!
> 
> 

Thanks,
Jai

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