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

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Tue, Apr 15, 2025 at 06:47:26PM +0300, Laurent Pinchart wrote:
> Hi Catalin,
> 
> On Tue, Apr 15, 2025 at 03:42:22PM +0000, POPESCU Catalin wrote:
> > Hi Jai,
> > 
> > This issue was already reported by Stefan. The problem is that I don't 
> > have a Debix board to investigate.
> > The main difference b/w WFI and cpu-pd-wait is that the first doesn't 
> > call PSCI/TF-A. So, the issue looks to be related to some settings in 
> > the TF-A.
> 
> Jai, are you using mainline U-Boot and TF-A, or a downstream version of
> either (or both) ?

Actually, same question for Calatin :-)

I'm running mainline U-Boot 2025.01 and TF-A rel_imx_5.4.70_2.3.6 (from
https://github.com/nxp-imx/imx-atf) and don't seem to experience the
issue:

# cat /sys/devices/system/cpu/cpu*/cpuidle/state1/disable
0
0
0
0

$ ping debix
PING debix.farm.ideasonboard.com (192.168.2.230) 56(84) bytes of data.
64 bytes from debix.farm.ideasonboard.com (192.168.2.230): icmp_seq=1 ttl=64 time=1.03 ms
64 bytes from debix.farm.ideasonboard.com (192.168.2.230): icmp_seq=2 ttl=64 time=0.800 ms
64 bytes from debix.farm.ideasonboard.com (192.168.2.230): icmp_seq=3 ttl=64 time=0.935 ms
64 bytes from debix.farm.ideasonboard.com (192.168.2.230): icmp_seq=4 ttl=64 time=0.902 ms
64 bytes from debix.farm.ideasonboard.com (192.168.2.230): icmp_seq=5 ttl=64 time=0.738 ms
64 bytes from debix.farm.ideasonboard.com (192.168.2.230): icmp_seq=6 ttl=64 time=0.939 ms

> > What I don't get is why I don't see this issue neither on our IMX8MP 
> > specific design nor on the EVK, which uses the same PHY as the Debix board.
> >
> > On 14/04/2025 14:07, Jai Luthra wrote:
> > > 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@leica-geosystems.com>
> > >>
> > >> Applied, thanks!

-- 
Regards,

Laurent Pinchart