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

[Laurent Pinchart]

Hi Catalin,

On Wed, Apr 16, 2025 at 06:57:35AM +0000, POPESCU Catalin wrote:
> On 15/04/2025 17:52, Laurent Pinchart wrote:
> > On Tue, Apr 15, 2025 at 06:47:26PM +0300, Laurent Pinchart wrote:
> >> 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 :-)
> 
> Bonjour Laurent,
> 
> I'm running a yocto scarthgap custom build :
> 
> - barebox : http://barebox.org/download/barebox-2024.05.0.tar.bz2 _with_
> custom patches
> - kernel : 6.12.16 _with_ custom patches
> - TF-A :
> git://github.com/hexagon-geo-surv/trusted-firmware-a;protocol=https;branch=leica/v2.12
> / SRCREV=46c962c654de4ab734f936f472508edf20c6c049 (_no_ custom patches)

Could you please run tests with the latest mainline kernel ?

> > 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 at leica-geosystems.com>
> >>>>> Applied, thanks!

-- 
Regards,

Laurent Pinchart