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

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Message-ID: <20250415154724.GG9439@pendragon.ideasonboard.com>
Date: Tue, 15 Apr 2025 18:47:24 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: POPESCU Catalin <catalin.popescu@...ca-geosystems.com>
Cc: Jai Luthra <jai.luthra@...asonboard.com>,
	Shawn Guo <shawnguo2@...h.net>, "robh@...nel.org" <robh@...nel.org>,
	"krzk+dt@...nel.org" <krzk+dt@...nel.org>,
	"conor+dt@...nel.org" <conor+dt@...nel.org>,
	"shawnguo@...nel.org" <shawnguo@...nel.org>,
	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>,
	"festevam@...il.com" <festevam@...il.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"m.felsch@...gutronix.de" <m.felsch@...gutronix.de>,
	GEO-CHHER-bsp-development <bsp-development.geo@...ca-geosystems.com>,
	"stefan.klug@...asonboard.com" <stefan.klug@...asonboard.com>
Subject: Re: [PATCH] arm64: dts: imx8mp: add cpuidle state "cpu-pd-wait"

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) ?

> 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@...ca-geosystems.com>
> >>
> >> Applied, thanks!

-- 
Regards,

Laurent Pinchart