Re: [RFC PATCH v3 0/9] accel: rocket: Add RK3568 NPU support

From: Sebastian Reichel <sebastian.reichel@collabora.com>
To: Diederik de Haas <diederik@cknow-tech.com>
Cc: Midgy Balon <midgy971@gmail.com>,
	 Chaoyi Chen <chaoyi.chen@rock-chips.com>,
	tomeu@tomeuvizoso.net, ogabbay@kernel.org, heiko@sntech.de,
	 robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org,
	joro@8bytes.org,  will@kernel.org, robin.murphy@arm.com,
	dri-devel@lists.freedesktop.org,
	 linux-rockchip@lists.infradead.org, devicetree@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,  iommu@lists.linux.dev,
	linux-kernel@vger.kernel.org, Simon Xue <xxm@rock-chips.com>,
	 Finley Xiao <finley.xiao@rock-chips.com>,
	Jonas Karlman <jonas@kwiboo.se>
Subject: Re: [RFC PATCH v3 0/9] accel: rocket: Add RK3568 NPU support
Date: Fri, 12 Jun 2026 23:15:34 +0200	[thread overview]
Message-ID: <aixze8zFboY3huSf@venus> (raw)
In-Reply-To: <DJ5FUW50YM2N.6ZTY4WK27ZP5@cknow-tech.com>

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Hi,

On Wed, Jun 10, 2026 at 04:28:17PM +0200, Diederik de Haas wrote:
> On Wed Jun 10, 2026 at 3:36 PM CEST, Midgy Balon wrote:
> [    2.110935] rockchip-pm-domain fd8d8000.power-management:power-controller: Failed to create device link (0x180) with supplier 2-0042 for /power-management@fd8d8000/power-controller/power-domain@8
> [    2.557459] sdhci-dwcmshc fe2e0000.mmc: Can't reduce the clock below 52MHz in HS200/HS400 mode
> [    2.647174] rockchip-pm-domain fd8d8000.power-management:power-controller: Failed to create device link (0x180) with supplier 2-0042 for /power-management@fd8d8000/power-controller/power-domain@8
> [    2.945089] rockchip-pm-domain fd8d8000.power-management:power-controller: Failed to create device link (0x180) with supplier spi2.0 for /power-management@fd8d8000/power-controller/power-domain@12
> 
> 8 = NPU; 12 = GPU
> 
> on both nanopc-t6-lts and nanopc-t6-plus (both RK3588).
> And on a 6.18 dmesg output I have for Rock 5B, I see the ~ same, but then
> it's 1-0042 instead of 2-0042. 
> 
> I don't know if it's bad or harmless, but it is consistent.

The fw_devlink framework tries to figure out a sensible probe order
by analyzing links between devices. The warning is because there is
a cyclic dependency. This happens because all power domains are
provided by one device (power-controller).

Now if you want to probe the I2C regulator 2-0042, you need the
I2C controller and to probe the I2C controller you need the I2C
power domain and for that you need the power-controller. But for
the power-controller you need 2-0042 (for the NPU power-domain).
At this point fw_devlink gives up and prints the warning.

Apart from the warning this results in the kernel missing dependency
information, so there might be some extra probe calls ending in
-EPROBE_DEFER (which wastes CPU power and delays the boot process).

So it's neither super bad, nor completely harmless. Fixing this
properly requires some heavy restructuring of the Rockchip
power-controller driver.

Greetings,

-- Sebastian

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