From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
To: sophon@radxa.com, Bjorn Helgaas <bhelgaas@google.com>,
Andrzej Hajda <andrzej.hajda@intel.com>,
Neil Armstrong <neil.armstrong@linaro.org>,
Robert Foss <rfoss@kernel.org>,
Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
Jonas Karlman <jonas@kwiboo.se>,
Jernej Skrabec <jernej.skrabec@gmail.com>,
Luca Ceresoli <luca.ceresoli@bootlin.com>,
David Airlie <airlied@gmail.com>, Simona Vetter <simona@ffwll.ch>,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Maxime Ripard <mripard@kernel.org>,
Thomas Zimmermann <tzimmermann@suse.de>,
Rob Herring <robh@kernel.org>,
Krzysztof Kozlowski <krzk+dt@kernel.org>,
Conor Dooley <conor+dt@kernel.org>,
Bjorn Andersson <andersson@kernel.org>,
Konrad Dybcio <konradybcio@kernel.org>,
Bartosz Golaszewski <brgl@kernel.org>,
Linus Walleij <linusw@kernel.org>
Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org,
linux-arm-msm@vger.kernel.org, linux-gpio@vger.kernel.org,
Stephen Chen <stephen@radxa.com>, Junhao Xie <bigfoot@radxa.com>
Subject: Re: [PATCH 1/6] PCI: of: Avoid config reads for disabled bridge nodes
Date: Thu, 3 Sep 2026 16:40:44 +0200 [thread overview]
Message-ID: <a5d83aa4-7065-47c0-bbda-35063034b0d6@oss.qualcomm.com> (raw)
In-Reply-To: <B4EB99E5B76C9F40+e6fdbdd4-5c05-4b98-867c-29c7178a0d72@radxa.com>
On 9/2/26 11:31 AM, Xilin Wu wrote:
> On 9/2/2026 4:43 PM, Konrad Dybcio wrote:
>> On 9/1/26 10:47 AM, Xilin Wu wrote:
>>> The TC9563 PCI power-control driver powers off external downstream ports
>>> whose device tree nodes have status = "disabled".
>>>
>>> On the Radxa Dragon Q8B, reading the Vendor ID from one of these
>>> powered-off port functions during PCI enumeration raises an Arm SError
>>> instead of returning an all-ones PCI error response. This prevents the
>>> board from completing boot.
>>
>> I agree with the premise of the patch, but I'd like to understand why
>> that happens - do you have any details?
>
> Unfortunately, I don't have further details. The downstream kernel also includes a similar workaround, so I suspect it's related to how the TC9563 chip is designed.
I'm curious in why the port is still advertised on the bus if
the i2c interface writes some magic bits to "disable" it on the IC
side.. but perhaps that's just how that IC behaves and we can't
do anything about it?
Konrad
next prev parent reply other threads:[~2026-09-03 14:40 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-01 8:47 [PATCH 0/6] arm64: dts: qcom: Add support for Radxa Dragon Q8B Xilin Wu
2026-09-01 8:47 ` [PATCH 1/6] PCI: of: Avoid config reads for disabled bridge nodes Xilin Wu
2026-09-01 8:55 ` sashiko-bot
2026-09-02 8:43 ` Konrad Dybcio
2026-09-02 9:31 ` Xilin Wu
2026-09-03 14:40 ` Konrad Dybcio [this message]
2026-09-03 14:41 ` Xilin Wu
2026-09-01 8:47 ` [PATCH 2/6] dt-bindings: display: bridge: simple: document Chrontel CH7218A Xilin Wu
2026-09-01 8:52 ` sashiko-bot
2026-09-03 12:29 ` Krzysztof Kozlowski
2026-09-01 8:47 ` [PATCH 3/6] drm/bridge: simple: add " Xilin Wu
2026-09-01 8:51 ` sashiko-bot
2026-09-01 8:47 ` [PATCH 4/6] dt-bindings: arm: qcom: document Radxa Dragon Q8B Xilin Wu
2026-09-01 8:52 ` sashiko-bot
2026-09-03 12:36 ` Krzysztof Kozlowski
2026-09-01 8:47 ` [PATCH 5/6] dt-bindings: pinctrl: qcom,sc8280xp-tlmm: allow gpio-line-names Xilin Wu
2026-09-01 8:55 ` sashiko-bot
2026-09-01 14:17 ` Konrad Dybcio
2026-09-03 12:35 ` Krzysztof Kozlowski
2026-09-01 8:47 ` [PATCH 6/6] arm64: dts: qcom: sc8280xp: add Radxa Dragon Q8B Xilin Wu
2026-09-01 9:05 ` sashiko-bot
2026-09-03 11:00 ` [PATCH 0/6] arm64: dts: qcom: Add support for " Daniele Briguglio
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