Re: [PATCH 2/2] PCI: meson: Add missing remove callback

From: Shuvam Pandey <shuvampandey1@gmail.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: "Jingoo Han" <jingoohan1@gmail.com>,
	"Manivannan Sadhasivam" <mani@kernel.org>,
	"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
	"Krzysztof Wilczyński" <kwilczynski@kernel.org>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Yue Wang" <yue.wang@amlogic.com>,
	"Neil Armstrong" <neil.armstrong@linaro.org>,
	"Rob Herring" <robh@kernel.org>,
	"Kevin Hilman" <khilman@baylibre.com>,
	"Jerome Brunet" <jbrunet@baylibre.com>,
	"Martin Blumenstingl" <martin.blumenstingl@googlemail.com>,
	"Fan Ni" <fan.ni@samsung.com>,
	"Shradha Todi" <shradha.t@samsung.com>,
	"Hanjie Lin" <hanjie.lin@amlogic.com>,
	linux-pci@vger.kernel.org, linux-amlogic@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] PCI: meson: Add missing remove callback
Date: Fri, 12 Jun 2026 20:24:56 +0545	[thread overview]
Message-ID: <CANAAWH+qT8T4_OBwu0WxU6o0FTT7xqwpLTOFrWiV1dZbXHk+fw@mail.gmail.com> (raw)
In-Reply-To: <20260611222653.GA527114@bhelgaas>

Hi Bjorn,

> What's the user-visible effect of this?  Does it avoid an oops?
> Reduce power usage?

I don't have hardware with this controller, so I have not observed an
oops from this.

The concrete effect is that driver unbind/module unload gets the
matching teardown for the successful probe path: the DesignWare host
bridge is unregistered with dw_pcie_host_deinit(), and the PHY is
powered off with meson_pcie_power_off() before devres releases the
driver's resources.

So yes, it should reduce power usage after unbind. The host bridge
teardown is also the matching cleanup for dw_pcie_host_init(), but I
don't have hardware evidence of an oops on unbind.

> Of the 34 instances of .probe() in drivers/pci/controller/dwc/, on 12
> implement .remove(), so if this fixes a problem, I'm wondering whether
> other drivers have the same problem.

Yes, that may deserve a broader driver-by-driver audit. I only checked
Meson for this patch. Some DWC drivers implement .remove(), and several
others set .suppress_bind_attrs, which affects the manual sysfs
bind/unbind path. Before this patch, the Meson driver had neither, while
meson_pcie_probe() calls meson_pcie_power_on() and registers the host
bridge with dw_pcie_host_init().

Thanks,
Shuvam

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