linux-kernel - Re: [PATCH v2] PCI: dw-rockchip: Enable async probe by default

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Message-ID: <Z3f95RXj7GhZZHEP@ryzen>
Date: Fri, 3 Jan 2025 16:10:29 +0100
From: Niklas Cassel <cassel@...nel.org>
To: Anand Moon <linux.amoon@...il.com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Heiko Stuebner <heiko@...ech.de>, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PCI: dw-rockchip: Enable async probe by default

On Fri, Jan 03, 2025 at 08:36:18PM +0530, Anand Moon wrote:
> > >
> > > We need to enable the GMAC PHY and reset it using the proper GPIO pin
> > > (PCIE_PERST_L).
> > > Please refer to the schematic for more details.
> >
> > The PERST# GPIO is already asserted + deasserted from the PCIe Root Complex
> > (host) driver:
> > https://github.com/torvalds/linux/blob/v6.13-rc5/drivers/pci/controller/dwc/pcie-dw-rockchip.c#L191-L206
> >
> > which will cause the endpoint device (a RTL8125 NIC in this case)
> > to be reset during bootup.
> >
> Thanks for letting me know. It seems like a workaround.
> I'll try to disable this and test it again.
> 
> My point is that we haven't enabled the GMAC PHY (device nodes)
> and must properly reset the GMAC.
> 
> We're relying on the code above hack to do that job.

I do not think it is a hack.

If you look in most PCIe controller drivers, they toggle PERST before
enumerating the bus:
$ git grep gpiod_set_value drivers/pci/controller/


Kind regards,
Niklas