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

From: Niklas Cassel <cassel@kernel.org>
To: Anand Moon <linux.amoon@gmail.com>
Cc: "Manivannan Sadhasivam" <manivannan.sadhasivam@linaro.org>,
	"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
	"Krzysztof Wilczyński" <kw@linux.com>,
	"Rob Herring" <robh@kernel.org>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Heiko Stuebner" <heiko@sntech.de>,
	linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] PCI: dw-rockchip: Enable async probe by default
Date: Fri, 3 Jan 2025 16:10:29 +0100	[thread overview]
Message-ID: <Z3f95RXj7GhZZHEP@ryzen> (raw)
In-Reply-To: <CANAwSgRTcHuDNLvPJAs7ZaV-NnepeOkHj_kVc5OAJtP03hd6pQ@mail.gmail.com>

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