linux-kernel - Re: [PATCH v1 0/3] PCI: imx6: reset link after suspend/resume

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Message-ID: <ZsQ9OWdCS5o96VN2@eichest-laptop>
Date: Tue, 20 Aug 2024 08:52:41 +0200
From: Stefan Eichenberger <eichest@...il.com>
To: Frank Li <Frank.li@....com>
Cc: hongxing.zhu@....com, l.stach@...gutronix.de, lpieralisi@...nel.org,
	kw@...ux.com, robh@...nel.org, bhelgaas@...gle.com,
	shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de,
	festevam@...il.com, francesco.dolcini@...adex.com,
	linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	imx@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 0/3] PCI: imx6: reset link after suspend/resume

On Mon, Aug 19, 2024 at 10:30:38AM -0400, Frank Li wrote:
> On Mon, Aug 19, 2024 at 11:03:16AM +0200, Stefan Eichenberger wrote:
> > On the i.MX6Quad (not QuadPlus), the PCIe link does not work after a
> > suspend/resume cycle. Worse, the PCIe memory mapped I/O isn't accessible
> > at all, so the system freezes when a PCIe driver tries to access its I/O
> > space. The only way to get resume working again is to reset the PCIe
> > link, similar to what is done on devices that support suspend/resume.
> > Through trial and error, we found that something about the PCIe
> > reference clock does not work as expected after a resume. We could not
> > figure out if it is disabled (even though the registers still say it is
> > enabled), or if it is somehow unstable or has some hiccups. With the
> > workaround introduced in this patch series, we were able to fully resume
> > a Compex WLE900VX (ath10k) miniPCIe Wifi module and an Intel AX200 M.2
> > Wifi module. If there is a better way or other ideas on how to fix this
> > problem, please let us know. We are aware that resetting the link should
> > not be necessary, but we could not find a better solution. More
> > interestingly, even the SoCs that support suspend/resume according to
> > the i.MX erratas seem to reset the link on resume in
> > imx6_pcie_host_init, so we hope this might be a valid workaround.
> >
> > Stefan Eichenberger (3):
> >   PCI: imx6: Add a function to deassert the reset gpio
> >   PCI: imx6: move the wait for clock stabilization to enable ref clk
> >   PCI: imx6: reset link on resume
> 
> Thanks you for your patch, but it may have conflict with
> https://lore.kernel.org/linux-pci/Zr4XG6r+HnbIlu8S@lizhi-Precision-Tower-5810/T/#t
> 

Thanks a lot for the hint. I will have a look at the series and see if I
can adapt my changes including your suggestions.

Regards,
Stefan