linux-kernel - Re: [PATCH v8 8/8] PCI: imx6: Add compliance tests mode support

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Date:   Fri, 1 Apr 2022 15:26:33 -0500
From:   Rob Herring <robh@...nel.org>
To:     Richard Zhu <hongxing.zhu@....com>
Cc:     l.stach@...gutronix.de, bhelgaas@...gle.com, broonie@...nel.org,
        lorenzo.pieralisi@....com, jingoohan1@...il.com,
        festevam@...il.com, francesco.dolcini@...adex.com,
        linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, kernel@...gutronix.de,
        linux-imx@....com
Subject: Re: [PATCH v8 8/8] PCI: imx6: Add compliance tests mode support

On Fri, Feb 25, 2022 at 11:44:27AM +0800, Richard Zhu wrote:
> Refer to the Chapter 3.2 System Board Signal Quality of PCI Express
> Architecture PHY Test Specification Revision 2.0.
> 
> Signal quality tests (for example: jitter, differential eye opening and
> so on) can be executed with devices in the polling.compliance state.
> 
> To let the device support polling.compliance state, the clocks and powers
> shouldn't be turned off when the probe of device driver fails.
> 
> Based on CLB (Compliance Load Board) Test Fixture and so on test
> equipments, the PHY link would be down during the compliance tests.
> Refer to this scenario, add the i.MX PCIe compliance tests mode enable
> support, and keep the clocks and powers on, and finish the driver probe
> without error return.

How is this specific to i.MX? If there's a need for compliance test 
mode, then shouldn't it be common? However, while your usecase is 
compliance testing, there doesn't seem to be any need for the kernel to 
know what the usecase is.

In the same series you've argued both ways. You need the driver to probe 
successfully with no link and you need it to shutdown on no link.

> 
> Use the "pci_imx6.compliance=1" in kernel command line to enable the
> compliance tests mode.
> 
> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 47 ++++++++++++++++++---------
>  1 file changed, 31 insertions(+), 16 deletions(-)