RE: [PATCH v8 5/8] PCI: imx6: Refine the regulator usage

-----Original Message-----
From: Francesco Dolcini <redacted>
Sent: 2022年3月4日 15:46
To: Hongxing Zhu <hongxing.zhu@nxp.com>
Cc: Francesco Dolcini <redacted>;
l.stach@pengutronix.de; bhelgaas@google.com; broonie@kernel.org;
lorenzo.pieralisi@arm.com; jingoohan1@gmail.com; festevam@gmail.com;
linux-pci@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
linux-kernel@vger.kernel.org; kernel@pengutronix.de; dl-linux-imx
[off-list ref]
Subject: Re: [PATCH v8 5/8] PCI: imx6: Refine the regulator usage

On Mon, Feb 28, 2022 at 03:43:03AM +0000, Hongxing Zhu wrote:

quoted

quoted

2. We are playing around with vpcie during regulator during
suspend/resume, why? We currently have issue with suspend/resume
when a PCIe switch is there, with the final effect of PCIe being not
usable afterward. I fear like this is related to our issue.

To my understands, the VPCIE is the abstract of the DIESABLE# signal.
Refer to the Chapter 3.1.12.3 W_DISABLE# Signal of PCI Express M.2 SPEC.
These signals are used to disable the Adapter's radio operation to
meet public Safety regulations or when otherwise desired.
It's reasonable to assert/de-assert W_DISABLE# signal during

suspend/resume.

quoted

quoted

What about vpcie enable in probe, and vpcie disable in shutdown and
that's all?

The W_DISABLE# Signal is used to control the radios on the Adapters.
I think you can do that, if the radios are always on in your system.

According to the binding documentation (imx6q-pcie.yaml)

  vpcie-supply:
    description: Should specify the regulator in charge of PCIe port power.
      The regulator will be enabled when initializing the PCIe host and
      disabled either as part of the init process or when shutting down
      the host (optional required).

This is how it's documented to be used, if this is used according to the
documentation (and this is happening) what you are already doing (not
changed in this patch, you are right) is not correct.

Abusing this for the W_DISABLE# disable is new to me and does not look legit.

The vpcie-supply is one gpio regulator actually, used to control remote Endpoint
 device, through the DISABLE# signal (defined in Mini CEM/M.2 SPEC) of the port.

Best Regards
Richard Zhu

Francesco

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel