-----Original Message-----
From: Mark Brown <broonie@kernel.org>
Sent: Thursday, October 28, 2021 7:50 PM
To: Richard Zhu <hongxing.zhu@nxp.com>
Cc: Francesco Dolcini <redacted>;
l.stach@pengutronix.de; bhelgaas@google.com;
lorenzo.pieralisi@arm.com; jingoohan1@gmail.com;
linux-pci@vger.kernel.org; dl-linux-imx [off-list ref];
linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org;
kernel@pengutronix.de
Subject: Re: [PATCH v3 3/7] PCI: imx6: Fix the regulator dump when link
never came up

On Thu, Oct 28, 2021 at 06:50:58AM +0000, Richard Zhu wrote:

quoted

quoted

I would be really surprised to see PCI hardware that was able to
support a supply being physically absent, and this use of
_is_enabled() is quite simply not how any of this is supposed to
work in the regulator API even for regulators that can be optional.

quoted

[Richard Zhu] Actually, this regulator is one GPIO fixed regulator.
Controlled by SW to turn on (GPIO high) or turn off (GPIO low) the

supply.

quoted

In some boards designs, this supply might be always on(GPIO high).
So, in point of SW driver view, this regulator is optional.

No, it's not.  The regulator API supports the systems where the regualtor
is always on perfectly well, the client driver should not need to do
anything to support them.

[Richard Zhu] Hi Mark: Thanks for your explains.
To disable the regulator explicitly, is a part of power save of i.MX PCIe port
 usage when link is down.
Because that this regulator might not be present at all on some boards
 (e.x: powered directly when board is powered up), so this regulator is
 optional from SW view.

quoted

quoted

Perhaps it's not causing problems in this design but if the supply
is ever shared with anything else then the software will run into

trouble.

quoted

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There will also be problems with the error handling on a system
where the regulator needs to be controlled.

quoted

[Richard Zhu] This GPIO fixed regulator is only used by controller driver.
It makes sense to disable the enabled regulator when driver probe is

failed.

The driver should undo any enables it did itself, it should not undo any
enables that anything else did which means it should never be basing
decisions on regulator_is_enabled().  While the regulator may not be
shared in the particular board you're looking at it may be shared in other
systems.

[Richard Zhu] Understood. Thanks.
Can I disabled this regulator in PCIe probe failure handler without the
 regulator_is_enabled() check?

BR
Richard

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