> -----Original Message----- > From: Mark Brown <broonie@xxxxxxxxxx> > Sent: Thursday, October 28, 2021 7:50 PM > To: Richard Zhu <hongxing.zhu@xxxxxxx> > Cc: Francesco Dolcini <francesco.dolcini@xxxxxxxxxxx>; > l.stach@xxxxxxxxxxxxxx; bhelgaas@xxxxxxxxxx; > lorenzo.pieralisi@xxxxxxx; jingoohan1@xxxxxxxxx; > linux-pci@xxxxxxxxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>; > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > kernel@xxxxxxxxxxxxxx > 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: > > > > 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. > > > [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. > > 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. > > > > 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. > > > There will also be problems with the error handling on a system > > > where the regulator needs to be controlled. > > > [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
