From: Richard Zhu <hongxing.zhu@nxp.com>
To: Mark Brown <broonie@kernel.org>
Cc: Francesco Dolcini <francesco.dolcini@toradex.com>,
"l.stach@pengutronix.de" <l.stach@pengutronix.de>,
"bhelgaas@google.com" <bhelgaas@google.com>,
"lorenzo.pieralisi@arm.com" <lorenzo.pieralisi@arm.com>,
"jingoohan1@gmail.com" <jingoohan1@gmail.com>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
dl-linux-imx <linux-imx@nxp.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kernel@pengutronix.de" <kernel@pengutronix.de>
Subject: RE: [PATCH v3 3/7] PCI: imx6: Fix the regulator dump when link never came up
Date: Fri, 29 Oct 2021 03:58:41 +0000 [thread overview]
Message-ID: <AS8PR04MB8676CF52F4D8E9E4E6C07F758C879@AS8PR04MB8676.eurprd04.prod.outlook.com> (raw)
In-Reply-To: <YXqOcAIO2aYkr1sM@sirena.org.uk>
> -----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 <francesco.dolcini@toradex.com>;
> l.stach@pengutronix.de; bhelgaas@google.com;
> lorenzo.pieralisi@arm.com; jingoohan1@gmail.com;
> linux-pci@vger.kernel.org; dl-linux-imx <linux-imx@nxp.com>;
> 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:
>
> > > 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
next prev parent reply other threads:[~2021-10-29 3:58 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-22 7:12 [PATCH v3 0/7] PCI: imx6: refine codes and add compliance tests mode support Richard Zhu
2021-10-22 7:12 ` [PATCH v3 1/7] PCI: imx6: Encapsulate the clock enable into one standalone function Richard Zhu
2021-10-22 7:12 ` [PATCH v3 2/7] PCI: imx6: Add the error propagation from host_init Richard Zhu
2021-10-22 7:12 ` [PATCH v3 3/7] PCI: imx6: Fix the regulator dump when link never came up Richard Zhu
2021-10-25 11:13 ` Francesco Dolcini
2021-10-25 11:23 ` Mark Brown
2021-10-26 2:18 ` Richard Zhu
2021-10-26 8:52 ` Francesco Dolcini
2021-10-26 9:06 ` Richard Zhu
2021-10-26 9:11 ` Francesco Dolcini
2021-10-26 9:18 ` Richard Zhu
2021-10-26 9:48 ` Francesco Dolcini
2021-10-28 6:48 ` Richard Zhu
2021-10-26 10:58 ` Mark Brown
2021-10-28 6:50 ` Richard Zhu
2021-10-28 11:50 ` Mark Brown
2021-10-29 3:58 ` Richard Zhu [this message]
2021-10-29 11:46 ` Mark Brown
2021-11-01 1:46 ` Richard Zhu
2021-10-26 1:57 ` Richard Zhu
2021-10-22 7:12 ` [PATCH v3 4/7] PCI: imx6: move the clock disable function to a proper place Richard Zhu
2021-10-22 7:12 ` [PATCH v3 5/7] PCI: dwc: add a new callback host exit function into host ops Richard Zhu
2021-10-22 7:12 ` [PATCH v3 6/7] PCI: imx6: Fix the reference handling unbalance when link never came up Richard Zhu
2021-10-22 7:12 ` [PATCH v3 7/7] PCI: imx6: Add the compliance tests mode support Richard Zhu
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