linux-kernel - Re: [PATCH v9 5/8] PCI: imx6: Refine the regulator usage

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Date:   Thu, 9 Jun 2022 12:20:05 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Hongxing Zhu <hongxing.zhu@....com>
Cc:     "l.stach@...gutronix.de" <l.stach@...gutronix.de>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "jingoohan1@...il.com" <jingoohan1@...il.com>,
        "festevam@...il.com" <festevam@...il.com>,
        "francesco.dolcini@...adex.com" <francesco.dolcini@...adex.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH v9 5/8] PCI: imx6: Refine the regulator usage

On Thu, Jun 09, 2022 at 06:19:47AM +0000, Hongxing Zhu wrote:
> > -----Original Message-----
> > From: Bjorn Helgaas <helgaas@...nel.org>
> > Sent: 2022年6月9日 2:55
> > To: Hongxing Zhu <hongxing.zhu@....com>
> > Cc: l.stach@...gutronix.de; bhelgaas@...gle.com; robh+dt@...nel.org;
> > 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; dl-linux-imx
> > <linux-imx@....com>
> > Subject: Re: [PATCH v9 5/8] PCI: imx6: Refine the regulator usage
> > 
> > On Fri, May 06, 2022 at 09:47:06AM +0800, Richard Zhu wrote:
> > > The driver should undo any enables it did itself. The regulator
> > > disable shouldn't be basing decisions on regulator_is_enabled().

The driver should disable things if an error occurs after it has
enabled something, or if it enabled something during probe and we're
now detaching the driver.  That doesn't look like the case here.

> > > To keep the balance of the regulator usage counter, disable the
> > > regulator just behind of imx6_pcie_assert_core_reset() in resume and
> > > shutdown.
> > 
> > In subject, "Refine" doesn't tell me anything about what's happening here.
>
> Thanks for your comments.
> How about the following one?
> PCI: imx6: Do regulator disable without the regulator_is_enabled check

That's too low-level, like describing the C code line by line.
I'm hoping for something about the purpose for the patch so
"git log --oneline" can tell a coherent story.

Apparently this is about disabling the power regulator when the slot
isn't being used, so maybe it could say something about that.

  $ git grep -Ep "regulator_(en|dis)able" drivers/pci/controller/

shows that in other drivers, this being done in
probe/remove/suspend/resume-type paths.  imx6 should be similar.

Bjorn