linux-kernel - RE: [PATCH v10 5/7] PCI: imx6: Turn off regulator when the system is in suspend mode

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Date:   Tue, 14 Jun 2022 00:58:34 +0000
From:   Hongxing Zhu <hongxing.zhu@....com>
To:     Francesco Dolcini <francesco.dolcini@...adex.com>,
        "l.stach@...gutronix.de" <l.stach@...gutronix.de>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "robh@...nel.org" <robh@...nel.org>
CC:     "broonie@...nel.org" <broonie@...nel.org>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "festevam@...il.com" <festevam@...il.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 v10 5/7] PCI: imx6: Turn off regulator when the system is
 in suspend mode

> -----Original Message-----
> From: Francesco Dolcini <francesco.dolcini@...adex.com>
> Sent: 2022年6月13日 18:17
> To: Hongxing Zhu <hongxing.zhu@....com>; l.stach@...gutronix.de;
> bhelgaas@...gle.com; robh@...nel.org
> Cc: broonie@...nel.org; lorenzo.pieralisi@....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 v10 5/7] PCI: imx6: Turn off regulator when the system is
> in suspend mode
> 
> On Mon, Jun 13, 2022 at 04:55:36PM +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().
> >
> > Move the regulator_disable to the suspend function, turn off regulator
> > when the system is in suspend mode.
> 
> According to the documentation:
> 
>   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).
> 
> Is this really what we want to do (remove power in suspend, enable it on
> resume)? On our boards this powers a PCIe device connected to the host port,
> that sound fair according to the binding documentation for it.
> Am I wrong?
> 
> We do have issues with PCIe not working anymore after suspend/resume,
> wondering (I did not have time to properly dig into it) if this is the root cause.
> 
Hi Francesco:
Yes, you're right. This regulator is used to powered up the port. It's
 reasonable to move the disable to suspend refer to Lucas' review comments.
BTW, I suspect that your PCIe failure after suspend/resume is caused by the
 MSI_ADDR missing. Can you make a double check on it?
I used found that the MSI_ADDR should be re-configured again during resume on
 some platforms. But I didn't issue that fix patch in time. Sorry about that.

Best Regards
Richard Zhu

> Francesco