linux-kernel - RE: [PATCH v14 14/17] PCI: imx6: Do not hide phy driver callbacks and refine the error handling

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Date:   Wed, 13 Jul 2022 12:52:31 +0000
From:   Hongxing Zhu <hongxing.zhu@....com>
To:     Lucas Stach <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>,
        "festevam@...il.com" <festevam@...il.com>,
        "francesco.dolcini@...adex.com" <francesco.dolcini@...adex.com>
CC:     "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 v14 14/17] PCI: imx6: Do not hide phy driver callbacks and
 refine the error handling

> -----Original Message-----
> From: Lucas Stach <l.stach@...gutronix.de>
> Sent: 2022年7月13日 19:17
> To: Hongxing Zhu <hongxing.zhu@....com>; bhelgaas@...gle.com;
> robh+dt@...nel.org; broonie@...nel.org; lorenzo.pieralisi@....com;
> festevam@...il.com; francesco.dolcini@...adex.com
> Cc: 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 v14 14/17] PCI: imx6: Do not hide phy driver callbacks and
> refine the error handling
> 
> Am Mittwoch, dem 13.07.2022 um 10:57 +0000 schrieb Hongxing Zhu:
> > > -----Original Message-----
> > > From: Lucas Stach <l.stach@...gutronix.de>
> > > Sent: 2022年7月13日 16:59
> > > To: Hongxing Zhu <hongxing.zhu@....com>; bhelgaas@...gle.com;
> > > robh+dt@...nel.org; broonie@...nel.org; lorenzo.pieralisi@....com;
> > > festevam@...il.com; francesco.dolcini@...adex.com
> > > Cc: 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 v14 14/17] PCI: imx6: Do not hide phy driver
> > > callbacks and refine the error handling
> > >
> > > Am Freitag, dem 01.07.2022 um 11:25 +0800 schrieb Richard Zhu:
> > > > - Move the phy_power_on() to host_init from
> > > > imx6_pcie_clk_enable().
> > > > - Move the phy_init() to host_init from
> > > > imx6_pcie_deassert_core_reset().
> > > >
> > > > Refine the error handling in imx6_pcie_host_init() accordingly.
> > > >
> > > > Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> > > > Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
> > > > ---
> > > >  drivers/pci/controller/dwc/pci-imx6.c | 34 +++++++++++++++++----
> > > > ------
> > > >  1 file changed, 21 insertions(+), 13 deletions(-)
> > > >
> > > > diff --git a/drivers/pci/controller/dwc/pci-imx6.c
> > > b/drivers/pci/controller/dwc/pci-imx6.c
> > > > index 5a06fbca82d6..0b2a5256fb0d 100644
> > > > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > > > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > > > @@ -639,14 +639,6 @@ static int imx6_pcie_clk_enable(struct
> > > > imx6_pcie
> > > *imx6_pcie)
> > > >  		goto err_ref_clk;
> > > >  	}
> > > >
> > > > -	switch (imx6_pcie->drvdata->variant) {
> > > > -	case IMX8MM:
> > > > -		if (phy_power_on(imx6_pcie->phy))
> > > > -			dev_err(dev, "unable to power on
> > > > PHY\n");
> > > > -		break;
> > > > -	default:
> > > > -		break;
> > > > -	}
> > > >  	/* allow the clocks to stabilize */
> > > >  	usleep_range(200, 500);
> > > >  	return 0;
> > > > @@ -723,10 +715,6 @@ static int
> > > > imx6_pcie_deassert_core_reset(struct
> > > imx6_pcie *imx6_pcie)
> > > >  	case IMX8MQ:
> > > >  		reset_control_deassert(imx6_pcie-
> > > > >pciephy_reset);
> > > >  		break;
> > > > -	case IMX8MM:
> > > > -		if (phy_init(imx6_pcie->phy))
> > > > -			dev_err(dev, "waiting for phy ready
> > > > timeout!\n");
> > > > -		break;
> > > >  	case IMX7D:
> > > >  		reset_control_deassert(imx6_pcie-
> > > > >pciephy_reset);
> > > >
> > > > @@ -762,6 +750,7 @@ static int
> > > > imx6_pcie_deassert_core_reset(struct
> > > imx6_pcie *imx6_pcie)
> > > >  		usleep_range(200, 500);
> > > >  		break;
> > > >  	case IMX6Q:		/* Nothing to do */
> > > > +	case IMX8MM:
> > > >  		break;
> > > >  	}
> > > >
> > > > @@ -913,17 +902,36 @@ static int imx6_pcie_host_init(struct
> > > > pcie_port
> > > *pp)
> > > >  			return ret;
> > > >  		}
> > > >  	}
> > > > +	if (imx6_pcie->phy) {
> > > > +		ret = phy_power_on(imx6_pcie->phy);
> > > > +		if (ret) {
> > > > +			dev_err(dev, "pcie phy power up
> > > > failed.\n");
> > > > +			goto err_reg_disable;
> > > > +		}
> > > > +	}
> > > >
> > > >  	ret = imx6_pcie_deassert_core_reset(imx6_pcie);
> > > >  	if (ret < 0) {
> > > >  		dev_err(dev, "pcie deassert core reset failed:
> > > > %d\n", ret);
> > > > -		goto err_reg_disable;
> > > > +		goto err_phy_off;
> > > >  	}
> > > >
> > > > +	if (imx6_pcie->phy) {
> > > > +		ret = phy_init(imx6_pcie->phy);
> > > > +		if (ret) {
> > > > +			dev_err(dev, "waiting for phy ready
> > > > timeout!\n");
> > > > +			goto err_clk_disable;
> > > > +		}
> > > > +	}
> > >
> > > Wouldn't it be more logical to put this into imx6_pcie_init_phy()?
> > >
> > Before adding i.MX8MM PCIe support, the imx6_pcie_init_phy() only
> > touches the
> >  GPR registers. PCIe clocks and so on are not required in this case.
> > But phy_init() used by i.MX8MM PCIe touches not only the GPR registers
> > but
> >  also the PHY's registers.
> > The clocks should be on and resets of PHY should be configured
> > properly when
> >  phy_init() is invoked.
> > So, phy_init() is placed behind of imx6_pcie_deassert_core_reset()
> > here.
> 
> The PHY driver should be self-contained enough to not care about the state of
> the controller here, no? It should set all the necessary GPRs and enable clocks
> as needed on its own. Is this not the case with the current code?
> 
> Also PHY init should be called before PHY power-on, to make things symmetric
> with the shutdown paths which do phy_power_off() first, then phy_exit().
> 
Thanks for your comments.
Yes, agree with that PHY driver should be self-contained enough.
I mis-understood the sequence of phy_init() and phy_power_on() when I add
 the PHY driver. The phy_init() is relied on the phy_power_on() here.
So, I have to place the phy_init() behind phy_power_on() currently.
I think the phy_init() can be placed in imx6_pcie_init_phy() when the order
 issue is fixed.

BTW, Bjorn had noticed me this issue too [1]. Since it's a bug, I would issue
 another standalone bug fix commits to resolve this issue later.
[1] https://patchwork.ozlabs.org/project/linux-pci/patch/1655461874-16908-11-git-send-email-hongxing.zhu@nxp.com/

Best Regards
Richard Zhu

> Regards,
> Lucas