linux-kernel - RE: [RESEND v2 4/5] PCI: imx6: Fix the clock reference handling unbalance when link never came up

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Date:   Wed, 27 Oct 2021 01:29:23 +0000
From:   Richard Zhu <hongxing.zhu@....com>
To:     Bjorn Helgaas <helgaas@...nel.org>
CC:     "l.stach@...gutronix.de" <l.stach@...gutronix.de>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        "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>
Subject: RE: [RESEND v2 4/5] PCI: imx6: Fix the clock reference handling
 unbalance when link never came up

> -----Original Message-----
> From: Bjorn Helgaas <helgaas@...nel.org>
> Sent: Wednesday, October 27, 2021 12:39 AM
> To: Richard Zhu <hongxing.zhu@....com>
> Cc: l.stach@...gutronix.de; bhelgaas@...gle.com;
> lorenzo.pieralisi@....com; linux-pci@...r.kernel.org; dl-linux-imx
> <linux-imx@....com>; linux-arm-kernel@...ts.infradead.org;
> linux-kernel@...r.kernel.org; kernel@...gutronix.de
> Subject: Re: [RESEND v2 4/5] PCI: imx6: Fix the clock reference handling
> unbalance when link never came up
> 
> On Fri, Oct 22, 2021 at 08:02:17AM +0000, Richard Zhu wrote:
> > <snipped ...>
> > > >
> > > > > > -static void imx6_pcie_clk_disable(struct imx6_pcie *imx6_pcie) -{
> > > > > > -	clk_disable_unprepare(imx6_pcie->pcie);
> > > > > > -	clk_disable_unprepare(imx6_pcie->pcie_phy);
> > > > > > -	clk_disable_unprepare(imx6_pcie->pcie_bus);
> > > > > > -
> > > > > > -	switch (imx6_pcie->drvdata->variant) {
> > > > > > -	case IMX6SX:
> > > > > > -		clk_disable_unprepare(imx6_pcie->pcie_inbound_axi);
> > > > > > -		break;
> > > > > > -	case IMX7D:
> > > > > > -		regmap_update_bits(imx6_pcie->iomuxc_gpr,
> > > IOMUXC_GPR12,
> > > > > > -				   IMX7D_GPR12_PCIE_PHY_REFCLK_SEL,
> > > > > > -				   IMX7D_GPR12_PCIE_PHY_REFCLK_SEL);
> > > > > > -		break;
> > > > > > -	case IMX8MQ:
> > > > > > -		clk_disable_unprepare(imx6_pcie->pcie_aux);
> > > > > > -		break;
> > > > > > -	default:
> > > > > > -		break;
> > > >
> > > > While you're at it, this "default: break;" thing is pointless.
> > > > Normally it's better to just *move* something without changing it
> > > > at all, but this is such a simple thing I think you could drop
> > > > this at the same time as the move.
> > > >
> > > [Richard Zhu] Okay, got that. Would remove the "default:break" later.
> Thanks.
> > [Richard Zhu] I figure out that the default:break is required by
> > IMX6Q/IMX6QP.  So I just don't drop them in v3 patch-set.
> 
> That makes no sense.  The code is:
> 
>   +static void imx6_pcie_clk_disable(struct imx6_pcie *imx6_pcie)
>   +{
>   +       clk_disable_unprepare(imx6_pcie->pcie);
>   +       clk_disable_unprepare(imx6_pcie->pcie_phy);
>   +       clk_disable_unprepare(imx6_pcie->pcie_bus);
>   +
>   +       switch (imx6_pcie->drvdata->variant) {
>   +       case IMX6SX:
>   +               clk_disable_unprepare(imx6_pcie->pcie_inbound_axi);
>   +               break;
>   +       case IMX7D:
>   +               regmap_update_bits(imx6_pcie->iomuxc_gpr,
> IOMUXC_GPR12,
>   +
> IMX7D_GPR12_PCIE_PHY_REFCLK_SEL,
>   +
> IMX7D_GPR12_PCIE_PHY_REFCLK_SEL);
>   +               break;
>   +       case IMX8MQ:
>   +               clk_disable_unprepare(imx6_pcie->pcie_aux);
>   +               break;
>   +       default:
>   +               break;
>   +       }
>   +}
> 
> Why do you think it makes a difference to remove the
> "default: break;"?  There is no executable code after it.
> I don't see how IMX6Q/IMX6QP could depend on the default case.
> 
> BTW, I feel like a broken record, but your v3 posting still has inconsistent
> subject line capitalization:
> 
>   PCI: imx6: move the clock disable function to a proper place
>   PCI: dwc: add a new callback host exit function into host ops
> 
> It would be nice if they were consistent and contained more specific
> information, e.g.,
> 
>   PCI: imx6: Move imx6_pcie_clk_disable() earlier
>   PCI: dwc: Add dw_pcie_host_ops.host_exit() callback
[Richard Zhu] Got that, would change to be consistent and more specific information. Thanks a lot.

BR
Richard
> 
> Bjorn