linux-kernel - Re: [PATCH v9 6/8] PCI: imx6: Disable clocks and regulators after link is down

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Message-ID: <5be4f4322e00e33fa9417280b0d74ecb7aab913e.camel@pengutronix.de>
Date:   Wed, 08 Jun 2022 09:35:14 +0200
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Richard Zhu <hongxing.zhu@....com>, bhelgaas@...gle.com,
        robh+dt@...nel.org, broonie@...nel.org, lorenzo.pieralisi@....com,
        jingoohan1@...il.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,
        linux-imx@....com
Subject: Re: [PATCH v9 6/8] PCI: imx6: Disable clocks and regulators after
 link is down

Am Freitag, dem 06.05.2022 um 09:47 +0800 schrieb Richard Zhu:
> Since i.MX PCIe doesn't support hot-plug, reduce power consumption
> as much as possible by disabling clocks and regulators and returning
> error when the link is down.
> 
> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 3ce3993d5797..d122c12193a6 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -845,7 +845,9 @@ static int imx6_pcie_start_link(struct dw_pcie *pci)
>  	/* Start LTSSM. */
>  	imx6_pcie_ltssm_enable(dev);
>  
> -	dw_pcie_wait_for_link(pci);
> +	ret = dw_pcie_wait_for_link(pci);
> +	if (ret)
> +		goto err_out;

This adds back error handling that has been intentionally removed in
f81f095e8771 ("PCI: imx6: Allow to probe when dw_pcie_wait_for_link()
fails"). While I agree that disabling the clocks and regulators is the
right thing to do when we don't manage to get a link, we should still
allow the driver to probe, so please add a "ret = 0" to this newly
added non-fatal error paths.

>  
>  	if (pci->link_gen == 2) {
>  		/* Allow Gen2 mode after the link is up. */
> @@ -876,12 +878,14 @@ static int imx6_pcie_start_link(struct dw_pcie *pci)
>  			ret = imx6_pcie_wait_for_speed_change(imx6_pcie);
>  			if (ret) {
>  				dev_err(dev, "Failed to bring link up!\n");
> -				goto err_reset_phy;
> +				goto err_out;
>  			}
>  		}
>  
>  		/* Make sure link training is finished as well! */
> -		dw_pcie_wait_for_link(pci);
> +		ret = dw_pcie_wait_for_link(pci);
> +		if (ret)
> +			goto err_out;
>  	} else {
>  		dev_info(dev, "Link: Gen2 disabled\n");
>  	}
> @@ -890,11 +894,18 @@ static int imx6_pcie_start_link(struct dw_pcie *pci)
>  	dev_info(dev, "Link up, Gen%i\n", tmp & PCI_EXP_LNKSTA_CLS);
>  	return 0;
>  
> -err_reset_phy:
> +err_out:
>  	dev_dbg(dev, "PHY DEBUG_R0=0x%08x DEBUG_R1=0x%08x\n",
>  		dw_pcie_readl_dbi(pci, PCIE_PORT_DEBUG0),
>  		dw_pcie_readl_dbi(pci, PCIE_PORT_DEBUG1));
>  	imx6_pcie_reset_phy(imx6_pcie);
> +	imx6_pcie_clk_disable(imx6_pcie);
> +	if (imx6_pcie->phy != NULL) {

Please use the more common if (imx6_pcie->phy) here.

Regards,
Lucas

> +		phy_power_off(imx6_pcie->phy);
> +		phy_exit(imx6_pcie->phy);
> +	}
> +	if (imx6_pcie->vpcie)
> +		regulator_disable(imx6_pcie->vpcie);
>  	return ret;
>  }
>