linux-kernel - Re: [PATCH v2] PCI: imx6: Assert i.MX8MM CLKREQ# even if no device present

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Message-ID: <2e4f1fa1add244b12954970b3c02cbe503176a26.camel@pengutronix.de>
Date:   Wed, 16 Mar 2022 10:29:29 +0100
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Richard Zhu <hongxing.zhu@....com>, bhelgaas@...gle.com,
        lorenzo.pieralisi@....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 v2] PCI: imx6: Assert i.MX8MM CLKREQ# even if no device
 present

Am Donnerstag, dem 24.02.2022 um 11:06 +0800 schrieb Richard Zhu:
> The CLKREQ# signal is an open drain, active low signal that is driven
> low by the remote Endpoint device. But it might not be driven low if no
> Endpoint device is connected.
> 
> On i.MX8MM PCIe, phy_init() may fail and system boot may hang if no
> Endpoint is connected to assert CLKREQ#.
> 
> Handle this as on i.MX8MQ, where we explicitly assert CLKREQ# so the
> PHY can be initialized.
> 
> Fixes: 178e244cb6e2 ("PCI: imx: Add the imx8mm pcie support")
> Signed-off-by: Richard Zhu <hongxing.zhu@....com>

Reviewed-by: Lucas Stach <l.stach@...gutronix.de>

> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 78e32a539060..168cb1287ba9 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -447,10 +447,6 @@ static int imx6_pcie_enable_ref_clk(struct imx6_pcie *imx6_pcie)
>  	case IMX7D:
>  		break;
>  	case IMX8MM:
> -		ret = clk_prepare_enable(imx6_pcie->pcie_aux);
> -		if (ret)
> -			dev_err(dev, "unable to enable pcie_aux clock\n");
> -		break;
>  	case IMX8MQ:
>  		ret = clk_prepare_enable(imx6_pcie->pcie_aux);
>  		if (ret) {