linux-kernel - Re: [PATCH v9 8/8] PCI: imx6: Add compliance tests mode support

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Message-ID: <6550645c8163bad0b36eebdfceeb244f57329e9e.camel@pengutronix.de>
Date:   Wed, 08 Jun 2022 09:48:33 +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 8/8] PCI: imx6: Add compliance tests mode support

Am Freitag, dem 06.05.2022 um 09:47 +0800 schrieb Richard Zhu:
> Refer to the Chapter 3.2 System Board Signal Quality of PCI Express
> Architecture PHY Test Specification Revision 2.0.
> 
> Signal quality tests (for example: jitter, differential eye opening and
> so on) can be executed with devices in the polling.compliance state.
> 
> To let the device support polling.compliance state, the clocks and powers
> shouldn't be turned off when the probe of device driver fails.
> 
> Based on CLB (Compliance Load Board) Test Fixture and so on test
> equipments, the PHY link would be down during the compliance tests.
> Refer to this scenario, add the i.MX PCIe compliance tests mode enable
> support, and keep the clocks and powers on, and finish the driver probe
> without error return.
> 
> Use the "pci_imx6.compliance=1" in kernel command line to enable the
> compliance tests mode.
> 
> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 39 ++++++++++++++++++---------
>  1 file changed, 27 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index f0ffd9011975..f78b59822626 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -146,6 +146,10 @@ struct imx6_pcie {
>  #define PHY_RX_OVRD_IN_LO_RX_DATA_EN		BIT(5)
>  #define PHY_RX_OVRD_IN_LO_RX_PLL_EN		BIT(3)
>  
> +static bool imx6_pcie_cmp_mode;
> +module_param_named(compliance, imx6_pcie_cmp_mode, bool, 0644);
> +MODULE_PARM_DESC(compliance, "i.MX PCIe compliance test mode (1=compliance test mode enabled)");
> +
>  static int pcie_phy_poll_ack(struct imx6_pcie *imx6_pcie, bool exp_val)
>  {
>  	struct dw_pcie *pci = imx6_pcie->pci;
> @@ -826,10 +830,12 @@ static int imx6_pcie_start_link(struct dw_pcie *pci)
>  	 * started in Gen2 mode, there is a possibility the devices on the
>  	 * bus will not be detected at all.  This happens with PCIe switches.
>  	 */
> -	tmp = dw_pcie_readl_dbi(pci, offset + PCI_EXP_LNKCAP);
> -	tmp &= ~PCI_EXP_LNKCAP_SLS;
> -	tmp |= PCI_EXP_LNKCAP_SLS_2_5GB;
> -	dw_pcie_writel_dbi(pci, offset + PCI_EXP_LNKCAP, tmp);
> +	if (!imx6_pcie_cmp_mode) {
> +		tmp = dw_pcie_readl_dbi(pci, offset + PCI_EXP_LNKCAP);
> +		tmp &= ~PCI_EXP_LNKCAP_SLS;
> +		tmp |= PCI_EXP_LNKCAP_SLS_2_5GB;
> +		dw_pcie_writel_dbi(pci, offset + PCI_EXP_LNKCAP, tmp);
> +	}
>  
>  	/* Start LTSSM. */
>  	imx6_pcie_ltssm_enable(dev);
> @@ -887,14 +893,16 @@ static int imx6_pcie_start_link(struct dw_pcie *pci)
>  	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) {
> -		phy_power_off(imx6_pcie->phy);
> -		phy_exit(imx6_pcie->phy);
> +	if (!imx6_pcie_cmp_mode) {
> +		imx6_pcie_reset_phy(imx6_pcie);
> +		imx6_pcie_clk_disable(imx6_pcie);
> +		if (imx6_pcie->phy != NULL) {
> +			phy_power_off(imx6_pcie->phy);
> +			phy_exit(imx6_pcie->phy);
> +		}
> +		if (imx6_pcie->vpcie)
> +			regulator_disable(imx6_pcie->vpcie);
>  	}
> -	if (imx6_pcie->vpcie)
> -		regulator_disable(imx6_pcie->vpcie);
>  	return ret;
>  }
>  
> @@ -1289,8 +1297,15 @@ static int imx6_pcie_probe(struct platform_device *pdev)
>  		return ret;
>  
>  	ret = dw_pcie_host_init(&pci->pp);
> -	if (ret < 0)
> +	if (ret < 0) {
> +		if (imx6_pcie_cmp_mode) {
> +			dev_info(dev, "driver loaded with compliance test mode enabled\n");
> +			ret = 0;
> +		} else {
> +			dev_err(dev, "unable to add PCIe port\n");
> +		}
>  		return ret;
> +	}

If you drop the error return from imx6_pcie_start_link, like I
suggested in patch 6/8, you don't need this block as dw_pcie_host_init
will succeed even if the link is down or in compliance test mode.

Regards,
Lucas

>  
>  	if (pci_msi_enabled()) {
>  		u8 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_MSI);