RE: [RESEND v2 5/5] PCI: imx6: Add the compliance tests mode support

-----Original Message-----
From: Lucas Stach <l.stach@pengutronix.de>
Sent: Saturday, October 16, 2021 2:29 AM
To: Richard Zhu <hongxing.zhu@nxp.com>; bhelgaas@google.com;
lorenzo.pieralisi@arm.com
Cc: linux-pci@vger.kernel.org; dl-linux-imx <redacted>;
linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org;
kernel@pengutronix.de
Subject: Re: [RESEND v2 5/5] PCI: imx6: Add the compliance tests mode
support

Am Freitag, dem 15.10.2021 um 14:05 +0800 schrieb Richard Zhu:

quoted

Refer to the system board signal Quality of PCIe archiecture PHY test
specification. Signal quality tests(for example: jitters,
differential eye opening and so on ) can be executed with devices in
the polling.compliance state.

To let the device support polling.compliance stat, the clocks and
powers shouldn't be turned off when the probe of device driver is failed.

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@nxp.com>
---
 drivers/pci/controller/dwc/pci-imx6.c | 32
++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/drivers/pci/controller/dwc/pci-imx6.c

b/drivers/pci/controller/dwc/pci-imx6.c
index d6a5d99ffa52..e861a516d517 100644

--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c

@@ -143,6 +143,10 @@ 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; @@ -812,10 +816,12 @@ 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);

@@ -876,9 +882,12 @@ static int imx6_pcie_start_link(struct dw_pcie

*pci)

quoted

 		dw_pcie_readl_dbi(pci, PCIE_PORT_DEBUG0),
 		dw_pcie_readl_dbi(pci, PCIE_PORT_DEBUG1));
 	imx6_pcie_reset_phy(imx6_pcie);

Is it correct to reset the PHY here when in compliance test mode?

[Richard Zhu] It doesn't matter. PHY reset just let the PHY enter into a dedicated stat after link is down.
This wouldn't impact the compliance tests mode later.

Best Regards
Richard Zhu

quoted

-	imx6_pcie_clk_disable(imx6_pcie);
-	if (imx6_pcie->vpcie && regulator_is_enabled(imx6_pcie->vpcie) > 0)
-		regulator_disable(imx6_pcie->vpcie);
+	if (!imx6_pcie_cmp_mode) {
+		imx6_pcie_clk_disable(imx6_pcie);
+		if (imx6_pcie->vpcie
+		    && regulator_is_enabled(imx6_pcie->vpcie) > 0)
+			regulator_disable(imx6_pcie->vpcie);
+	}
 	return ret;
 }

@@ -1183,8 +1192,15 @@ static int imx6_pcie_probe(struct

platform_device *pdev)

quoted

 		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");

quoted

+			ret = 0;
+		} else {
+			dev_err(dev, "Unable to add pcie port.\n");
+		}
 		return ret;
+	}

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