PCI: tegra: Fix host link initialization

Commit b9ac0f9 ("PCI: dwc: Move dw_pcie_setup_rc() to DWC common
code") broke enumeration of downstream devices on Tegra:

In non-working case (next-20201211):

  0001:00:00.0 PCI bridge: NVIDIA Corporation Device 1ad2 (rev a1)
  0001:01:00.0 SATA controller: Marvell Technology Group Ltd. Device 9171 (rev 13)
  0005:00:00.0 PCI bridge: NVIDIA Corporation Device 1ad0 (rev a1)

In working case (v5.10-rc7):

  0001:00:00.0 PCI bridge: Molex Incorporated Device 1ad2 (rev a1)
  0001:01:00.0 SATA controller: Marvell Technology Group Ltd. Device 9171 (rev 13)
  0005:00:00.0 PCI bridge: Molex Incorporated Device 1ad0 (rev a1)
  0005:01:00.0 PCI bridge: PLX Technology, Inc. Device 3380 (rev ab)
  0005:02:02.0 PCI bridge: PLX Technology, Inc. Device 3380 (rev ab)
  0005:03:00.0 USB controller: PLX Technology, Inc. Device 3380 (rev ab)

The problem seems to be dw_pcie_setup_rc() is now called twice before and
after the link up handling. The fix is to move Tegra's link up handling to
.start_link() function like other DWC drivers. Tegra is a bit more
complicated than others as it re-inits the whole DWC controller to retry
the link. With this, the initialization ordering is restored to match the
prior sequence.

Fixes: b9ac0f9 ("PCI: dwc: Move dw_pcie_setup_rc() to DWC common code")
Link: https://lore.kernel.org/r/[email protected]
Reported-by: Mian Yousaf Kaukab <[email protected]>
Tested-by: Mian Yousaf Kaukab <[email protected]>
Signed-off-by: Rob Herring <[email protected]>
Signed-off-by: Bjorn Helgaas <[email protected]>
Cc: Lorenzo Pieralisi <[email protected]>
Cc: Thierry Reding <[email protected]>
Cc: Jonathan Hunter <[email protected]>
Cc: Vidya Sagar <[email protected]>

drivers/pci/controller/dwc/pcie-tegra194.c

@@ -853,12 +853,14 @@ static void config_gen3_gen4_eq_presets(struct tegra_pcie_dw *pcie)
 	dw_pcie_writel_dbi(pci, GEN3_RELATED_OFF, val);
 }
 
-static void tegra_pcie_prepare_host(struct pcie_port *pp)
+static int tegra_pcie_dw_host_init(struct pcie_port *pp)
 {
 	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
 	struct tegra_pcie_dw *pcie = to_tegra_pcie(pci);
 	u32 val;
 
+	pp->bridge->ops = &tegra_pci_ops;
+
 	if (!pcie->pcie_cap_base)
 		pcie->pcie_cap_base = dw_pcie_find_capability(&pcie->pci,
 							      PCI_CAP_ID_EXP);
@@ -907,10 +909,24 @@ static void tegra_pcie_prepare_host(struct pcie_port *pp)
 		dw_pcie_writel_dbi(pci, CFG_TIMER_CTRL_MAX_FUNC_NUM_OFF, val);
 	}
 
-	dw_pcie_setup_rc(pp);
-
 	clk_set_rate(pcie->core_clk, GEN4_CORE_CLK_FREQ);
 
+	return 0;
+}
+
+static int tegra_pcie_dw_start_link(struct dw_pcie *pci)
+{
+	u32 val, offset, speed, tmp;
+	struct tegra_pcie_dw *pcie = to_tegra_pcie(pci);
+	struct pcie_port *pp = &pci->pp;
+	bool retry = true;
+
+	if (pcie->mode == DW_PCIE_EP_TYPE) {
+		enable_irq(pcie->pex_rst_irq);
+		return 0;
+	}
+
+retry_link:
 	/* Assert RST */
 	val = appl_readl(pcie, APPL_PINMUX);
 	val &= ~APPL_PINMUX_PEX_RST;
@@ -929,19 +945,10 @@ static void tegra_pcie_prepare_host(struct pcie_port *pp)
 	appl_writel(pcie, val, APPL_PINMUX);
 
 	msleep(100);
-}
-
-static int tegra_pcie_dw_host_init(struct pcie_port *pp)
-{
-	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
-	struct tegra_pcie_dw *pcie = to_tegra_pcie(pci);
-	u32 val, tmp, offset, speed;
-
-	pp->bridge->ops = &tegra_pci_ops;
-
-	tegra_pcie_prepare_host(pp);
 
 	if (dw_pcie_wait_for_link(pci)) {
+		if (!retry)
+			return 0;
 		/*
 		 * There are some endpoints which can't get the link up if
 		 * root port has Data Link Feature (DLF) enabled.
@@ -975,10 +982,11 @@ static int tegra_pcie_dw_host_init(struct pcie_port *pp)
 		val &= ~PCI_DLF_EXCHANGE_ENABLE;
 		dw_pcie_writel_dbi(pci, offset, val);
 
-		tegra_pcie_prepare_host(pp);
+		tegra_pcie_dw_host_init(pp);
+		dw_pcie_setup_rc(pp);
 
-		if (dw_pcie_wait_for_link(pci))
-			return 0;
+		retry = false;
+		goto retry_link;
 	}
 
 	speed = dw_pcie_readw_dbi(pci, pcie->pcie_cap_base + PCI_EXP_LNKSTA) &
@@ -998,15 +1006,6 @@ static int tegra_pcie_dw_link_up(struct dw_pcie *pci)
 	return !!(val & PCI_EXP_LNKSTA_DLLLA);
 }
 
-static int tegra_pcie_dw_start_link(struct dw_pcie *pci)
-{
-	struct tegra_pcie_dw *pcie = to_tegra_pcie(pci);
-
-	enable_irq(pcie->pex_rst_irq);
-
-	return 0;
-}
-
 static void tegra_pcie_dw_stop_link(struct dw_pcie *pci)
 {
 	struct tegra_pcie_dw *pcie = to_tegra_pcie(pci);
@@ -2215,6 +2214,10 @@ static int tegra_pcie_dw_resume_noirq(struct device *dev)
 		goto fail_host_init;
 	}
 
+	ret = tegra_pcie_dw_start_link(&pcie->pci);
+	if (ret < 0)
+		goto fail_host_init;
+
 	/* Restore MSI interrupt vector */
 	dw_pcie_writel_dbi(&pcie->pci, PORT_LOGIC_MSI_CTRL_INT_0_EN,
 			   pcie->msi_ctrl_int);