From 460f382c278fe66059a773c41cbcd0db86d53983 Mon Sep 17 00:00:00 2001
From: Mathias Kresin <dev@kresin.me>
Date: Thu, 13 Apr 2017 09:47:42 +0200
Subject: [PATCH] MIPS: pci-ar724x: get PCIe controller out of reset

The ar724x pci driver expects the PCIe controller to be brought out of
reset by the bootloader.

At least the AVM Fritz 300E bootloader doesn't take care of releasing
the different PCIe controller related resets which causes an endless
hang as soon as either the PCIE Reset register (0x180f0018) or the PCI
Application Control register (0x180f0000) is read from.

Do the full "PCIE Root Complex Initialization Sequence" if the PCIe
host controller is still in reset during probing.

The QCA u-boot sleeps 10ms after the PCIE Application Control bit is
set to ready. It has been shown that 10ms might not be enough time if
PCIe should be used right after setting the bit. During my tests it
took up to 20ms till the link was up. Giving the link up to 100ms
should work for all cases.

Signed-off-by: Mathias Kresin <dev@kresin.me>
---
 arch/mips/include/asm/mach-ath79/ar71xx_regs.h |  3 ++
 arch/mips/pci/pci-ar724x.c                     | 42 ++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

--- a/arch/mips/include/asm/mach-ath79/ar71xx_regs.h
+++ b/arch/mips/include/asm/mach-ath79/ar71xx_regs.h
@@ -169,6 +169,9 @@
 #define AR724X_PLL_REG_CPU_CONFIG	0x00
 #define AR724X_PLL_REG_PCIE_CONFIG	0x10
 
+#define AR724X_PLL_REG_PCIE_CONFIG_PPL_BYPASS	BIT(16)
+#define AR724X_PLL_REG_PCIE_CONFIG_PPL_RESET	BIT(25)
+
 #define AR724X_PLL_FB_SHIFT		0
 #define AR724X_PLL_FB_MASK		0x3ff
 #define AR724X_PLL_REF_DIV_SHIFT	10
--- a/arch/mips/pci/pci-ar724x.c
+++ b/arch/mips/pci/pci-ar724x.c
@@ -12,14 +12,18 @@
 #include <linux/irq.h>
 #include <linux/pci.h>
 #include <linux/init.h>
+#include <linux/delay.h>
 #include <linux/platform_device.h>
 #include <asm/mach-ath79/ath79.h>
 #include <asm/mach-ath79/ar71xx_regs.h>
 
+#define AR724X_PCI_REG_APP		0x0
 #define AR724X_PCI_REG_RESET		0x18
 #define AR724X_PCI_REG_INT_STATUS	0x4c
 #define AR724X_PCI_REG_INT_MASK		0x50
 
+#define AR724X_PCI_APP_LTSSM_ENABLE	BIT(0)
+
 #define AR724X_PCI_RESET_LINK_UP	BIT(0)
 
 #define AR724X_PCI_INT_DEV0		BIT(14)
@@ -325,6 +329,37 @@ static void ar724x_pci_irq_init(struct a
 					 apc);
 }
 
+static void ar724x_pci_hw_init(struct ar724x_pci_controller *apc)
+{
+	u32 ppl, app;
+	int wait = 0;
+
+	/* deassert PCIe host controller and PCIe PHY reset */
+	ath79_device_reset_clear(AR724X_RESET_PCIE);
+	ath79_device_reset_clear(AR724X_RESET_PCIE_PHY);
+
+	/* remove the reset of the PCIE PLL */
+	ppl = ath79_pll_rr(AR724X_PLL_REG_PCIE_CONFIG);
+	ppl &= ~AR724X_PLL_REG_PCIE_CONFIG_PPL_RESET;
+	ath79_pll_wr(AR724X_PLL_REG_PCIE_CONFIG, ppl);
+
+	/* deassert bypass for the PCIE PLL */
+	ppl = ath79_pll_rr(AR724X_PLL_REG_PCIE_CONFIG);
+	ppl &= ~AR724X_PLL_REG_PCIE_CONFIG_PPL_BYPASS;
+	ath79_pll_wr(AR724X_PLL_REG_PCIE_CONFIG, ppl);
+
+	/* set PCIE Application Control to ready */
+	app = __raw_readl(apc->ctrl_base + AR724X_PCI_REG_APP);
+	app |= AR724X_PCI_APP_LTSSM_ENABLE;
+	__raw_writel(app, apc->ctrl_base + AR724X_PCI_REG_APP);
+
+	/* wait up to 100ms for PHY link up */
+	do {
+		mdelay(10);
+		wait++;
+	} while (wait < 10 && !ar724x_pci_check_link(apc));
+}
+
 static int ar724x_pci_probe(struct platform_device *pdev)
 {
 	struct ar724x_pci_controller *apc;
@@ -383,6 +418,13 @@ static int ar724x_pci_probe(struct platf
 	apc->pci_controller.io_resource = &apc->io_res;
 	apc->pci_controller.mem_resource = &apc->mem_res;
 
+	/*
+	 * Do the full PCIE Root Complex Initialization Sequence if the PCIe
+	 * host controller is in reset.
+	 */
+	if (ath79_reset_rr(AR724X_RESET_REG_RESET_MODULE) & AR724X_RESET_PCIE)
+		ar724x_pci_hw_init(apc);
+
 	apc->link_up = ar724x_pci_check_link(apc);
 	if (!apc->link_up)
 		dev_warn(&pdev->dev, "PCIe link is down\n");
