PCI: apple: Set up reference clocks when probing

Apple's PCIe controller requires clocks to be configured in order to
bring up the hardware. Add the register pokes required to do so.

Adapted from Corellium's driver via Mark Kettenis's U-Boot patches.
Co-developed-by: Stan Skowronek <stan@corellium.com>
Link: https://lore.kernel.org/r/20210929163847.2807812-6-maz@kernel.orgSigned-off-by: Stan Skowronek <stan@corellium.com>
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/controller/pcie-apple.c

@@ -132,6 +132,48 @@ static void rmw_set(u32 set, void __iomem *addr)
 	writel_relaxed(readl_relaxed(addr) | set, addr);
 }
 
+static void rmw_clear(u32 clr, void __iomem *addr)
+{
+	writel_relaxed(readl_relaxed(addr) & ~clr, addr);
+}
+
+static int apple_pcie_setup_refclk(struct apple_pcie *pcie,
+				   struct apple_pcie_port *port)
+{
+	u32 stat;
+	int res;
+
+	res = readl_relaxed_poll_timeout(pcie->base + CORE_RC_PHYIF_STAT, stat,
+					 stat & CORE_RC_PHYIF_STAT_REFCLK,
+					 100, 50000);
+	if (res < 0)
+		return res;
+
+	rmw_set(CORE_LANE_CTL_CFGACC, pcie->base + CORE_LANE_CTL(port->idx));
+	rmw_set(CORE_LANE_CFG_REFCLK0REQ, pcie->base + CORE_LANE_CFG(port->idx));
+
+	res = readl_relaxed_poll_timeout(pcie->base + CORE_LANE_CFG(port->idx),
+					 stat, stat & CORE_LANE_CFG_REFCLK0ACK,
+					 100, 50000);
+	if (res < 0)
+		return res;
+
+	rmw_set(CORE_LANE_CFG_REFCLK1, pcie->base + CORE_LANE_CFG(port->idx));
+	res = readl_relaxed_poll_timeout(pcie->base + CORE_LANE_CFG(port->idx),
+					 stat, stat & CORE_LANE_CFG_REFCLK1,
+					 100, 50000);
+
+	if (res < 0)
+		return res;
+
+	rmw_clear(CORE_LANE_CTL_CFGACC, pcie->base + CORE_LANE_CTL(port->idx));
+
+	rmw_set(CORE_LANE_CFG_REFCLKEN, pcie->base + CORE_LANE_CFG(port->idx));
+	rmw_set(PORT_REFCLK_EN, port->base + PORT_REFCLK);
+
+	return 0;
+}
+
 static int apple_pcie_setup_port(struct apple_pcie *pcie,
 				 struct device_node *np)
 {
@@ -165,6 +207,10 @@ static int apple_pcie_setup_port(struct apple_pcie *pcie,
 
 	rmw_set(PORT_APPCLK_EN, port->base + PORT_APPCLK);
 
+	ret = apple_pcie_setup_refclk(pcie, port);
+	if (ret < 0)
+		return ret;
+
 	rmw_set(PORT_PERST_OFF, port->base + PORT_PERST);
 	gpiod_set_value(reset, 1);