linux-kernel - [PATCH v3 05/10] PCI: apple: Set up reference clocks when probing

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Date:   Mon, 13 Sep 2021 19:25:45 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Stan Skowronek <stan@...ellium.com>,
        Mark Kettenis <kettenis@...nbsd.org>,
        Sven Peter <sven@...npeter.dev>,
        Hector Martin <marcan@...can.st>,
        Robin Murphy <Robin.Murphy@....com>, kernel-team@...roid.com
Subject: [PATCH v3 05/10] PCI: apple: Set up reference clocks when probing

From: Alyssa Rosenzweig <alyssa@...enzweig.io>

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@...ellium.com>
Signed-off-by: Stan Skowronek <stan@...ellium.com>
Signed-off-by: Alyssa Rosenzweig <alyssa@...enzweig.io>
Signed-off-by: Marc Zyngier <maz@...nel.org>
Link: https://lore.kernel.org/r/20210816031621.240268-4-alyssa@rosenzweig.io
---
 drivers/pci/controller/pcie-apple.c | 44 +++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/drivers/pci/controller/pcie-apple.c b/drivers/pci/controller/pcie-apple.c
index f3c414950a10..dabbfc2e1fb0 100644
--- a/drivers/pci/controller/pcie-apple.c
+++ b/drivers/pci/controller/pcie-apple.c
@@ -132,6 +132,46 @@ static inline void rmwl(u32 clr, u32 set, void __iomem *addr)
 	writel_relaxed((readl_relaxed(addr) & ~clr) | set, 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;
+
+	rmwl(0, CORE_LANE_CTL_CFGACC, pcie->base + CORE_LANE_CTL(port->idx));
+	rmwl(0, 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;
+
+	rmwl(0, 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;
+
+	rmwl(CORE_LANE_CTL_CFGACC, 0, pcie->base + CORE_LANE_CTL(port->idx));
+
+	/* Flush writes before enabling the clocks */
+	dma_wmb();
+
+	rmwl(0, CORE_LANE_CFG_REFCLKEN, pcie->base + CORE_LANE_CFG(port->idx));
+	rmwl(0, 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 +205,10 @@ static int apple_pcie_setup_port(struct apple_pcie *pcie,
 
 	rmwl(0, PORT_APPCLK_EN, port + PORT_APPCLK);
 
+	ret = apple_pcie_setup_refclk(pcie, port);
+	if (ret < 0)
+		return ret;
+
 	rmwl(0, PORT_PERST_OFF, port->base + PORT_PERST);
 	gpiod_set_value(reset, 1);
 
-- 
2.30.2