mux: apple DP xbar: Add Apple silicon DisplayPort crossbar

This drivers adds support for the display crossbar used to route
display controller streams to the three different modes
(DP AltMode, USB4 Tunnel #0/#1) of the Type-C ports.

Signed-off-by: Sven Peter <sven@svenpeter.dev>
(cherry picked from commit 865f23f https://github.com/AsahiLinux/linux)
Signed-off-by: John Cabaj <john.cabaj@canonical.com>

Author: svenpeter42

drivers/mux/Kconfig

@@ -31,6 +31,19 @@ config MUX_ADGS1408
 	  To compile the driver as a module, choose M here: the module will
 	  be called mux-adgs1408.
 
+config MUX_APPLE_DPXBAR
+	tristate "Apple Silicon Display Crossbar"
+	depends on ARCH_APPLE
+	help
+	  Apple Silicon Display Crossbar multiplexer.
+
+	  This drivers adds support for the display crossbar used to route
+	  display controller streams to the three different modes
+	  (DP AltMode, USB4 Tunnel #0/#1) of the Type-C ports.
+
+	  To compile this driver as a module, chose M here: the module will be
+	  called mux-apple-display-crossbar.
+
 config MUX_GPIO
 	tristate "GPIO-controlled Multiplexer"
 	depends on GPIOLIB || COMPILE_TEST

drivers/mux/Makefile

@@ -8,9 +8,11 @@ mux-adg792a-objs		:= adg792a.o
 mux-adgs1408-objs		:= adgs1408.o
 mux-gpio-objs			:= gpio.o
 mux-mmio-objs			:= mmio.o
+mux-apple-display-crossbar-objs	:= apple-display-crossbar.o
 
 obj-$(CONFIG_MULTIPLEXER)	+= mux-core.o
 obj-$(CONFIG_MUX_ADG792A)	+= mux-adg792a.o
 obj-$(CONFIG_MUX_ADGS1408)	+= mux-adgs1408.o
+obj-$(CONFIG_MUX_APPLE_DPXBAR)	+= mux-apple-display-crossbar.o
 obj-$(CONFIG_MUX_GPIO)		+= mux-gpio.o
 obj-$(CONFIG_MUX_MMIO)		+= mux-mmio.o

drivers/mux/apple-display-crossbar.c

@@ -0,0 +1,305 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Apple Silicon Display Crossbar multiplexer driver
+ *
+ * Copyright (C) Asahi Linux Contributors
+ *
+ * Author: Sven Peter <sven@svenpeter.dev>
+ */
+
+#include <linux/bitmap.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/mux/driver.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+
+#define FIFO_WR_DPTX_CLK_EN 0x000
+#define FIFO_WR_N_CLK_EN 0x004
+#define FIFO_WR_UNK_EN 0x008
+#define FIFO_RD_PCLK1_EN 0x020
+#define FIFO_RD_PCLK2_EN 0x024
+#define FIFO_RD_N_CLK_EN 0x028
+#define FIFO_RD_UNK_EN 0x02c
+
+#define OUT_PCLK1_EN 0x040
+#define OUT_PCLK2_EN 0x044
+#define OUT_N_CLK_EN 0x048
+#define OUT_UNK_EN 0x04c
+
+#define CROSSBAR_DISPEXT_EN 0x050
+#define CROSSBAR_MUX_CTRL 0x060
+#define CROSSBAR_MUX_CTRL_DPPHY_SELECT0 GENMASK(23, 20)
+#define CROSSBAR_MUX_CTRL_DPIN1_SELECT0 GENMASK(19, 16)
+#define CROSSBAR_MUX_CTRL_DPIN0_SELECT0 GENMASK(15, 12)
+#define CROSSBAR_MUX_CTRL_DPPHY_SELECT1 GENMASK(11, 8)
+#define CROSSBAR_MUX_CTRL_DPIN1_SELECT1 GENMASK(7, 4)
+#define CROSSBAR_MUX_CTRL_DPIN0_SELECT1 GENMASK(3, 0)
+#define CROSSBAR_ATC_EN 0x070
+
+#define FIFO_WR_DPTX_CLK_EN_STAT 0x800
+#define FIFO_WR_N_CLK_EN_STAT 0x804
+#define FIFO_RD_PCLK1_EN_STAT 0x820
+#define FIFO_RD_PCLK2_EN_STAT 0x824
+#define FIFO_RD_N_CLK_EN_STAT 0x828
+
+#define OUT_PCLK1_EN_STAT 0x840
+#define OUT_PCLK2_EN_STAT 0x844
+#define OUT_N_CLK_EN_STAT 0x848
+
+#define UNK_TUNABLE 0xc00
+
+#define ATC_DPIN0 BIT(0)
+#define ATC_DPIN1 BIT(4)
+#define ATC_DPPHY BIT(8)
+
+enum { MUX_DPPHY = 0, MUX_DPIN0 = 1, MUX_DPIN1 = 2, MUX_MAX = 3 };
+static const char *apple_dpxbar_names[MUX_MAX] = { "dpphy", "dpin0", "dpin1" };
+
+struct apple_dpxbar_hw {
+	unsigned int n_ufp;
+	u32 tunable;
+};
+
+struct apple_dpxbar {
+	struct device *dev;
+	void __iomem *regs;
+	int selected_dispext[MUX_MAX];
+	spinlock_t lock;
+};
+
+static inline void dpxbar_mask32(struct apple_dpxbar *xbar, u32 reg, u32 mask,
+				 u32 set)
+{
+	u32 value = readl(xbar->regs + reg);
+	value &= ~mask;
+	value |= set;
+	writel(value, xbar->regs + reg);
+}
+
+static inline void dpxbar_set32(struct apple_dpxbar *xbar, u32 reg, u32 set)
+{
+	dpxbar_mask32(xbar, reg, 0, set);
+}
+
+static inline void dpxbar_clear32(struct apple_dpxbar *xbar, u32 reg, u32 clear)
+{
+	dpxbar_mask32(xbar, reg, clear, 0);
+}
+
+static int apple_dpxbar_set(struct mux_control *mux, int state)
+{
+	struct apple_dpxbar *dpxbar = mux_chip_priv(mux->chip);
+	unsigned int index = mux_control_get_index(mux);
+	unsigned long flags;
+	unsigned int mux_state;
+	unsigned int dispext_bit;
+	unsigned int atc_bit;
+	bool enable;
+	int ret = 0;
+	u32 mux_mask, mux_set;
+
+	if (state == MUX_IDLE_DISCONNECT) {
+		/*
+		 * Technically this will select dispext0,0 in the mux control
+		 * register. Practically that doesn't matter since everything
+		 * else is disabled.
+		 */
+		mux_state = 0;
+		enable = false;
+	} else if (state >= 0 && state < 9) {
+		dispext_bit = 1 << state;
+		mux_state = state;
+		enable = true;
+	} else {
+		return -EINVAL;
+	}
+
+	switch (index) {
+	case MUX_DPPHY:
+		mux_mask = CROSSBAR_MUX_CTRL_DPPHY_SELECT0 |
+			   CROSSBAR_MUX_CTRL_DPPHY_SELECT1;
+		mux_set =
+			FIELD_PREP(CROSSBAR_MUX_CTRL_DPPHY_SELECT0, mux_state) |
+			FIELD_PREP(CROSSBAR_MUX_CTRL_DPPHY_SELECT1, mux_state);
+		atc_bit = ATC_DPPHY;
+		break;
+	case MUX_DPIN0:
+		mux_mask = CROSSBAR_MUX_CTRL_DPIN0_SELECT0 |
+			   CROSSBAR_MUX_CTRL_DPIN0_SELECT1;
+		mux_set =
+			FIELD_PREP(CROSSBAR_MUX_CTRL_DPIN0_SELECT0, mux_state) |
+			FIELD_PREP(CROSSBAR_MUX_CTRL_DPIN0_SELECT1, mux_state);
+		atc_bit = ATC_DPIN0;
+		break;
+	case MUX_DPIN1:
+		mux_mask = CROSSBAR_MUX_CTRL_DPIN1_SELECT0 |
+			   CROSSBAR_MUX_CTRL_DPIN1_SELECT1;
+		mux_set =
+			FIELD_PREP(CROSSBAR_MUX_CTRL_DPIN1_SELECT0, mux_state) |
+			FIELD_PREP(CROSSBAR_MUX_CTRL_DPIN1_SELECT1, mux_state);
+		atc_bit = ATC_DPIN1;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	spin_lock_irqsave(&dpxbar->lock, flags);
+
+	/* ensure the selected dispext isn't already used in this crossbar */
+	if (enable) {
+		for (int i = 0; i < MUX_MAX; ++i) {
+			if (i == index)
+				continue;
+			if (dpxbar->selected_dispext[i] == state) {
+				spin_unlock_irqrestore(&dpxbar->lock, flags);
+				return -EBUSY;
+			}
+		}
+	}
+
+	dpxbar_set32(dpxbar, OUT_N_CLK_EN, atc_bit);
+	dpxbar_clear32(dpxbar, OUT_UNK_EN, atc_bit);
+	dpxbar_clear32(dpxbar, OUT_PCLK1_EN, atc_bit);
+	dpxbar_clear32(dpxbar, CROSSBAR_ATC_EN, atc_bit);
+
+	if (dpxbar->selected_dispext[index] >= 0) {
+		u32 prev_dispext_bit = 1 << dpxbar->selected_dispext[index];
+
+		dpxbar_set32(dpxbar, FIFO_WR_N_CLK_EN, prev_dispext_bit);
+		dpxbar_set32(dpxbar, FIFO_RD_N_CLK_EN, prev_dispext_bit);
+		dpxbar_clear32(dpxbar, FIFO_WR_UNK_EN, prev_dispext_bit);
+		dpxbar_clear32(dpxbar, FIFO_RD_UNK_EN, prev_dispext_bit);
+		dpxbar_clear32(dpxbar, FIFO_WR_DPTX_CLK_EN, prev_dispext_bit);
+		dpxbar_clear32(dpxbar, FIFO_RD_PCLK1_EN, prev_dispext_bit);
+		dpxbar_clear32(dpxbar, CROSSBAR_DISPEXT_EN, prev_dispext_bit);
+
+		dpxbar->selected_dispext[index] = -1;
+	}
+
+	dpxbar_mask32(dpxbar, CROSSBAR_MUX_CTRL, mux_mask, mux_set);
+
+	if (enable) {
+		dpxbar_clear32(dpxbar, FIFO_WR_N_CLK_EN, dispext_bit);
+		dpxbar_clear32(dpxbar, FIFO_RD_N_CLK_EN, dispext_bit);
+		dpxbar_clear32(dpxbar, OUT_N_CLK_EN, atc_bit);
+		dpxbar_set32(dpxbar, FIFO_WR_UNK_EN, dispext_bit);
+		dpxbar_set32(dpxbar, FIFO_RD_UNK_EN, dispext_bit);
+		dpxbar_set32(dpxbar, OUT_UNK_EN, atc_bit);
+		dpxbar_set32(dpxbar, FIFO_WR_DPTX_CLK_EN, dispext_bit);
+		dpxbar_set32(dpxbar, FIFO_RD_PCLK1_EN, dispext_bit);
+		dpxbar_set32(dpxbar, OUT_PCLK1_EN, atc_bit);
+		dpxbar_set32(dpxbar, CROSSBAR_ATC_EN, atc_bit);
+		dpxbar_set32(dpxbar, CROSSBAR_DISPEXT_EN, dispext_bit);
+
+		/*
+		 * Work around some HW quirk:
+		 * Without toggling the RD_PCLK enable here the connection
+		 * doesn't come up. Testing has shown that a delay of about
+		 * 5 usec is required which is doubled here to be on the
+		 * safe side.
+		 */
+		dpxbar_clear32(dpxbar, FIFO_RD_PCLK1_EN, dispext_bit);
+		udelay(10);
+		dpxbar_set32(dpxbar, FIFO_RD_PCLK1_EN, dispext_bit);
+
+		dpxbar->selected_dispext[index] = state;
+	}
+
+	spin_unlock_irqrestore(&dpxbar->lock, flags);
+
+	if (enable)
+		dev_info(dpxbar->dev, "Switched %s to dispext%u,%u\n",
+			 apple_dpxbar_names[index], mux_state >> 1,
+			 mux_state & 1);
+	else
+		dev_info(dpxbar->dev, "Switched %s to disconnected state\n",
+			 apple_dpxbar_names[index]);
+
+	return ret;
+}
+
+static const struct mux_control_ops apple_dpxbar_ops = {
+	.set = apple_dpxbar_set,
+};
+
+static int apple_dpxbar_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct mux_chip *mux_chip;
+	struct apple_dpxbar *dpxbar;
+	const struct apple_dpxbar_hw *hw;
+	int ret;
+
+	hw = of_device_get_match_data(dev);
+	mux_chip = devm_mux_chip_alloc(dev, MUX_MAX, sizeof(*dpxbar));
+	if (IS_ERR(mux_chip))
+		return PTR_ERR(mux_chip);
+
+	dpxbar = mux_chip_priv(mux_chip);
+	mux_chip->ops = &apple_dpxbar_ops;
+	spin_lock_init(&dpxbar->lock);
+
+	dpxbar->dev = dev;
+	dpxbar->regs = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(dpxbar->regs))
+		return PTR_ERR(dpxbar->regs);
+
+	writel(hw->tunable, dpxbar->regs + UNK_TUNABLE);
+
+	for (unsigned int i = 0; i < MUX_MAX; ++i) {
+		mux_chip->mux[i].states = hw->n_ufp;
+		mux_chip->mux[i].idle_state = MUX_IDLE_DISCONNECT;
+		dpxbar->selected_dispext[i] = -1;
+	}
+
+	ret = devm_mux_chip_register(dev, mux_chip);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+const static struct apple_dpxbar_hw apple_dpxbar_hw_t8103 = {
+	.n_ufp = 2,
+	.tunable = 0,
+};
+
+const static struct apple_dpxbar_hw apple_dpxbar_hw_t6000 = {
+	.n_ufp = 9,
+	.tunable = 5,
+};
+
+static const struct of_device_id apple_dpxbar_ids[] = {
+	{
+		.compatible = "apple,t8103-display-crossbar",
+		.data = &apple_dpxbar_hw_t8103,
+	},
+	{
+		.compatible = "apple,t8112-display-crossbar",
+		.data = &apple_dpxbar_hw_t8103,
+	},
+	{
+		.compatible = "apple,t6000-display-crossbar",
+		.data = &apple_dpxbar_hw_t6000,
+	},
+	{}
+};
+MODULE_DEVICE_TABLE(of, apple_dpxbar_ids);
+
+static struct platform_driver apple_dpxbar_driver = {
+	.driver = {
+		.name = "apple-display-crossbar",
+		.of_match_table	= apple_dpxbar_ids,
+	},
+	.probe = apple_dpxbar_probe,
+};
+module_platform_driver(apple_dpxbar_driver);
+
+MODULE_DESCRIPTION("Apple Silicon display crossbar multiplexer driver");
+MODULE_AUTHOR("Sven Peter <sven@svenpeter.dev>");
+MODULE_LICENSE("GPL v2");