input: apple: Add support for Apple MTP keyboard

Apple M2 devices have an MTP coprocessor in charge of keyboard/trackpad
handling, communicating over a DockChannel interface. Add a simple
driver for this.

The keyboard does not require any initialization messages, but we have a
problem: we cannot reset the MTP so Linux can start it fresh, and it
delivers a number of informative packets on startup. To work around
this, we buffer those messages and re-inject them into the FIFO (which
is big enough to hold all of them) on shutdown, so Linux finds them when
it initializes its driver. The actual MTP coprocessor is quiesced, which
does work properly.

Signed-off-by: Hector Martin <marcan@marcan.st>

drivers/input/Kconfig

@@ -60,6 +60,15 @@ config APPLE_SPI_KEYB
 	  laptops based on Apple SoCs. These keyboards use an
 	  Apple-specific HID-over-SPI protocol.
 
+config APPLE_MTP_KEYB
+	bool "Enable Apple MTP keyboard support"
+	select APPLE_KEYB
+	depends on DM_KEYBOARD && MISC
+	help
+	  This adds a driver for the keyboards found on various
+	  laptops based on Apple M2 and newer SoCs. These keyboards use an
+	  Apple-specific HID-over-DockChannel protocol.
+
 config CROS_EC_KEYB
 	bool "Enable Chrome OS EC keyboard support"
 	depends on INPUT

drivers/input/Makefile

@@ -12,6 +12,7 @@ ifndef CONFIG_SPL_BUILD
 
 obj-$(CONFIG_APPLE_KEYB) += apple_kbd.o
 obj-$(CONFIG_APPLE_SPI_KEYB) += apple_spi_kbd.o
+obj-$(CONFIG_APPLE_MTP_KEYB) += apple_mtp_kbd.o
 obj-$(CONFIG_I8042_KEYB) += i8042.o
 obj-$(CONFIG_TEGRA_KEYBOARD) += input.o tegra-kbc.o
 obj-$(CONFIG_TWL4030_INPUT) += twl4030.o

drivers/input/apple_mtp_kbd.c

@@ -0,0 +1,262 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2021 Mark Kettenis <kettenis@openbsd.org>
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <dm/simple_bus.h>
+#include <dm/device_compat.h>
+#include <dm/device-internal.h>
+#include <mailbox.h>
+#include <keyboard.h>
+#include <stdio_dev.h>
+#include <asm/arch/rtkit.h>
+#include <asm/io.h>
+#include <linux/input.h>
+#include "apple_kbd.h"
+
+struct apple_mtp_kbd_priv {
+	struct apple_kbd_priv kbd;
+	struct udevice *helper;
+	void *local;
+	void *rmt;
+
+	u8 *init_data;
+	u32 init_size;
+	u32 fifo_size;
+};
+
+#define DATA_TX8		0x4
+#define DATA_TX_FREE		0x14
+#define DATA_RX8		0x1c
+#define DATA_RX_COUNT		0x2c
+
+struct dchid_hdr {
+	u8 hdr_len;
+	u8 channel;
+	__le16 length;
+	u8 seq;
+	u8 iface;
+	__le16 pad;
+} __packed;
+
+static int dockchannel_read(struct udevice *dev, void *buf, size_t size)
+{
+	struct apple_mtp_kbd_priv *priv = dev_get_priv(dev);
+	int ret = 0;
+	u8 b;
+	u8 *p = buf;
+
+	while (size--) {
+		ulong start;
+		start = get_timer(0);
+		while (get_timer(start) < 100) {
+			if (readl(priv->local + DATA_RX_COUNT) != 0)
+				break;
+		}
+
+		if (readl(priv->local + DATA_RX_COUNT) == 0) {
+			return -ETIME;
+		}
+
+		b = readl(priv->local + DATA_RX8) >> 8;
+		if (buf)
+			*p++ = b;
+
+		ret++;
+	}
+
+	return ret;
+}
+
+static int apple_mtp_kbd_check(struct input_config *input)
+{
+	struct udevice *dev = input->dev;
+	struct apple_mtp_kbd_priv *priv = dev_get_priv(dev);
+	struct dchid_hdr hdr;
+	int ret;
+
+	/* Poll for syslogs if RTKit is up */
+	if (priv->helper)
+		apple_rtkit_helper_poll(priv->helper, 0);
+
+	u32 pending = readl(priv->local + DATA_RX_COUNT);
+	if (pending < 8)
+		return 0;
+
+	ret = dockchannel_read(dev, &hdr, sizeof(hdr));
+	if (ret < 0) {
+		dev_err(dev, "failed to read packet header\n");
+		return ret;
+	}
+
+	/* Save comm init messages for the next stage */
+	if (hdr.iface == 0) {
+		int space = priv->fifo_size - priv->init_size;
+		int need = hdr.length + sizeof(hdr) + 4;
+
+		if (space < need) {
+			dev_err(dev, "out of buf space (%d > %d)\n",
+				need, space);
+			ret = dockchannel_read(dev, NULL, hdr.length + 4);
+			if (ret < 0)
+				return ret;
+		} else {
+			u8 *p = &priv->init_data[priv->init_size];
+
+			memcpy(p, &hdr, sizeof(hdr));
+			ret = dockchannel_read(dev, p + sizeof(hdr), hdr.length + 4);
+			if (ret < 0)
+				return ret;
+			priv->init_size += need;
+		}
+	} else if (hdr.channel == 0x12 && hdr.length == 0x14) {
+		u8 buf[0x18];
+
+		ret = dockchannel_read(dev, buf, 0x18);
+		if (ret < 0)
+			return ret;
+
+		if (!priv->helper)
+			return 1; /* Ignore if shutting down */
+
+		/* Just assume it's a keyboard report */
+		return apple_kbd_handle_report(input, &priv->kbd, buf + 8, 0xc);
+	} else {
+		printk("mtp: unknown message ch=%02x l=%04x if=%02x\n",
+		       hdr.channel, hdr.length, hdr.iface);
+		ret = dockchannel_read(dev, NULL, hdr.length + 4);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int get_rtkit_helper(struct udevice *dev)
+{
+	struct apple_mtp_kbd_priv *priv = dev_get_priv(dev);
+	int ret;
+	u32 phandle;
+	ofnode of_mtp;
+
+	ret = dev_read_u32(dev, "apple,helper-cpu", &phandle);
+	if (ret < 0)
+		return ret;
+
+	of_mtp = ofnode_get_by_phandle(phandle);
+	ret = uclass_get_device_by_ofnode(UCLASS_MISC, of_mtp, &priv->helper);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static int apple_mtp_kbd_probe(struct udevice *dev)
+{
+	struct apple_mtp_kbd_priv *priv = dev_get_priv(dev);
+	struct keyboard_priv *uc_priv = dev_get_uclass_priv(dev);
+	struct stdio_dev *sdev = &uc_priv->sdev;
+	struct input_config *input = &uc_priv->input;
+	int ret;
+	fdt_addr_t reg;
+
+	printf("mtp_kbd_probe\n");
+
+	reg = dev_read_addr_name(dev, "data");
+	if (reg == FDT_ADDR_T_NONE) {
+		dev_err(dev, "no reg property for local FIFO data registers\n");
+		return -EINVAL;
+	}
+	priv->local = (void *)reg;
+
+	reg = dev_read_addr_name(dev, "rmt-data");
+	if (reg == FDT_ADDR_T_NONE) {
+		dev_err(dev, "no reg property for remote FIFO data registers\n");
+		return -EINVAL;
+	}
+	priv->rmt = (void *)reg;
+
+	ret = dev_read_u32(dev, "apple,fifo-size", &priv->fifo_size);
+	if (ret < 0 || !priv->fifo_size) {
+		dev_err(dev, "no apple,fifo-size property\n");
+		return ret;
+	}
+
+	ret = get_rtkit_helper(dev);
+	if (ret < 0) {
+		dev_err(dev, "Failed to get helper device (%d)\n", ret);
+		return ret;
+	}
+
+	priv->init_data = malloc(priv->fifo_size);
+	if (!priv->init_data)
+		return -ENOMEM;
+
+	input->dev = dev;
+	input->read_keys = apple_mtp_kbd_check;
+	input_add_tables(input, false);
+	strcpy(sdev->name, "mtpkbd");
+
+	return input_stdio_register(sdev);
+}
+
+static int apple_mtp_kbd_remove(struct udevice *dev)
+{
+	struct apple_mtp_kbd_priv *priv = dev_get_priv(dev);
+	struct keyboard_priv *uc_priv = dev_get_uclass_priv(dev);
+	struct input_config *input = &uc_priv->input;
+	int i;
+
+	if (priv->helper) {
+		device_remove(priv->helper, DM_REMOVE_NORMAL);
+		priv->helper = NULL;
+	}
+
+	/* Drain the FIFO */
+	while (readl(priv->local + DATA_RX_COUNT)) {
+		if (apple_mtp_kbd_check(input) < 0) {
+			dev_err(dev, "Failed to drain FIFO\n");
+			break;
+		}
+	}
+
+	/* Stuff init messages back into FIFO for the next stage to find */
+	for (i = 0; i < priv->init_size; i++)
+		writel(priv->init_data[i], priv->rmt + DATA_TX8);
+
+	return 0;
+}
+
+static const struct keyboard_ops apple_mtp_kbd_ops = {
+};
+
+static const struct udevice_id apple_mtp_kbd_of_match[] = {
+	{ .compatible = "apple,dockchannel-hid" },
+	{ /* sentinel */ }
+};
+
+U_BOOT_DRIVER(apple_mtp_kbd) = {
+	.name = "apple_mtp_kbd",
+	.id = UCLASS_KEYBOARD,
+	.of_match = apple_mtp_kbd_of_match,
+	.probe = apple_mtp_kbd_probe,
+	.remove = apple_mtp_kbd_remove,
+	.priv_auto = sizeof(struct apple_mtp_kbd_priv),
+	.ops = &apple_mtp_kbd_ops,
+	.flags = DM_FLAG_OS_PREPARE,
+};
+
+/* Treat dockchannel as a simple-bus, since we don't use the IRQ stuff */
+
+static const struct udevice_id dockchannel_bus_ids[] = {
+	{ .compatible = "apple,dockchannel" },
+	{ }
+};
+
+U_BOOT_DRIVER(dockchannel) = {
+	.name	= "dockchannel",
+	.id	= UCLASS_SIMPLE_BUS,
+	.of_match = of_match_ptr(dockchannel_bus_ids),
+};

include/configs/apple.h

@@ -5,7 +5,7 @@
 
 /* Environment */
 #define ENV_DEVICE_SETTINGS \
-	"stdin=serial,usbkbd,spikbd\0" \
+	"stdin=serial,usbkbd,spikbd,mtpkbd\0" \
 	"stdout=serial,vidconsole\0" \
 	"stderr=serial,vidconsole\0"