input: apple: Add support for Apple SPI keyboard

This driver adds support for the keyboard on Apple Silicon laptops.
The controller for this keyboard sits on an SPI bus and uses an
Apple-specific HID over SPI protocol. The packets sent by this
controller for key presses and key releases are fairly simple and
are decoded directly by the code in this driver and converted into
standard Linux keycodes. The same controller handles the touchpad
found on these laptops.  Packets for touchpad events are simply
ignored.

Signed-off-by: Mark Kettenis <kettenis@openbsd.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested on: Macbook Air M1
Tested-by: Simon Glass <sjg@chromium.org>

1 files changed, 271 insertions, 0 deletions

diff --git a/drivers/input/apple_spi_kbd.c b/drivers/input/apple_spi_kbd.c
new file mode 100644
index 0000000000..7cf12f453a
--- /dev/null
+++ b/drivers/input/apple_spi_kbd.c
@@ -0,0 +1,271 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2021 Mark Kettenis <kettenis@openbsd.org>
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <keyboard.h>
+#include <spi.h>
+#include <stdio_dev.h>
+#include <asm-generic/gpio.h>
+#include <linux/delay.h>
+#include <linux/input.h>
+
+/*
+ * The Apple SPI keyboard controller implements a protocol that
+ * closely resembles HID Keyboard Boot protocol.  The key codes are
+ * mapped according to the HID Keyboard/Keypad Usage Table.
+ */
+
+/* Modifier key bits */
+#define HID_MOD_LEFTCTRL	BIT(0)
+#define HID_MOD_LEFTSHIFT	BIT(1)
+#define HID_MOD_LEFTALT		BIT(2)
+#define HID_MOD_LEFTGUI		BIT(3)
+#define HID_MOD_RIGHTCTRL	BIT(4)
+#define HID_MOD_RIGHTSHIFT	BIT(5)
+#define HID_MOD_RIGHTALT	BIT(6)
+#define HID_MOD_RIGHTGUI	BIT(7)
+
+static const u8 hid_kbd_keymap[] = {
+	KEY_RESERVED, 0xff, 0xff, 0xff,
+	KEY_A, KEY_B, KEY_C, KEY_D,
+	KEY_E, KEY_F, KEY_G, KEY_H,
+	KEY_I, KEY_J, KEY_K, KEY_L,
+	KEY_M, KEY_N, KEY_O, KEY_P,
+	KEY_Q, KEY_R, KEY_S, KEY_T,
+	KEY_U, KEY_V, KEY_W, KEY_X,
+	KEY_Y, KEY_Z, KEY_1, KEY_2,
+	KEY_3, KEY_4, KEY_5, KEY_6,
+	KEY_7, KEY_8, KEY_9, KEY_0,
+	KEY_ENTER, KEY_ESC, KEY_BACKSPACE, KEY_TAB,
+	KEY_SPACE, KEY_MINUS, KEY_EQUAL, KEY_LEFTBRACE,
+	KEY_RIGHTBRACE, KEY_BACKSLASH, 0xff, KEY_SEMICOLON,
+	KEY_APOSTROPHE, KEY_GRAVE, KEY_COMMA, KEY_DOT,
+	KEY_SLASH, KEY_CAPSLOCK, KEY_F1, KEY_F2,
+	KEY_F3, KEY_F4, KEY_F5, KEY_F6,
+	KEY_F7, KEY_F8, KEY_F9, KEY_F10,
+	KEY_F11, KEY_F12, KEY_SYSRQ, KEY_SCROLLLOCK,
+	KEY_PAUSE, KEY_INSERT, KEY_HOME, KEY_PAGEUP,
+	KEY_DELETE, KEY_END, KEY_PAGEDOWN, KEY_RIGHT,
+	KEY_LEFT, KEY_DOWN, KEY_UP, KEY_NUMLOCK,
+	KEY_KPSLASH, KEY_KPASTERISK, KEY_KPMINUS, KEY_KPPLUS,
+	KEY_KPENTER, KEY_KP1, KEY_KP2, KEY_KP3,
+	KEY_KP4, KEY_KP5, KEY_KP6, KEY_KP7,
+	KEY_KP8, KEY_KP9, KEY_KP0, KEY_KPDOT,
+	KEY_BACKSLASH, KEY_COMPOSE, KEY_POWER, KEY_KPEQUAL,
+};
+
+/* Report ID used for keyboard input reports. */
+#define KBD_REPORTID	0x01
+
+struct apple_spi_kbd_report {
+	u8 reportid;
+	u8 modifiers;
+	u8 reserved;
+	u8 keycode[6];
+	u8 fn;
+};
+
+struct apple_spi_kbd_priv {
+	struct gpio_desc enable;
+	struct apple_spi_kbd_report old; /* previous keyboard input report */
+	struct apple_spi_kbd_report new; /* current keyboard input report */
+};
+
+/* Keyboard device. */
+#define KBD_DEVICE	0x01
+
+/* The controller sends us fixed-size packets of 256 bytes. */
+struct apple_spi_kbd_packet {
+	u8 flags;
+#define PACKET_READ	0x20
+	u8 device;
+	u16 offset;
+	u16 remaining;
+	u16 len;
+	u8 data[246];
+	u16 crc;
+};
+
+/* Packets contain a single variable-sized message. */
+struct apple_spi_kbd_msg {
+	u8 type;
+#define MSG_REPORT	0x10
+	u8 device;
+	u8 unknown;
+	u8 msgid;
+	u16 rsplen;
+	u16 cmdlen;
+	u8 data[0];
+};
+
+static void apple_spi_kbd_service_modifiers(struct input_config *input)
+{
+	struct apple_spi_kbd_priv *priv = dev_get_priv(input->dev);
+	u8 new = priv->new.modifiers;
+	u8 old = priv->old.modifiers;
+
+	if ((new ^ old) & HID_MOD_LEFTCTRL)
+		input_add_keycode(input, KEY_LEFTCTRL,
+				  old & HID_MOD_LEFTCTRL);
+	if ((new ^ old) & HID_MOD_RIGHTCTRL)
+		input_add_keycode(input, KEY_RIGHTCTRL,
+				  old & HID_MOD_RIGHTCTRL);
+	if ((new ^ old) & HID_MOD_LEFTSHIFT)
+		input_add_keycode(input, KEY_LEFTSHIFT,
+				  old & HID_MOD_LEFTSHIFT);
+	if ((new ^ old) & HID_MOD_RIGHTSHIFT)
+		input_add_keycode(input, KEY_RIGHTSHIFT,
+				  old & HID_MOD_RIGHTSHIFT);
+	if ((new ^ old) & HID_MOD_LEFTALT)
+		input_add_keycode(input, KEY_LEFTALT,
+				  old & HID_MOD_LEFTALT);
+	if ((new ^ old) & HID_MOD_RIGHTALT)
+		input_add_keycode(input, KEY_RIGHTALT,
+				  old & HID_MOD_RIGHTALT);
+	if ((new ^ old) & HID_MOD_LEFTGUI)
+		input_add_keycode(input, KEY_LEFTMETA,
+				  old & HID_MOD_LEFTGUI);
+	if ((new ^ old) & HID_MOD_RIGHTGUI)
+		input_add_keycode(input, KEY_RIGHTMETA,
+				  old & HID_MOD_RIGHTGUI);
+}
+
+static void apple_spi_kbd_service_key(struct input_config *input, int i,
+				      int released)
+{
+	struct apple_spi_kbd_priv *priv = dev_get_priv(input->dev);
+	u8 *new;
+	u8 *old;
+
+	if (released) {
+		new = priv->new.keycode;
+		old = priv->old.keycode;
+	} else {
+		new = priv->old.keycode;
+		old = priv->new.keycode;
+	}
+
+	if (memscan(new, old[i], sizeof(priv->new.keycode)) ==
+	    new + sizeof(priv->new.keycode) &&
+	    old[i] < ARRAY_SIZE(hid_kbd_keymap))
+		input_add_keycode(input, hid_kbd_keymap[old[i]], released);
+}
+
+static int apple_spi_kbd_check(struct input_config *input)
+{
+	struct udevice *dev = input->dev;
+	struct apple_spi_kbd_priv *priv = dev_get_priv(dev);
+	struct apple_spi_kbd_packet packet;
+	struct apple_spi_kbd_msg *msg;
+	struct apple_spi_kbd_report *report;
+	int i, ret;
+
+	memset(&packet, 0, sizeof(packet));
+
+	ret = dm_spi_claim_bus(dev);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * The keyboard controller needs delays after asserting CS#
+	 * and before deasserting CS#.
+	 */
+	ret = dm_spi_xfer(dev, 0, NULL, NULL, SPI_XFER_BEGIN);
+	if (ret < 0)
+		goto fail;
+	udelay(100);
+	ret = dm_spi_xfer(dev, sizeof(packet) * 8, NULL, &packet, 0);
+	if (ret < 0)
+		goto fail;
+	udelay(100);
+	ret = dm_spi_xfer(dev, 0, NULL, NULL, SPI_XFER_END);
+	if (ret < 0)
+		goto fail;
+
+	dm_spi_release_bus(dev);
+
+	/*
+	 * The keyboard controller needs a delay between subsequent
+	 * SPI transfers.
+	 */
+	udelay(250);
+
+	msg = (struct apple_spi_kbd_msg *)packet.data;
+	report = (struct apple_spi_kbd_report *)msg->data;
+	if (packet.flags == PACKET_READ && packet.device == KBD_DEVICE &&
+	    msg->type == MSG_REPORT && msg->device == KBD_DEVICE &&
+	    msg->cmdlen == sizeof(struct apple_spi_kbd_report) &&
+	    report->reportid == KBD_REPORTID) {
+		memcpy(&priv->new, report,
+		       sizeof(struct apple_spi_kbd_report));
+		apple_spi_kbd_service_modifiers(input);
+		for (i = 0; i < sizeof(priv->new.keycode); i++) {
+			apple_spi_kbd_service_key(input, i, 1);
+			apple_spi_kbd_service_key(input, i, 0);
+		}
+		memcpy(&priv->old, &priv->new,
+		       sizeof(struct apple_spi_kbd_report));
+		return 1;
+	}
+
+	return 0;
+
+fail:
+	/*
+	 * Make sure CS# is deasserted. If this fails there is nothing
+	 * we can do, so ignore any errors.
+	 */
+	dm_spi_xfer(dev, 0, NULL, NULL, SPI_XFER_END);
+	dm_spi_release_bus(dev);
+	return ret;
+}
+
+static int apple_spi_kbd_probe(struct udevice *dev)
+{
+	struct apple_spi_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;
+
+	ret = gpio_request_by_name(dev, "spien-gpios", 0, &priv->enable,
+				   GPIOD_IS_OUT);
+	if (ret < 0)
+		return ret;
+
+	/* Reset the keyboard controller. */
+	dm_gpio_set_value(&priv->enable, 1);
+	udelay(5000);
+	dm_gpio_set_value(&priv->enable, 0);
+	udelay(5000);
+
+	/* Enable the keyboard controller. */
+	dm_gpio_set_value(&priv->enable, 1);
+
+	input->dev = dev;
+	input->read_keys = apple_spi_kbd_check;
+	input_add_tables(input, false);
+	strcpy(sdev->name, "spikbd");
+
+	return input_stdio_register(sdev);
+}
+
+static const struct keyboard_ops apple_spi_kbd_ops = {
+};
+
+static const struct udevice_id apple_spi_kbd_of_match[] = {
+	{ .compatible = "apple,spi-hid-transport" },
+	{ /* sentinel */ }
+};
+
+U_BOOT_DRIVER(apple_spi_kbd) = {
+	.name = "apple_spi_kbd",
+	.id = UCLASS_KEYBOARD,
+	.of_match = apple_spi_kbd_of_match,
+	.probe = apple_spi_kbd_probe,
+	.priv_auto = sizeof(struct apple_spi_kbd_priv),
+	.ops = &apple_spi_kbd_ops,
+};