Input: add OLPC AP-SP driver

The OLPC XO-1.75 and XO-4 laptops include a PS/2 touchpad and an AT
keyboard, yet they do not have a hardware PS/2 controller. Instead, a
firmware runs on a dedicated core ("Security Processor", part of the SoC)
that acts as a PS/2 controller through bit-banging.

Communication between the main cpu (Application Processor) and the
Security Processor happens via a standard command mechanism implemented
by the SoC. Add a driver for this interface to enable keyboard/mouse
input on this platform.

Original author: Saadia Baloch
Signed-off-by: Daniel Drake <[e-mail]>
Signed-off-by: Dmitry Torokhov <[e-mail]>

Documentation/devicetree/bindings/serio/olpc,ap-sp.txt

···
+OLPC AP-SP serio interface
+
+Required properties:
+- compatible : "olpc,ap-sp"
+- reg : base address and length of SoC's WTM registers
+- interrupts : SP-AP interrupt
+
+Example:
+	ap-sp@d4290000 {
+		compatible = "olpc,ap-sp";
+		reg = <0xd4290000 0x1000>;
+		interrupts = <40>;
+	}

drivers/input/serio/Kconfig

···
 	  To compile this driver as a module, choose M here: the module will
 	  be called apbps2.
 
+config SERIO_OLPC_APSP
+	tristate "OLPC AP-SP input support"
+	depends on OF
+	help
+	  Say Y here if you want support for the keyboard and touchpad included
+	  in the OLPC XO-1.75 and XO-4 laptops.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called olpc_apsp.
+
 endif

drivers/input/serio/Makefile

···
 obj-$(CONFIG_SERIO_ALTERA_PS2)	+= altera_ps2.o
 obj-$(CONFIG_SERIO_ARC_PS2)	+= arc_ps2.o
 obj-$(CONFIG_SERIO_APBPS2)	+= apbps2.o
+obj-$(CONFIG_SERIO_OLPC_APSP)	+= olpc_apsp.o

drivers/input/serio/olpc_apsp.c

···
+/*
+ * OLPC serio driver for multiplexed input from Marvell MMP security processor
+ *
+ * Copyright (C) 2011-2013 One Laptop Per Child
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/init.h>
+#include <linux/serio.h>
+#include <linux/err.h>
+#include <linux/platform_device.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/delay.h>
+
+/*
+ * The OLPC XO-1.75 and XO-4 laptops do not have a hardware PS/2 controller.
+ * Instead, the OLPC firmware runs a bit-banging PS/2 implementation on an
+ * otherwise-unused slow processor which is included in the Marvell MMP2/MMP3
+ * SoC, known as the "Security Processor" (SP) or "Wireless Trusted Module"
+ * (WTM). This firmware then reports its results via the WTM registers,
+ * which we read from the Application Processor (AP, i.e. main CPU) in this
+ * driver.
+ *
+ * On the hardware side we have a PS/2 mouse and an AT keyboard, the data
+ * is multiplexed through this system. We create a serio port for each one,
+ * and demultiplex the data accordingly.
+ */
+
+/* WTM register offsets */
+#define SECURE_PROCESSOR_COMMAND	0x40
+#define COMMAND_RETURN_STATUS		0x80
+#define COMMAND_FIFO_STATUS		0xc4
+#define PJ_RST_INTERRUPT		0xc8
+#define PJ_INTERRUPT_MASK		0xcc
+
+/*
+ * The upper byte of SECURE_PROCESSOR_COMMAND and COMMAND_RETURN_STATUS is
+ * used to identify which port (device) is being talked to. The lower byte
+ * is the data being sent/received.
+ */
+#define PORT_MASK	0xff00
+#define DATA_MASK	0x00ff
+#define PORT_SHIFT	8
+#define KEYBOARD_PORT	0
+#define TOUCHPAD_PORT	1
+
+/* COMMAND_FIFO_STATUS */
+#define CMD_CNTR_MASK		0x7 /* Number of pending/unprocessed commands */
+#define MAX_PENDING_CMDS	4   /* from device specs */
+
+/* PJ_RST_INTERRUPT */
+#define SP_COMMAND_COMPLETE_RESET	0x1
+
+/* PJ_INTERRUPT_MASK */
+#define INT_0	(1 << 0)
+
+/* COMMAND_FIFO_STATUS */
+#define CMD_STS_MASK	0x100
+
+struct olpc_apsp {
+	struct device *dev;
+	struct serio *kbio;
+	struct serio *padio;
+	void __iomem *base;
+	int open_count;
+	int irq;
+};
+
+static int olpc_apsp_write(struct serio *port, unsigned char val)
+{
+	struct olpc_apsp *priv = port->port_data;
+	unsigned int i;
+	u32 which = 0;
+
+	if (port == priv->padio)
+		which = TOUCHPAD_PORT << PORT_SHIFT;
+	else
+		which = KEYBOARD_PORT << PORT_SHIFT;
+
+	dev_dbg(priv->dev, "olpc_apsp_write which=%x val=%x\n", which, val);
+	for (i = 0; i < 50; i++) {
+		u32 sts = readl(priv->base + COMMAND_FIFO_STATUS);
+		if ((sts & CMD_CNTR_MASK) < MAX_PENDING_CMDS) {
+			writel(which | val,
+			       priv->base + SECURE_PROCESSOR_COMMAND);
+			return 0;
+		}
+		/* SP busy. This has not been seen in practice. */
+		mdelay(1);
+	}
+
+	dev_dbg(priv->dev, "olpc_apsp_write timeout, status=%x\n",
+		readl(priv->base + COMMAND_FIFO_STATUS));
+
+	return -ETIMEDOUT;
+}
+
+static irqreturn_t olpc_apsp_rx(int irq, void *dev_id)
+{
+	struct olpc_apsp *priv = dev_id;
+	unsigned int w, tmp;
+	struct serio *serio;
+
+	/*
+	 * Write 1 to PJ_RST_INTERRUPT to acknowledge and clear the interrupt
+	 * Write 0xff00 to SECURE_PROCESSOR_COMMAND.
+	 */
+	tmp = readl(priv->base + PJ_RST_INTERRUPT);
+	if (!(tmp & SP_COMMAND_COMPLETE_RESET)) {
+		dev_warn(priv->dev, "spurious interrupt?\n");
+		return IRQ_NONE;
+	}
+
+	w = readl(priv->base + COMMAND_RETURN_STATUS);
+	dev_dbg(priv->dev, "olpc_apsp_rx %x\n", w);
+
+	if (w >> PORT_SHIFT == KEYBOARD_PORT)
+		serio = priv->kbio;
+	else
+		serio = priv->padio;
+
+	serio_interrupt(serio, w & DATA_MASK, 0);
+
+	/* Ack and clear interrupt */
+	writel(tmp | SP_COMMAND_COMPLETE_RESET, priv->base + PJ_RST_INTERRUPT);
+	writel(PORT_MASK, priv->base + SECURE_PROCESSOR_COMMAND);
+
+	pm_wakeup_event(priv->dev, 1000);
+	return IRQ_HANDLED;
+}
+
+static int olpc_apsp_open(struct serio *port)
+{
+	struct olpc_apsp *priv = port->port_data;
+	unsigned int tmp;
+
+	if (priv->open_count++ == 0) {
+		/* Enable interrupt 0 by clearing its bit */
+		tmp = readl(priv->base + PJ_INTERRUPT_MASK);
+		writel(tmp & ~INT_0, priv->base + PJ_INTERRUPT_MASK);
+	}
+
+	return 0;
+}
+
+static void olpc_apsp_close(struct serio *port)
+{
+	struct olpc_apsp *priv = port->port_data;
+	unsigned int tmp;
+
+	if (--priv->open_count == 0) {
+		/* Disable interrupt 0 */
+		tmp = readl(priv->base + PJ_INTERRUPT_MASK);
+		writel(tmp | INT_0, priv->base + PJ_INTERRUPT_MASK);
+	}
+}
+
+static int olpc_apsp_probe(struct platform_device *pdev)
+{
+	struct serio *kb_serio, *pad_serio;
+	struct olpc_apsp *priv;
+	struct resource *res;
+	struct device_node *np;
+	unsigned long l;
+	int error;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(struct olpc_apsp), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	np = pdev->dev.of_node;
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENOENT;
+
+	priv->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(priv->base)) {
+		dev_err(&pdev->dev, "Failed to map WTM registers\n");
+		return PTR_ERR(priv->base);
+	}
+
+	priv->irq = platform_get_irq(pdev, 0);
+	if (priv->irq < 0)
+		return priv->irq;
+
+	l = readl(priv->base + COMMAND_FIFO_STATUS);
+	if (!(l & CMD_STS_MASK)) {
+		dev_err(&pdev->dev, "SP cannot accept commands.\n");
+		return -EIO;
+	}
+
+	/* KEYBOARD */
+	kb_serio = kzalloc(sizeof(struct serio), GFP_KERNEL);
+	if (!kb_serio)
+		return -ENOMEM;
+	kb_serio->id.type	= SERIO_8042_XL;
+	kb_serio->write		= olpc_apsp_write;
+	kb_serio->open		= olpc_apsp_open;
+	kb_serio->close		= olpc_apsp_close;
+	kb_serio->port_data	= priv;
+	kb_serio->dev.parent	= &pdev->dev;
+	strlcpy(kb_serio->name, "sp keyboard", sizeof(kb_serio->name));
+	strlcpy(kb_serio->phys, "sp/serio0", sizeof(kb_serio->phys));
+	priv->kbio		= kb_serio;
+	serio_register_port(kb_serio);
+
+	/* TOUCHPAD */
+	pad_serio = kzalloc(sizeof(struct serio), GFP_KERNEL);
+	if (!pad_serio) {
+		error = -ENOMEM;
+		goto err_pad;
+	}
+	pad_serio->id.type	= SERIO_8042;
+	pad_serio->write	= olpc_apsp_write;
+	pad_serio->open		= olpc_apsp_open;
+	pad_serio->close	= olpc_apsp_close;
+	pad_serio->port_data	= priv;
+	pad_serio->dev.parent	= &pdev->dev;
+	strlcpy(pad_serio->name, "sp touchpad", sizeof(pad_serio->name));
+	strlcpy(pad_serio->phys, "sp/serio1", sizeof(pad_serio->phys));
+	priv->padio		= pad_serio;
+	serio_register_port(pad_serio);
+
+	error = request_irq(priv->irq, olpc_apsp_rx, 0, "olpc-apsp", priv);
+	if (error) {
+		dev_err(&pdev->dev, "Failed to request IRQ\n");
+		goto err_irq;
+	}
+
+	priv->dev = &pdev->dev;
+	device_init_wakeup(priv->dev, 1);
+	platform_set_drvdata(pdev, priv);
+
+	dev_dbg(&pdev->dev, "probed successfully.\n");
+	return 0;
+
+err_irq:
+	serio_unregister_port(pad_serio);
+err_pad:
+	serio_unregister_port(kb_serio);
+	return error;
+}
+
+static int olpc_apsp_remove(struct platform_device *pdev)
+{
+	struct olpc_apsp *priv = platform_get_drvdata(pdev);
+
+	free_irq(priv->irq, priv);
+
+	serio_unregister_port(priv->kbio);
+	serio_unregister_port(priv->padio);
+
+	return 0;
+}
+
+static struct of_device_id olpc_apsp_dt_ids[] = {
+	{ .compatible = "olpc,ap-sp", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, olpc_apsp_dt_ids);
+
+static struct platform_driver olpc_apsp_driver = {
+	.probe		= olpc_apsp_probe,
+	.remove		= olpc_apsp_remove,
+	.driver		= {
+		.name	= "olpc-apsp",
+		.owner	= THIS_MODULE,
+		.of_match_table = olpc_apsp_dt_ids,
+	},
+};
+
+MODULE_DESCRIPTION("OLPC AP-SP serio driver");
+MODULE_LICENSE("GPL");
+module_platform_driver(olpc_apsp_driver);