/*
 * 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/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);
        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 const 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",
                .of_match_table = olpc_apsp_dt_ids,
        },
};

MODULE_DESCRIPTION("OLPC AP-SP serio driver");
MODULE_LICENSE("GPL");
module_platform_driver(olpc_apsp_driver);