HSI: Introduce Nokia N900 modem driver

The Nokia N900's modem is connected via Synchronous Serial Interface (SSI),
which is a legacy version of MIPI's High-speed Synchronous Serial Interface
(HSI).

The handles the GPIOs for enabling and resetting the modem and instanciates
ssi-protocol for data exchange. It does not yet support exchanging voice data
with the modem.

Signed-off-by: Sebastian Reichel <sre@kernel.org>
Reviewed-by: Pavel Machek <pavel@ucw.cz>
Tested-By: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>

3 files changed, 295 insertions, 0 deletions

diff --git a/drivers/hsi/clients/Kconfig b/drivers/hsi/clients/Kconfig
index 1457cfb5b453..71b9f9ab86e4 100644
--- a/drivers/hsi/clients/Kconfig
+++ b/drivers/hsi/clients/Kconfig
@@ -4,6 +4,15 @@
 
 comment "HSI clients"
 
+config NOKIA_MODEM
+        tristate "Nokia Modem"
+        depends on HSI && SSI_PROTOCOL
+        help
+        Say Y here if you want to add support for the modem on Nokia
+        N900 (Nokia RX-51) hardware.
+
+        If unsure, say N.
+
 config SSI_PROTOCOL
         tristate "SSI protocol"
         depends on HSI && PHONET && (OMAP_SSI=y || OMAP_SSI=m)
diff --git a/drivers/hsi/clients/Makefile b/drivers/hsi/clients/Makefile
index ccbf768ea42b..4d5bc0e0b27b 100644
--- a/drivers/hsi/clients/Makefile
+++ b/drivers/hsi/clients/Makefile
@@ -2,5 +2,6 @@
 # Makefile for HSI clients
 #
 
+obj-$(CONFIG_NOKIA_MODEM)       += nokia-modem.o
 obj-$(CONFIG_SSI_PROTOCOL)      += ssi_protocol.o
 obj-$(CONFIG_HSI_CHAR)          += hsi_char.o
diff --git a/drivers/hsi/clients/nokia-modem.c b/drivers/hsi/clients/nokia-modem.c
new file mode 100644
index 000000000000..363b780dacea
--- /dev/null
+++ b/drivers/hsi/clients/nokia-modem.c
@@ -0,0 +1,285 @@
+/*
+ * nokia-modem.c
+ *
+ * HSI client driver for Nokia N900 modem.
+ *
+ * Copyright (C) 2014 Sebastian Reichel <sre@kernel.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA
+ */
+
+#include <linux/gpio/consumer.h>
+#include <linux/hsi/hsi.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/of_gpio.h>
+#include <linux/hsi/ssi_protocol.h>
+
+static unsigned int pm;
+module_param(pm, int, 0400);
+MODULE_PARM_DESC(pm,
+        "Enable power management (0=disabled, 1=userland based [default])");
+
+struct nokia_modem_gpio {
+        struct gpio_desc        *gpio;
+        const char              *name;
+};
+
+struct nokia_modem_device {
+        struct tasklet_struct   nokia_modem_rst_ind_tasklet;
+        int                     nokia_modem_rst_ind_irq;
+        struct device           *device;
+        struct nokia_modem_gpio *gpios;
+        int                     gpio_amount;
+        struct hsi_client       *ssi_protocol;
+};
+
+static void do_nokia_modem_rst_ind_tasklet(unsigned long data)
+{
+        struct nokia_modem_device *modem = (struct nokia_modem_device *)data;
+
+        if (!modem)
+                return;
+
+        dev_info(modem->device, "CMT rst line change detected\n");
+
+        if (modem->ssi_protocol)
+                ssip_reset_event(modem->ssi_protocol);
+}
+
+static irqreturn_t nokia_modem_rst_ind_isr(int irq, void *data)
+{
+        struct nokia_modem_device *modem = (struct nokia_modem_device *)data;
+
+        tasklet_schedule(&modem->nokia_modem_rst_ind_tasklet);
+
+        return IRQ_HANDLED;
+}
+
+static void nokia_modem_gpio_unexport(struct device *dev)
+{
+        struct nokia_modem_device *modem = dev_get_drvdata(dev);
+        int i;
+
+        for (i = 0; i < modem->gpio_amount; i++) {
+                sysfs_remove_link(&dev->kobj, modem->gpios[i].name);
+                gpiod_unexport(modem->gpios[i].gpio);
+        }
+}
+
+static int nokia_modem_gpio_probe(struct device *dev)
+{
+        struct device_node *np = dev->of_node;
+        struct nokia_modem_device *modem = dev_get_drvdata(dev);
+        int gpio_count, gpio_name_count, i, err;
+
+        gpio_count = of_gpio_count(np);
+
+        if (gpio_count < 0) {
+                dev_err(dev, "missing gpios: %d\n", gpio_count);
+                return gpio_count;
+        }
+
+        gpio_name_count = of_property_count_strings(np, "gpio-names");
+
+        if (gpio_count != gpio_name_count) {
+                dev_err(dev, "number of gpios does not equal number of gpio names\n");
+                return -EINVAL;
+        }
+
+        modem->gpios = devm_kzalloc(dev, gpio_count *
+                                sizeof(struct nokia_modem_gpio), GFP_KERNEL);
+        if (!modem->gpios) {
+                dev_err(dev, "Could not allocate memory for gpios\n");
+                return -ENOMEM;
+        }
+
+        modem->gpio_amount = gpio_count;
+
+        for (i = 0; i < gpio_count; i++) {
+                modem->gpios[i].gpio = devm_gpiod_get_index(dev, NULL, i);
+                if (IS_ERR(modem->gpios[i].gpio)) {
+                        dev_err(dev, "Could not get gpio %d\n", i);
+                        return PTR_ERR(modem->gpios[i].gpio);
+                }
+
+                err = of_property_read_string_index(np, "gpio-names", i,
+                                                &(modem->gpios[i].name));
+                if (err) {
+                        dev_err(dev, "Could not get gpio name %d\n", i);
+                        return err;
+                }
+
+                err = gpiod_direction_output(modem->gpios[i].gpio, 0);
+                if (err)
+                        return err;
+
+                err = gpiod_export(modem->gpios[i].gpio, 0);
+                if (err)
+                        return err;
+
+                err = gpiod_export_link(dev, modem->gpios[i].name,
+                                                        modem->gpios[i].gpio);
+                if (err)
+                        return err;
+        }
+
+        return 0;
+}
+
+static int nokia_modem_probe(struct device *dev)
+{
+        struct device_node *np;
+        struct nokia_modem_device *modem;
+        struct hsi_client *cl = to_hsi_client(dev);
+        struct hsi_port *port = hsi_get_port(cl);
+        int irq, pflags, err;
+        struct hsi_board_info ssip;
+
+        np = dev->of_node;
+        if (!np) {
+                dev_err(dev, "device tree node not found\n");
+                return -ENXIO;
+        }
+
+        modem = devm_kzalloc(dev, sizeof(*modem), GFP_KERNEL);
+        if (!modem) {
+                dev_err(dev, "Could not allocate memory for nokia_modem_device\n");
+                return -ENOMEM;
+        }
+        dev_set_drvdata(dev, modem);
+
+        irq = irq_of_parse_and_map(np, 0);
+        if (irq < 0) {
+                dev_err(dev, "Invalid rst_ind interrupt (%d)\n", irq);
+                return irq;
+        }
+        modem->nokia_modem_rst_ind_irq = irq;
+        pflags = irq_get_trigger_type(irq);
+
+        tasklet_init(&modem->nokia_modem_rst_ind_tasklet,
+                        do_nokia_modem_rst_ind_tasklet, (unsigned long)modem);
+        err = devm_request_irq(dev, irq, nokia_modem_rst_ind_isr,
+                                IRQF_DISABLED | pflags, "modem_rst_ind", modem);
+        if (err < 0) {
+                dev_err(dev, "Request rst_ind irq(%d) failed (flags %d)\n",
+                                                                irq, pflags);
+                return err;
+        }
+        enable_irq_wake(irq);
+
+        if(pm) {
+                err = nokia_modem_gpio_probe(dev);
+                if (err < 0) {
+                        dev_err(dev, "Could not probe GPIOs\n");
+                        goto error1;
+                }
+        }
+
+        ssip.name = "ssi-protocol";
+        ssip.tx_cfg = cl->tx_cfg;
+        ssip.rx_cfg = cl->rx_cfg;
+        ssip.platform_data = NULL;
+        ssip.archdata = NULL;
+
+        modem->ssi_protocol = hsi_new_client(port, &ssip);
+        if (!modem->ssi_protocol) {
+                dev_err(dev, "Could not register ssi-protocol device\n");
+                goto error2;
+        }
+
+        err = device_attach(&modem->ssi_protocol->device);
+        if (err == 0) {
+                dev_err(dev, "Missing ssi-protocol driver\n");
+                err = -EPROBE_DEFER;
+                goto error3;
+        } else if (err < 0) {
+                dev_err(dev, "Could not load ssi-protocol driver (%d)\n", err);
+                goto error3;
+        }
+
+        /* TODO: register cmt-speech hsi client */
+
+        dev_info(dev, "Registered Nokia HSI modem\n");
+
+        return 0;
+
+error3:
+        hsi_remove_client(&modem->ssi_protocol->device, NULL);
+error2:
+        nokia_modem_gpio_unexport(dev);
+error1:
+        disable_irq_wake(modem->nokia_modem_rst_ind_irq);
+        tasklet_kill(&modem->nokia_modem_rst_ind_tasklet);
+
+        return err;
+}
+
+static int nokia_modem_remove(struct device *dev)
+{
+        struct nokia_modem_device *modem = dev_get_drvdata(dev);
+
+        if (!modem)
+                return 0;
+
+        if (modem->ssi_protocol) {
+                hsi_remove_client(&modem->ssi_protocol->device, NULL);
+                modem->ssi_protocol = NULL;
+        }
+
+        nokia_modem_gpio_unexport(dev);
+        dev_set_drvdata(dev, NULL);
+        disable_irq_wake(modem->nokia_modem_rst_ind_irq);
+        tasklet_kill(&modem->nokia_modem_rst_ind_tasklet);
+
+        return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id nokia_modem_of_match[] = {
+        { .compatible = "nokia,n900-modem", },
+        {},
+};
+MODULE_DEVICE_TABLE(of, nokia_modem_of_match);
+#endif
+
+static struct hsi_client_driver nokia_modem_driver = {
+        .driver = {
+                .name   = "nokia-modem",
+                .owner  = THIS_MODULE,
+                .probe  = nokia_modem_probe,
+                .remove = nokia_modem_remove,
+                .of_match_table = of_match_ptr(nokia_modem_of_match),
+        },
+};
+
+static int __init nokia_modem_init(void)
+{
+        return hsi_register_client_driver(&nokia_modem_driver);
+}
+module_init(nokia_modem_init);
+
+static void __exit nokia_modem_exit(void)
+{
+        hsi_unregister_client_driver(&nokia_modem_driver);
+}
+module_exit(nokia_modem_exit);
+
+MODULE_ALIAS("hsi:nokia-modem");
+MODULE_AUTHOR("Sebastian Reichel <sre@kernel.org>");
+MODULE_DESCRIPTION("HSI driver module for Nokia N900 Modem");
+MODULE_LICENSE("GPL");