[v5,13/13] tty: gunyah: Add tty console driver for RM Console Services

diff --git a/MAINTAINERS b/MAINTAINERS
index 8a3d79b56698..e85140fa0dfe 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8889,6 +8889,7 @@  F:	Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml
 F:	Documentation/virt/gunyah/
 F:	arch/arm64/gunyah/
 F:	drivers/mailbox/gunyah-msgq.c
+F:	drivers/tty/gunyah_tty.c
 F:	drivers/virt/gunyah/
 F:	include/asm-generic/gunyah.h
 F:	include/linux/gunyah*.h
diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index cc30ff93e2e4..ff86e977f9ac 100644
--- a/drivers/tty/Kconfig
+++ b/drivers/tty/Kconfig
@@ -380,6 +380,14 @@  config RPMSG_TTY
 	  To compile this driver as a module, choose M here: the module will be
 	  called rpmsg_tty.
 
+config GUNYAH_CONSOLE
+	tristate "Gunyah Consoles"
+	depends on GUNYAH
+	help
+	  This enables support for console output using Gunyah's Resource Manager RPC.
+	  This is normally used when a secondary VM which does not have exclusive access
+	  to a real or virtualized serial device and virtio-console is unavailable.
+
 endif # TTY
 
 source "drivers/tty/serdev/Kconfig"
diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile
index 07aca5184a55..134b7321c630 100644
--- a/drivers/tty/Makefile
+++ b/drivers/tty/Makefile
@@ -27,5 +27,6 @@  obj-$(CONFIG_GOLDFISH_TTY)	+= goldfish.o
 obj-$(CONFIG_MIPS_EJTAG_FDC_TTY) += mips_ejtag_fdc.o
 obj-$(CONFIG_VCC)		+= vcc.o
 obj-$(CONFIG_RPMSG_TTY)		+= rpmsg_tty.o
+obj-$(CONFIG_GUNYAH_CONSOLE)	+= gunyah_console.o
 
 obj-y += ipwireless/
diff --git a/drivers/tty/gunyah_console.c b/drivers/tty/gunyah_console.c
new file mode 100644
index 000000000000..71d9f22c2a43
--- /dev/null
+++ b/drivers/tty/gunyah_console.c
@@ -0,0 +1,439 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+
+#include <linux/console.h>
+#include <linux/kfifo.h>
+#include <linux/kref.h>
+#include <linux/gunyah_rsc_mgr.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/workqueue.h>
+
+/*
+ * The Linux TTY code requires us to know ahead of time how many ports we might
+ * need. Each port here corresponds to a VM. 16 seems like a reasonable number
+ * of ports for systems that are running Gunyah and using the console interface.
+ */
+#define RM_CONS_TTY_ADAPATERS		(16)
+
+struct rm_cons_port {
+	struct tty_port port;
+	u16 vmid;
+	unsigned int index;
+};
+
+struct rm_cons_drv_data {
+	struct tty_driver *tty_driver;
+	struct device *dev;
+
+	spinlock_t ports_lock;
+	struct rm_cons_port *ports[RM_CONS_TTY_ADAPATERS];
+
+	struct notifier_block rm_cons_notif;
+	struct console console;
+
+	/* below are for printk console.
+	 * gh_rm_console_* calls will sleep and console_write can be called from
+	 * atomic ctx. Two xmit buffers are used. The active buffer is tracked with
+	 * co_xmit_idx. Writes go into the co_xmit_buf[co_xmit_idx] buffer.
+	 * A work is scheduled to flush the bytes. The work will swap the active buffer
+	 * and write out the other buffer.
+	 */
+	char *co_xmit_buf[2];
+	int co_xmit_idx;
+	unsigned int co_xmit_count;
+	spinlock_t co_xmit_lock;
+	struct work_struct co_flush_work;
+};
+
+static int rm_cons_notif_handler(struct notifier_block *nb, unsigned long cmd, void *data)
+{
+	int count, i;
+	struct rm_cons_port *rm_port = NULL;
+	struct tty_port *tty_port = NULL;
+	struct rm_cons_drv_data *cons_data =
+		container_of(nb, struct rm_cons_drv_data, rm_cons_notif);
+	const struct gh_rm_notification *notif = data;
+	struct gh_rm_notif_vm_console_chars const * const msg = notif->buff;
+
+	if (cmd != GH_RM_NOTIF_VM_CONSOLE_CHARS ||
+		notif->size < sizeof(*msg))
+		return NOTIFY_DONE;
+
+	spin_lock(&cons_data->ports_lock);
+	for (i = 0; i < RM_CONS_TTY_ADAPATERS; i++) {
+		if (!cons_data->ports[i])
+			continue;
+		if (cons_data->ports[i]->vmid == msg->vmid) {
+			rm_port = cons_data->ports[i];
+			break;
+		}
+	}
+	if (rm_port)
+		tty_port = tty_port_get(&rm_port->port);
+	spin_unlock(&cons_data->ports_lock);
+
+	if (!rm_port)
+		dev_warn(cons_data->dev, "Received unexpected console characters for VMID %u\n",
+			msg->vmid);
+	if (!tty_port)
+		return NOTIFY_DONE;
+
+	count = tty_buffer_request_room(tty_port, msg->num_bytes);
+	tty_insert_flip_string(tty_port, msg->bytes, count);
+	tty_flip_buffer_push(tty_port);
+
+	tty_port_put(tty_port);
+	return NOTIFY_OK;
+}
+
+static int rm_cons_tty_open(struct tty_struct *tty, struct file *filp)
+{
+	struct rm_cons_port *rm_port = dev_get_drvdata(tty->dev);
+
+	return tty_port_open(&rm_port->port, tty, filp);
+}
+
+static void rm_cons_tty_close(struct tty_struct *tty, struct file *filp)
+{
+	struct rm_cons_port *rm_port = dev_get_drvdata(tty->dev);
+
+	tty_port_close(&rm_port->port, tty, filp);
+}
+
+static int rm_cons_tty_write(struct tty_struct *tty, const unsigned char *buf, int count)
+{
+	struct rm_cons_port *rm_port = dev_get_drvdata(tty->dev);
+	int ret;
+
+	if (!count)
+		return 0;
+
+	ret = gh_rm_console_write(rm_port->vmid, buf, count);
+	if (ret)
+		return -EAGAIN;
+	return count;
+}
+
+static void rm_cons_tty_flush_chars(struct tty_struct *tty)
+{
+	struct rm_cons_port *rm_port = dev_get_drvdata(tty->dev);
+
+	gh_rm_console_flush(rm_port->vmid);
+}
+
+static unsigned int rm_cons_mgr_tty_write_room(struct tty_struct *tty)
+{
+	return GH_RM_CONSOLE_WRITE_CHARS;
+}
+
+static const struct tty_operations rm_cons_tty_ops = {
+	.open = rm_cons_tty_open,
+	.close = rm_cons_tty_close,
+	.write = rm_cons_tty_write,
+	.flush_chars = rm_cons_tty_flush_chars,
+	.write_room = rm_cons_mgr_tty_write_room,
+};
+
+static int rm_cons_port_activate(struct tty_port *port, struct tty_struct *tty)
+{
+	struct rm_cons_port *rm_port = container_of(port, struct rm_cons_port, port);
+
+	return gh_rm_console_open(rm_port->vmid);
+}
+
+static void rm_cons_port_shutdown(struct tty_port *port)
+{
+	struct rm_cons_port *rm_port = container_of(port, struct rm_cons_port, port);
+	int ret;
+
+	ret = gh_rm_console_close(rm_port->vmid);
+	if (ret)
+		dev_err(port->tty->dev, "Failed to close ttyGH%d: %d\n", rm_port->index, ret);
+}
+
+static void rm_cons_port_destruct(struct tty_port *port)
+{
+	struct rm_cons_port *rm_port = container_of(port, struct rm_cons_port, port);
+	struct rm_cons_drv_data *cons_data = dev_get_drvdata(port->tty->dev);
+
+	spin_lock(&cons_data->ports_lock);
+	cons_data->ports[rm_port->index] = NULL;
+	spin_unlock(&cons_data->ports_lock);
+	kfree(rm_port);
+}
+
+static const struct tty_port_operations rm_cons_port_ops = {
+	.activate = rm_cons_port_activate,
+	.shutdown = rm_cons_port_shutdown,
+	.destruct = rm_cons_port_destruct,
+};
+
+static void rm_cons_console_flush_work(struct work_struct *ws)
+{
+	struct rm_cons_drv_data *cons_data =
+		container_of(ws, struct rm_cons_drv_data, co_flush_work);
+	struct console *co = &cons_data->console;
+	struct rm_cons_port *rm_port = co->data;
+	unsigned long flags;
+	size_t size;
+	int ret, old_buf = cons_data->co_xmit_idx;
+
+	spin_lock_irqsave(&cons_data->co_xmit_lock, flags);
+	cons_data->co_xmit_idx = 1 - old_buf;
+	size = cons_data->co_xmit_count;
+	cons_data->co_xmit_count = 0;
+	spin_unlock_irqrestore(&cons_data->co_xmit_lock, flags);
+
+	do {
+		ret = gh_rm_console_write(rm_port->vmid, cons_data->co_xmit_buf[old_buf], size);
+	} while (ret && ret != -ENOMEM);
+
+	gh_rm_console_flush(rm_port->vmid);
+}
+
+static void rm_cons_console_write(struct console *co, const char *buf, unsigned count)
+{
+	struct rm_cons_drv_data *cons_data = container_of(co, struct rm_cons_drv_data, console);
+	unsigned long flags;
+
+	spin_lock_irqsave(&cons_data->co_xmit_lock, flags);
+	count = min(count, (unsigned)(PAGE_SIZE - cons_data->co_xmit_count));
+	memcpy(&cons_data->co_xmit_buf[cons_data->co_xmit_idx][cons_data->co_xmit_count], buf,
+		count);
+	cons_data->co_xmit_count += count;
+	spin_unlock_irqrestore(&cons_data->co_xmit_lock, flags);
+
+	schedule_work(&cons_data->co_flush_work);
+}
+
+static struct tty_driver *rm_cons_console_device(struct console *co, int *index)
+{
+	struct rm_cons_drv_data *cons_data = container_of(co, struct rm_cons_drv_data, console);
+	struct rm_cons_port *rm_port = co->data;
+
+	*index = rm_port->index;
+	return cons_data->tty_driver;
+}
+
+static int rm_cons_console_setup(struct console *co, char *unused)
+{
+	struct rm_cons_drv_data *cons_data = container_of(co, struct rm_cons_drv_data, console);
+	struct rm_cons_port *rm_port = co->data;
+	int ret;
+
+	if (!tty_port_get(&rm_port->port))
+		return -ENODEV;
+
+	cons_data->co_xmit_buf[0] = (unsigned char *)get_zeroed_page(GFP_KERNEL);
+	if (!cons_data->co_xmit_buf[0])
+		goto err;
+	cons_data->co_xmit_buf[1] = (unsigned char *)get_zeroed_page(GFP_KERNEL);
+	if (!cons_data->co_xmit_buf[1])
+		goto err;
+
+	mutex_lock(&rm_port->port.mutex);
+	if (!tty_port_initialized(&rm_port->port)) {
+		ret = gh_rm_console_open(rm_port->vmid);
+		if (ret) {
+			dev_err(rm_port->port.tty->dev, "Failed to open %s%d: %d\n",
+				co->name, rm_port->index, ret);
+			goto err;
+		}
+		tty_port_set_initialized(&rm_port->port, true);
+	}
+	rm_port->port.console = true;
+	mutex_unlock(&rm_port->port.mutex);
+
+	return 0;
+err:
+	if (cons_data->co_xmit_buf[1])
+		free_page((unsigned long)cons_data->co_xmit_buf[1]);
+	if (cons_data->co_xmit_buf[0])
+		free_page((unsigned long)cons_data->co_xmit_buf[0]);
+	mutex_unlock(&rm_port->port.mutex);
+	tty_port_put(&rm_port->port);
+	return ret;
+}
+
+static int rm_cons_console_exit(struct console *co)
+{
+	struct rm_cons_port *rm_port = co->data;
+	int ret;
+
+	mutex_lock(&rm_port->port.mutex);
+	rm_port->port.console = false;
+
+	if (!tty_port_active(&rm_port->port)) {
+		ret = gh_rm_console_close(rm_port->vmid);
+		if (ret)
+			dev_err(rm_port->port.tty->dev, "Failed to close %s%d: %d\n",
+				co->name, rm_port->index, ret);
+		tty_port_set_initialized(&rm_port->port, false);
+	}
+
+	mutex_unlock(&rm_port->port.mutex);
+	tty_port_put(&rm_port->port);
+
+	return 0;
+}
+
+static struct rm_cons_port *rm_cons_port_create(struct rm_cons_drv_data *cons_data, u16 vmid)
+{
+	struct rm_cons_port *rm_port;
+	struct device *ttydev;
+	unsigned int index;
+	int ret;
+
+	rm_port = kzalloc(sizeof(*rm_port), GFP_KERNEL);
+	if (!rm_port)
+		return ERR_PTR(-ENOMEM);
+	rm_port->vmid = vmid;
+	tty_port_init(&rm_port->port);
+	rm_port->port.ops = &rm_cons_port_ops;
+
+	spin_lock(&cons_data->ports_lock);
+	for (index = 0; index < RM_CONS_TTY_ADAPATERS; index++) {
+		if (!cons_data->ports[index]) {
+			cons_data->ports[index] = rm_port;
+			rm_port->index = index;
+			break;
+		}
+	}
+	spin_unlock(&cons_data->ports_lock);
+	if (index >= RM_CONS_TTY_ADAPATERS) {
+		ret = -ENOSPC;
+		goto err_put_port;
+	}
+
+	ttydev = tty_port_register_device_attr(&rm_port->port, cons_data->tty_driver, index,
+					      cons_data->dev, rm_port, NULL);
+	if (IS_ERR(ttydev)) {
+		ret = PTR_ERR(ttydev);
+		goto err_put_port;
+	}
+
+	return rm_port;
+err_put_port:
+	tty_port_put(&rm_port->port);
+	return ERR_PTR(ret);
+}
+
+static int rm_cons_console_probe(struct device *dev)
+{
+	struct rm_cons_drv_data *cons_data;
+	struct rm_cons_port *rm_port;
+	int ret;
+	u16 vmid;
+
+	cons_data = devm_kzalloc(dev, sizeof(*cons_data), GFP_KERNEL);
+	if (!cons_data)
+		return -ENOMEM;
+	dev_set_drvdata(dev, cons_data);
+	cons_data->dev = dev;
+
+	cons_data->tty_driver = tty_alloc_driver(RM_CONS_TTY_ADAPATERS,
+						 TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV |
+						 TTY_DRIVER_RESET_TERMIOS);
+	if (IS_ERR(cons_data->tty_driver))
+		return PTR_ERR(cons_data->tty_driver);
+
+	cons_data->tty_driver->driver_name = KBUILD_MODNAME;
+	cons_data->tty_driver->name = "ttyGH";
+	cons_data->tty_driver->type = TTY_DRIVER_TYPE_SYSTEM;
+	cons_data->tty_driver->subtype = SYSTEM_TYPE_TTY;
+	cons_data->tty_driver->init_termios = tty_std_termios;
+	tty_set_operations(cons_data->tty_driver, &rm_cons_tty_ops);
+
+	ret = tty_register_driver(cons_data->tty_driver);
+	if (ret) {
+		dev_err(dev, "Could not register tty driver: %d\n", ret);
+		goto err_put_tty;
+	}
+
+	spin_lock_init(&cons_data->ports_lock);
+
+	cons_data->rm_cons_notif.notifier_call = rm_cons_notif_handler;
+	ret = gh_rm_register_notifier(&cons_data->rm_cons_notif);
+	if (ret) {
+		dev_err(dev, "Could not register for resource manager notifications: %d\n", ret);
+		goto err_put_tty;
+	}
+
+	spin_lock_init(&cons_data->co_xmit_lock);
+	INIT_WORK(&cons_data->co_flush_work, rm_cons_console_flush_work);
+
+	rm_port = rm_cons_port_create(cons_data, GH_VMID_SELF);
+	if (IS_ERR(rm_port)) {
+		ret = PTR_ERR(rm_port);
+		dev_err(dev, "Could not create own console: %d\n", ret);
+		goto err_unreg_notif;
+	}
+
+	rm_port->port.console = 1;
+	strncpy(cons_data->console.name, "ttyGH", sizeof(cons_data->console.name));
+	cons_data->console.write = rm_cons_console_write;
+	cons_data->console.device = rm_cons_console_device;
+	cons_data->console.setup = rm_cons_console_setup;
+	cons_data->console.exit = rm_cons_console_exit;
+	cons_data->console.index = rm_port->index;
+	cons_data->console.data = rm_port;
+	register_console(&cons_data->console);
+
+	ret = gh_rm_get_vmid(&vmid);
+	if (!ret) {
+		rm_port = rm_cons_port_create(cons_data, vmid);
+		if (IS_ERR(rm_port))
+			dev_warn(dev, "Could not create loopback console: %ld\n", PTR_ERR(rm_port));
+	} else {
+		dev_warn(dev, "Failed to get this VM's VMID: %d. Not creating loop-back console\n",
+			 ret);
+	}
+
+	return 0;
+err_unreg_notif:
+	gh_rm_unregister_notifier(&cons_data->rm_cons_notif);
+err_put_tty:
+	tty_driver_kref_put(cons_data->tty_driver);
+	return ret;
+}
+
+static int rm_cons_console_remove(struct device *dev)
+{
+	struct rm_cons_drv_data *cons_data = dev_get_drvdata(dev);
+
+	unregister_console(&cons_data->console);
+	if (cons_data->co_xmit_buf[1])
+		free_page((unsigned long)cons_data->co_xmit_buf[1]);
+	if (cons_data->co_xmit_buf[0])
+		free_page((unsigned long)cons_data->co_xmit_buf[0]);
+	gh_rm_unregister_notifier(&cons_data->rm_cons_notif);
+	tty_unregister_driver(cons_data->tty_driver);
+	tty_driver_kref_put(cons_data->tty_driver);
+
+	return 0;
+}
+
+static struct gunyah_rm_cons_device_id rm_cons_console_ids[] = {
+	{ .name = GH_RM_DEVICE_CONSOLE },
+	{}
+};
+MODULE_DEVICE_TABLE(gunyah_rsc_mgr, rm_cons_console_ids);
+
+static struct gh_rm_driver rm_cons_console_drv = {
+	.drv = {
+		.name = KBUILD_MODNAME,
+		.probe = rm_cons_console_probe,
+		.remove = rm_cons_console_remove,
+	},
+	.id_table = rm_cons_console_ids,
+};
+module_gh_rm_driver(rm_cons_console_drv);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Gunyah Console");