hvcs.c

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/*
 * IBM eServer Hypervisor Virtual Console Server Device Driver
 * Copyright (C) 2003, 2004 IBM Corp.
 *  Ryan S. Arnold ([e-mail])
 *
 *  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.
 *
 *  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., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 * Author(s) :  Ryan S. Arnold <[e-mail]>
 *
 * This is the device driver for the IBM Hypervisor Virtual Console Server,
 * "hvcs".  The IBM hvcs provides a tty driver interface to allow Linux
 * user space applications access to the system consoles of logically
 * partitioned operating systems, e.g. Linux, running on the same partitioned
 * Power5 ppc64 system.  Physical hardware consoles per partition are not
 * practical on this hardware so system consoles are accessed by this driver
 * using inter-partition firmware interfaces to virtual terminal devices.
 *
 * A vty is known to the HMC as a "virtual serial server adapter".  It is a
 * virtual terminal device that is created by firmware upon partition creation
 * to act as a partitioned OS's console device.
 *
 * Firmware dynamically (via hotplug) exposes vty-servers to a running ppc64
 * Linux system upon their creation by the HMC or their exposure during boot.
 * The non-user interactive backend of this driver is implemented as a vio
 * device driver so that it can receive notification of vty-server lifetimes
 * after it registers with the vio bus to handle vty-server probe and remove
 * callbacks.
 *
 * Many vty-servers can be configured to connect to one vty, but a vty can
 * only be actively connected to by a single vty-server, in any manner, at one
 * time.  If the HMC is currently hosting the console for a target Linux
 * partition; attempts to open the tty device to the partition's console using
 * the hvcs on any partition will return -EBUSY with every open attempt until
 * the HMC frees the connection between its vty-server and the desired
 * partition's vty device.  Conversely, a vty-server may only be connected to
 * a single vty at one time even though it may have several configured vty
 * partner possibilities.
 *
 * Firmware does not provide notification of vty partner changes to this
 * driver.  This means that an HMC Super Admin may add or remove partner vtys
 * from a vty-server's partner list but the changes will not be signaled to
 * the vty-server.  Firmware only notifies the driver when a vty-server is
 * added or removed from the system.  To compensate for this deficiency, this
 * driver implements a sysfs update attribute which provides a method for
 * rescanning partner information upon a user's request.
 *
 * Each vty-server, prior to being exposed to this driver is reference counted
 * using the 2.6 Linux kernel kobject construct.  This kobject is also used by
 * the vio bus to provide a vio device sysfs entry that this driver attaches
 * device specific attributes to, including partner information.  The vio bus
 * framework also provides a sysfs entry for each vio driver.  The hvcs driver
 * provides driver attributes in this entry.
 *
 * For direction on installation and usage of this driver please reference
 * Documentation/powerpc/hvcs.txt.
 */

#include <linux/device.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/kobject.h>
#include <linux/kthread.h>
#include <linux/list.h>
#include <linux/major.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/stat.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <asm/hvconsole.h>
#include <asm/hvcserver.h>
#include <asm/uaccess.h>
#include <asm/vio.h>

/*
 * 1.3.0 -> 1.3.1 In hvcs_open memset(..,0x00,..) instead of memset(..,0x3F,00).
 * Removed braces around single statements following conditionals.  Removed '=
 * 0' after static int declarations since these default to zero.  Removed
 * list_for_each_safe() and replaced with list_for_each_entry() in
 * hvcs_get_by_index().  The 'safe' version is un-needed now that the driver is
 * using spinlocks.  Changed spin_lock_irqsave() to spin_lock() when locking
 * hvcs_structs_lock and hvcs_pi_lock since these are not touched in an int
 * handler.  Initialized hvcs_structs_lock and hvcs_pi_lock to
 * SPIN_LOCK_UNLOCKED at declaration time rather than in hvcs_module_init().
 * Added spin_lock around list_del() in destroy_hvcs_struct() to protect the
 * list traversals from a deletion.  Removed '= NULL' from pointer declaration
 * statements since they are initialized NULL by default.  Removed wmb()
 * instances from hvcs_try_write().  They probably aren't needed with locking in
 * place.  Added check and cleanup for hvcs_pi_buff = kmalloc() in
 * hvcs_module_init().  Exposed hvcs_struct.index via a sysfs attribute so that
 * the coupling between /dev/hvcs* and a vty-server can be automatically
 * determined.  Moved kobject_put() in hvcs_open outside of the
 * spin_unlock_irqrestore().
 *
 * 1.3.1 -> 1.3.2 Changed method for determining hvcs_struct->index and had it
 * align with how the tty layer always assigns the lowest index available.  This
 * change resulted in a list of ints that denotes which indexes are available.
 * Device additions and removals use the new hvcs_get_index() and
 * hvcs_return_index() helper functions.  The list is created with
 * hvsc_alloc_index_list() and it is destroyed with hvcs_free_index_list().
 * Without these fixes hotplug vty-server adapter support goes crazy with this
 * driver if the user removes a vty-server adapter.  Moved free_irq() outside of
 * the hvcs_final_close() function in order to get it out of the spinlock.
 * Rearranged hvcs_close().  Cleaned up some printks and did some housekeeping
 * on the changelog.  Removed local CLC_LENGTH and used HVCS_CLC_LENGTH from
 * arch/ppc64/hvcserver.h.
 *
 * 1.3.2 -> 1.3.3 Replaced yield() in hvcs_close() with tty_wait_until_sent() to
 * prevent possible lockup with realtime scheduling as similarily pointed out by
 * akpm in hvc_console.  Changed resulted in the removal of hvcs_final_close()
 * to reorder cleanup operations and prevent discarding of pending data during
 * an hvcs_close().  Removed spinlock protection of hvcs_struct data members in
 * hvcs_write_room() and hvcs_chars_in_buffer() because they aren't needed.
 */

#define HVCS_DRIVER_VERSION "1.3.3"

MODULE_AUTHOR("Ryan S. Arnold <[e-mail]>");
MODULE_DESCRIPTION("IBM hvcs (Hypervisor Virtual Console Server) Driver");
MODULE_LICENSE("GPL");
MODULE_VERSION(HVCS_DRIVER_VERSION);

/*
 * Wait this long per iteration while trying to push buffered data to the
 * hypervisor before allowing the tty to complete a close operation.
 */
#define HVCS_CLOSE_WAIT (HZ/100) /* 1/10 of a second */

/*
 * Since the Linux TTY code does not currently (2-04-2004) support dynamic
 * addition of tty derived devices and we shouldn't allocate thousands of
 * tty_device pointers when the number of vty-server & vty partner connections
 * will most often be much lower than this, we'll arbitrarily allocate
 * HVCS_DEFAULT_SERVER_ADAPTERS tty_structs and cdev's by default when we
 * register the tty_driver. This can be overridden using an insmod parameter.
 */
#define HVCS_DEFAULT_SERVER_ADAPTERS	64

/*
 * The user can't insmod with more than HVCS_MAX_SERVER_ADAPTERS hvcs device
 * nodes as a sanity check.  Theoretically there can be over 1 Billion
 * vty-server & vty partner connections.
 */
#define HVCS_MAX_SERVER_ADAPTERS	1024

/*
 * We let Linux assign us a major number and we start the minors at zero.  There
 * is no intuitive mapping between minor number and the target vty-server
 * adapter except that each new vty-server adapter is always assigned to the
 * smallest minor number available.
 */
#define HVCS_MINOR_START	0

/*
 * The hcall interface involves putting 8 chars into each of two registers.
 * We load up those 2 registers (in arch/ppc64/hvconsole.c) by casting char[16]
 * to long[2].  It would work without __ALIGNED__, but a little (tiny) bit
 * slower because an unaligned load is slower than aligned load.
 */
#define __ALIGNED__	__attribute__((__aligned__(8)))

/*
 * How much data can firmware send with each hvc_put_chars()?  Maybe this
 * should be moved into an architecture specific area.
 */
#define HVCS_BUFF_LEN	16

/*
 * This is the maximum amount of data we'll let the user send us (hvcs_write) at
 * once in a chunk as a sanity check.
 */
#define HVCS_MAX_FROM_USER	4096

/*
 * Be careful when adding flags to this line discipline.  Don't add anything
 * that will cause echoing or we'll go into recursive loop echoing chars back
 * and forth with the console drivers.
 */
static struct termios hvcs_tty_termios = {
	.c_iflag = IGNBRK | IGNPAR,
	.c_oflag = OPOST,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_cc = INIT_C_CC
};

/*
 * This value is used to take the place of a command line parameter when the
 * module is inserted.  It starts as -1 and stays as such if the user doesn't
 * specify a module insmod parameter.  If they DO specify one then it is set to
 * the value of the integer passed in.
 */
static int hvcs_parm_num_devs = -1;
module_param(hvcs_parm_num_devs, int, 0);

char hvcs_driver_name[] = "hvcs";
char hvcs_device_node[] = "hvcs";
char hvcs_driver_string[]
	= "IBM hvcs (Hypervisor Virtual Console Server) Driver";

/* Status of partner info rescan triggered via sysfs. */
static int hvcs_rescan_status;

static struct tty_driver *hvcs_tty_driver;

/*
 * In order to be somewhat sane this driver always associates the hvcs_struct
 * index element with the numerically equal tty->index.  This means that a
 * hotplugged vty-server adapter will always map to the lowest index valued
 * device node.  If vty-servers were hotplug removed from the system and then
 * new ones added the new vty-server may have the largest slot number of all
 * the vty-server adapters in the partition but it may have the lowest dev node
 * index of all the adapters due to the hole left by the hotplug removed
 * adapter.  There are a set of functions provided to get the lowest index for
 * a new device as well as return the index to the list.  This list is allocated
 * with a number of elements equal to the number of device nodes requested when
 * the module was inserted.
 */
static int *hvcs_index_list;

/*
 * How large is the list?  This is kept for traversal since the list is
 * dynamically created.
 */
static int hvcs_index_count;

/*
 * Used by the khvcsd to pick up I/O operations when the kernel_thread is
 * already awake but potentially shifted to TASK_INTERRUPTIBLE state.
 */
static int hvcs_kicked;

/*
 * Use by the kthread construct for task operations like waking the sleeping
 * thread and stopping the kthread.
 */
static struct task_struct *hvcs_task;

/*
 * We allocate this for the use of all of the hvcs_structs when they fetch
 * partner info.
 */
static unsigned long *hvcs_pi_buff;

/* Only allow one hvcs_struct to use the hvcs_pi_buff at a time. */
static spinlock_t hvcs_pi_lock = SPIN_LOCK_UNLOCKED;

/* One vty-server per hvcs_struct */
struct hvcs_struct {
	spinlock_t lock;

	/*
	 * This index identifies this hvcs device as the complement to a
	 * specific tty index.
	 */
	unsigned int index;

	struct tty_struct *tty;
	unsigned int open_count;

	/*
	 * Used to tell the driver kernel_thread what operations need to take
	 * place upon this hvcs_struct instance.
	 */
	int todo_mask;

	/*
	 * This buffer is required so that when hvcs_write_room() reports that
	 * it can send HVCS_BUFF_LEN characters that it will buffer the full
	 * HVCS_BUFF_LEN characters if need be.  This is essential for opost
	 * writes since they do not do high level buffering and expect to be
	 * able to send what the driver commits to sending buffering
	 * [e.g. tab to space conversions in n_tty.c opost()].
	 */
	char buffer[HVCS_BUFF_LEN];
	int chars_in_buffer;

	/*
	 * Any variable below the kobject is valid before a tty is connected and
	 * stays valid after the tty is disconnected.  These shouldn't be
	 * whacked until the koject refcount reaches zero though some entries
	 * may be changed via sysfs initiatives.
	 */
	struct kobject kobj; /* ref count & hvcs_struct lifetime */
	int connected; /* is the vty-server currently connected to a vty? */
	uint32_t p_unit_address; /* partner unit address */
	uint32_t p_partition_ID; /* partner partition ID */
	char p_location_code[HVCS_CLC_LENGTH + 1]; /* CLC + Null Term */
	struct list_head next; /* list management */
	struct vio_dev *vdev;
};

/* Required to back map a kobject to its containing object */
#define from_kobj(kobj) container_of(kobj, struct hvcs_struct, kobj)

static struct list_head hvcs_structs = LIST_HEAD_INIT(hvcs_structs);
static spinlock_t hvcs_structs_lock = SPIN_LOCK_UNLOCKED;

static void hvcs_unthrottle(struct tty_struct *tty);
static void hvcs_throttle(struct tty_struct *tty);
static irqreturn_t hvcs_handle_interrupt(int irq, void *dev_instance,
		struct pt_regs *regs);

static int hvcs_write(struct tty_struct *tty, int from_user,
		const unsigned char *buf, int count);
static int hvcs_write_room(struct tty_struct *tty);
static int hvcs_chars_in_buffer(struct tty_struct *tty);

static int hvcs_has_pi(struct hvcs_struct *hvcsd);
static void hvcs_set_pi(struct hvcs_partner_info *pi,
		struct hvcs_struct *hvcsd);
static int hvcs_get_pi(struct hvcs_struct *hvcsd);
static int hvcs_rescan_devices_list(void);

static int hvcs_partner_connect(struct hvcs_struct *hvcsd);
static void hvcs_partner_free(struct hvcs_struct *hvcsd);

static int hvcs_enable_device(struct hvcs_struct *hvcsd,
		uint32_t unit_address, unsigned int irq, struct vio_dev *dev);

static void destroy_hvcs_struct(struct kobject *kobj);
static int hvcs_open(struct tty_struct *tty, struct file *filp);
static void hvcs_close(struct tty_struct *tty, struct file *filp);
static void hvcs_hangup(struct tty_struct * tty);

static void hvcs_create_device_attrs(struct hvcs_struct *hvcsd);
static void hvcs_remove_device_attrs(struct vio_dev *vdev);
static void hvcs_create_driver_attrs(void);
static void hvcs_remove_driver_attrs(void);

static int __devinit hvcs_probe(struct vio_dev *dev,
		const struct vio_device_id *id);
static int __devexit hvcs_remove(struct vio_dev *dev);
static int __init hvcs_module_init(void);
static void __exit hvcs_module_exit(void);

#define HVCS_SCHED_READ	0x00000001
#define HVCS_QUICK_READ	0x00000002
#define HVCS_TRY_WRITE	0x00000004
#define HVCS_READ_MASK	(HVCS_SCHED_READ | HVCS_QUICK_READ)

static void hvcs_kick(void)
{
	hvcs_kicked = 1;
	wmb();
	wake_up_process(hvcs_task);
}

static void hvcs_unthrottle(struct tty_struct *tty)
{
	struct hvcs_struct *hvcsd = tty->driver_data;
	unsigned long flags;

	spin_lock_irqsave(&hvcsd->lock, flags);
	hvcsd->todo_mask |= HVCS_SCHED_READ;
	spin_unlock_irqrestore(&hvcsd->lock, flags);
	hvcs_kick();
}

static void hvcs_throttle(struct tty_struct *tty)
{
	struct hvcs_struct *hvcsd = tty->driver_data;
	unsigned long flags;

	spin_lock_irqsave(&hvcsd->lock, flags);
	vio_disable_interrupts(hvcsd->vdev);
	spin_unlock_irqrestore(&hvcsd->lock, flags);
}

/*
 * If the device is being removed we don't have to worry about this interrupt
 * handler taking any further interrupts because they are disabled which means
 * the hvcs_struct will always be valid in this handler.
 */
static irqreturn_t hvcs_handle_interrupt(int irq, void *dev_instance,
		struct pt_regs *regs)
{
	struct hvcs_struct *hvcsd = dev_instance;

	spin_lock(&hvcsd->lock);
	vio_disable_interrupts(hvcsd->vdev);
	hvcsd->todo_mask |= HVCS_SCHED_READ;
	spin_unlock(&hvcsd->lock);
	hvcs_kick();

	return IRQ_HANDLED;
}

/* This function must be called with the hvcsd->lock held */
static void hvcs_try_write(struct hvcs_struct *hvcsd)
{
	uint32_t unit_address = hvcsd->vdev->unit_address;
	struct tty_struct *tty = hvcsd->tty;
	int sent;

	if (hvcsd->todo_mask & HVCS_TRY_WRITE) {
		/* won't send partial writes */
		sent = hvc_put_chars(unit_address,
				&hvcsd->buffer[0],
				hvcsd->chars_in_buffer );
		if (sent > 0) {
			hvcsd->chars_in_buffer = 0;
			/* wmb(); */