[PATCH] W1: possible cleanups

[linux-2.6/verdex.git] / drivers / char / hw_random.c

/*
        Added support for the AMD Geode LX RNG
        (c) Copyright 2004-2005 Advanced Micro Devices, Inc.

        derived from

        Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG)
        (c) Copyright 2003 Red Hat Inc <jgarzik@redhat.com>
 
        derived from
 
        Hardware driver for the AMD 768 Random Number Generator (RNG)
        (c) Copyright 2001 Red Hat Inc <alan@redhat.com>

        derived from
 
        Hardware driver for Intel i810 Random Number Generator (RNG)
        Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com>
        Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com>

        Please read Documentation/hw_random.txt for details on use.

        ----------------------------------------------------------
        This software may be used and distributed according to the terms
        of the GNU General Public License, incorporated herein by reference.

 */


#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/pci.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/random.h>
#include <linux/miscdevice.h>
#include <linux/smp_lock.h>
#include <linux/mm.h>
#include <linux/delay.h>

#ifdef __i386__
#include <asm/msr.h>
#include <asm/cpufeature.h>
#endif

#include <asm/io.h>
#include <asm/uaccess.h>


/*
 * core module and version information
 */
#define RNG_VERSION "1.0.0"
#define RNG_MODULE_NAME "hw_random"
#define RNG_DRIVER_NAME   RNG_MODULE_NAME " hardware driver " RNG_VERSION
#define PFX RNG_MODULE_NAME ": "


/*
 * debugging macros
 */

/* pr_debug() collapses to a no-op if DEBUG is not defined */
#define DPRINTK(fmt, args...) pr_debug(PFX "%s: " fmt, __FUNCTION__ , ## args)


#undef RNG_NDEBUG        /* define to enable lightweight runtime checks */
#ifdef RNG_NDEBUG
#define assert(expr)                                                    \
                if(!(expr)) {                                           \
                printk(KERN_DEBUG PFX "Assertion failed! %s,%s,%s,"     \
                "line=%d\n", #expr, __FILE__, __FUNCTION__, __LINE__);  \
                }
#else
#define assert(expr)
#endif

#define RNG_MISCDEV_MINOR               183 /* official */

static int rng_dev_open (struct inode *inode, struct file *filp);
static ssize_t rng_dev_read (struct file *filp, char __user *buf, size_t size,
                                loff_t * offp);

static int __init intel_init (struct pci_dev *dev);
static void intel_cleanup(void);
static unsigned int intel_data_present (void);
static u32 intel_data_read (void);

static int __init amd_init (struct pci_dev *dev);
static void amd_cleanup(void);
static unsigned int amd_data_present (void);
static u32 amd_data_read (void);

#ifdef __i386__
static int __init via_init(struct pci_dev *dev);
static void via_cleanup(void);
static unsigned int via_data_present (void);
static u32 via_data_read (void);
#endif

static int __init geode_init(struct pci_dev *dev);
static void geode_cleanup(void);
static unsigned int geode_data_present (void);
static u32 geode_data_read (void);

struct rng_operations {
        int (*init) (struct pci_dev *dev);
        void (*cleanup) (void);
        unsigned int (*data_present) (void);
        u32 (*data_read) (void);
        unsigned int n_bytes; /* number of bytes per ->data_read */
};
static struct rng_operations *rng_ops;

static struct file_operations rng_chrdev_ops = {
        .owner          = THIS_MODULE,
        .open           = rng_dev_open,
        .read           = rng_dev_read,
};


static struct miscdevice rng_miscdev = {
        RNG_MISCDEV_MINOR,
        RNG_MODULE_NAME,
        &rng_chrdev_ops,
};

enum {
        rng_hw_none,
        rng_hw_intel,
        rng_hw_amd,
#ifdef __i386__
        rng_hw_via,
#endif
        rng_hw_geode,
};

static struct rng_operations rng_vendor_ops[] = {
        /* rng_hw_none */
        { },

        /* rng_hw_intel */
        { intel_init, intel_cleanup, intel_data_present,
          intel_data_read, 1 },

        /* rng_hw_amd */
        { amd_init, amd_cleanup, amd_data_present, amd_data_read, 4 },

#ifdef __i386__
        /* rng_hw_via */
        { via_init, via_cleanup, via_data_present, via_data_read, 1 },
#endif

        /* rng_hw_geode */
        { geode_init, geode_cleanup, geode_data_present, geode_data_read, 4 }
};

/*
 * Data for PCI driver interface
 *
 * This data only exists for exporting the supported
 * PCI ids via MODULE_DEVICE_TABLE.  We do not actually
 * register a pci_driver, because someone else might one day
 * want to register another driver on the same PCI id.
 */
static struct pci_device_id rng_pci_tbl[] = {
        { 0x1022, 0x7443, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_amd },
        { 0x1022, 0x746b, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_amd },

        { 0x8086, 0x2418, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_intel },
        { 0x8086, 0x2428, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_intel },
        { 0x8086, 0x2430, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_intel },
        { 0x8086, 0x2448, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_intel },
        { 0x8086, 0x244e, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_intel },
        { 0x8086, 0x245e, PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_intel },

        { PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_LX_AES,
          PCI_ANY_ID, PCI_ANY_ID, 0, 0, rng_hw_geode },

        { 0, }, /* terminate list */
};
MODULE_DEVICE_TABLE (pci, rng_pci_tbl);


/***********************************************************************
 *
 * Intel RNG operations
 *
 */

/*
 * RNG registers (offsets from rng_mem)
 */
#define INTEL_RNG_HW_STATUS                     0
#define         INTEL_RNG_PRESENT               0x40
#define         INTEL_RNG_ENABLED               0x01
#define INTEL_RNG_STATUS                        1
#define         INTEL_RNG_DATA_PRESENT          0x01
#define INTEL_RNG_DATA                          2

/*
 * Magic address at which Intel PCI bridges locate the RNG
 */
#define INTEL_RNG_ADDR                          0xFFBC015F
#define INTEL_RNG_ADDR_LEN                      3

/* token to our ioremap'd RNG register area */
static void __iomem *rng_mem;

static inline u8 intel_hwstatus (void)
{
        assert (rng_mem != NULL);
        return readb (rng_mem + INTEL_RNG_HW_STATUS);
}

static inline u8 intel_hwstatus_set (u8 hw_status)
{
        assert (rng_mem != NULL);
        writeb (hw_status, rng_mem + INTEL_RNG_HW_STATUS);
        return intel_hwstatus ();
}

static unsigned int intel_data_present(void)
{
        assert (rng_mem != NULL);

        return (readb (rng_mem + INTEL_RNG_STATUS) & INTEL_RNG_DATA_PRESENT) ?
                1 : 0;
}

static u32 intel_data_read(void)
{
        assert (rng_mem != NULL);

        return readb (rng_mem + INTEL_RNG_DATA);
}

static int __init intel_init (struct pci_dev *dev)
{
        int rc;
        u8 hw_status;

        DPRINTK ("ENTER\n");

        rng_mem = ioremap (INTEL_RNG_ADDR, INTEL_RNG_ADDR_LEN);
        if (rng_mem == NULL) {
                printk (KERN_ERR PFX "cannot ioremap RNG Memory\n");
                rc = -EBUSY;
                goto err_out;
        }

        /* Check for Intel 82802 */
        hw_status = intel_hwstatus ();
        if ((hw_status & INTEL_RNG_PRESENT) == 0) {
                printk (KERN_ERR PFX "RNG not detected\n");
                rc = -ENODEV;
                goto err_out_free_map;
        }

        /* turn RNG h/w on, if it's off */
        if ((hw_status & INTEL_RNG_ENABLED) == 0)
                hw_status = intel_hwstatus_set (hw_status | INTEL_RNG_ENABLED);
        if ((hw_status & INTEL_RNG_ENABLED) == 0) {
                printk (KERN_ERR PFX "cannot enable RNG, aborting\n");
                rc = -EIO;
                goto err_out_free_map;
        }

        DPRINTK ("EXIT, returning 0\n");
        return 0;

err_out_free_map:
        iounmap (rng_mem);
        rng_mem = NULL;
err_out:
        DPRINTK ("EXIT, returning %d\n", rc);
        return rc;
}

static void intel_cleanup(void)
{
        u8 hw_status;

        hw_status = intel_hwstatus ();
        if (hw_status & INTEL_RNG_ENABLED)
                intel_hwstatus_set (hw_status & ~INTEL_RNG_ENABLED);
        else
                printk(KERN_WARNING PFX "unusual: RNG already disabled\n");
        iounmap(rng_mem);
        rng_mem = NULL;
}

/***********************************************************************
 *
 * AMD RNG operations
 *
 */

static u32 pmbase;                      /* PMxx I/O base */
static struct pci_dev *amd_dev;

static unsigned int amd_data_present (void)
{
        return inl(pmbase + 0xF4) & 1;
}


static u32 amd_data_read (void)
{
        return inl(pmbase + 0xF0);
}

static int __init amd_init (struct pci_dev *dev)
{
        int rc;
        u8 rnen;

        DPRINTK ("ENTER\n");

        pci_read_config_dword(dev, 0x58, &pmbase);

        pmbase &= 0x0000FF00;

        if (pmbase == 0)
        {
                printk (KERN_ERR PFX "power management base not set\n");
                rc = -EIO;
                goto err_out;
        }

        pci_read_config_byte(dev, 0x40, &rnen);
        rnen |= (1 << 7);       /* RNG on */
        pci_write_config_byte(dev, 0x40, rnen);

        pci_read_config_byte(dev, 0x41, &rnen);
        rnen |= (1 << 7);       /* PMIO enable */
        pci_write_config_byte(dev, 0x41, rnen);

        pr_info( PFX "AMD768 system management I/O registers at 0x%X.\n",
                        pmbase);

        amd_dev = dev;

        DPRINTK ("EXIT, returning 0\n");
        return 0;

err_out:
        DPRINTK ("EXIT, returning %d\n", rc);
        return rc;
}

static void amd_cleanup(void)
{
        u8 rnen;

        pci_read_config_byte(amd_dev, 0x40, &rnen);
        rnen &= ~(1 << 7);      /* RNG off */
        pci_write_config_byte(amd_dev, 0x40, rnen);

        /* FIXME: twiddle pmio, also? */
}

#ifdef __i386__
/***********************************************************************
 *
 * VIA RNG operations
 *
 */

enum {
        VIA_STRFILT_CNT_SHIFT   = 16,
        VIA_STRFILT_FAIL        = (1 << 15),
        VIA_STRFILT_ENABLE      = (1 << 14),
        VIA_RAWBITS_ENABLE      = (1 << 13),
        VIA_RNG_ENABLE          = (1 << 6),
        VIA_XSTORE_CNT_MASK     = 0x0F,

        VIA_RNG_CHUNK_8         = 0x00, /* 64 rand bits, 64 stored bits */
        VIA_RNG_CHUNK_4         = 0x01, /* 32 rand bits, 32 stored bits */
        VIA_RNG_CHUNK_4_MASK    = 0xFFFFFFFF,
        VIA_RNG_CHUNK_2         = 0x02, /* 16 rand bits, 32 stored bits */
        VIA_RNG_CHUNK_2_MASK    = 0xFFFF,
        VIA_RNG_CHUNK_1         = 0x03, /* 8 rand bits, 32 stored bits */
        VIA_RNG_CHUNK_1_MASK    = 0xFF,
};

static u32 via_rng_datum;

/*
 * Investigate using the 'rep' prefix to obtain 32 bits of random data
 * in one insn.  The upside is potentially better performance.  The
 * downside is that the instruction becomes no longer atomic.  Due to
 * this, just like familiar issues with /dev/random itself, the worst
 * case of a 'rep xstore' could potentially pause a cpu for an
 * unreasonably long time.  In practice, this condition would likely
 * only occur when the hardware is failing.  (or so we hope :))
 *
 * Another possible performance boost may come from simply buffering
 * until we have 4 bytes, thus returning a u32 at a time,
 * instead of the current u8-at-a-time.
 */

static inline u32 xstore(u32 *addr, u32 edx_in)
{
        u32 eax_out;

        asm(".byte 0x0F,0xA7,0xC0 /* xstore %%edi (addr=%0) */"
                :"=m"(*addr), "=a"(eax_out)
                :"D"(addr), "d"(edx_in));

        return eax_out;
}

static unsigned int via_data_present(void)
{
        u32 bytes_out;

        /* We choose the recommended 1-byte-per-instruction RNG rate,
         * for greater randomness at the expense of speed.  Larger
         * values 2, 4, or 8 bytes-per-instruction yield greater
         * speed at lesser randomness.
         *
         * If you change this to another VIA_CHUNK_n, you must also
         * change the ->n_bytes values in rng_vendor_ops[] tables.
         * VIA_CHUNK_8 requires further code changes.
         *
         * A copy of MSR_VIA_RNG is placed in eax_out when xstore
         * completes.
         */
        via_rng_datum = 0; /* paranoia, not really necessary */
        bytes_out = xstore(&via_rng_datum, VIA_RNG_CHUNK_1) & VIA_XSTORE_CNT_MASK;
        if (bytes_out == 0)
                return 0;

        return 1;
}

static u32 via_data_read(void)
{
        return via_rng_datum;
}

static int __init via_init(struct pci_dev *dev)
{
        u32 lo, hi, old_lo;

        /* Control the RNG via MSR.  Tread lightly and pay very close
         * close attention to values written, as the reserved fields
         * are documented to be "undefined and unpredictable"; but it
         * does not say to write them as zero, so I make a guess that
         * we restore the values we find in the register.
         */
        rdmsr(MSR_VIA_RNG, lo, hi);

        old_lo = lo;
        lo &= ~(0x7f << VIA_STRFILT_CNT_SHIFT);
        lo &= ~VIA_XSTORE_CNT_MASK;
        lo &= ~(VIA_STRFILT_ENABLE | VIA_STRFILT_FAIL | VIA_RAWBITS_ENABLE);
        lo |= VIA_RNG_ENABLE;

        if (lo != old_lo)
                wrmsr(MSR_VIA_RNG, lo, hi);

        /* perhaps-unnecessary sanity check; remove after testing if
           unneeded */
        rdmsr(MSR_VIA_RNG, lo, hi);
        if ((lo & VIA_RNG_ENABLE) == 0) {
                printk(KERN_ERR PFX "cannot enable VIA C3 RNG, aborting\n");
                return -ENODEV;
        }

        return 0;
}

static void via_cleanup(void)
{
        /* do nothing */
}
#endif

/***********************************************************************
 *
 * AMD Geode RNG operations
 *
 */

static void __iomem *geode_rng_base = NULL;

#define GEODE_RNG_DATA_REG   0x50
#define GEODE_RNG_STATUS_REG 0x54

static u32 geode_data_read(void)
{
        u32 val;

        assert(geode_rng_base != NULL);
        val = readl(geode_rng_base + GEODE_RNG_DATA_REG);
        return val;
}

static unsigned int geode_data_present(void)
{
        u32 val;

        assert(geode_rng_base != NULL);
        val = readl(geode_rng_base + GEODE_RNG_STATUS_REG);
        return val;
}

static void geode_cleanup(void)
{
        iounmap(geode_rng_base);
        geode_rng_base = NULL;
}

static int geode_init(struct pci_dev *dev)
{
        unsigned long rng_base = pci_resource_start(dev, 0);

        if (rng_base == 0)
                return 1;

        geode_rng_base = ioremap(rng_base, 0x58);

        if (geode_rng_base == NULL) {
                printk(KERN_ERR PFX "Cannot ioremap RNG memory\n");
                return -EBUSY;
        }

        return 0;
}

/***********************************************************************
 *
 * /dev/hwrandom character device handling (major 10, minor 183)
 *
 */

static int rng_dev_open (struct inode *inode, struct file *filp)
{
        /* enforce read-only access to this chrdev */
        if ((filp->f_mode & FMODE_READ) == 0)
                return -EINVAL;
        if (filp->f_mode & FMODE_WRITE)
                return -EINVAL;

        return 0;
}


static ssize_t rng_dev_read (struct file *filp, char __user *buf, size_t size,
                                loff_t * offp)
{
        static DEFINE_SPINLOCK(rng_lock);
        unsigned int have_data;
        u32 data = 0;
        ssize_t ret = 0;

        while (size) {
                spin_lock(&rng_lock);

                have_data = 0;
                if (rng_ops->data_present()) {
                        data = rng_ops->data_read();
                        have_data = rng_ops->n_bytes;
                }

                spin_unlock (&rng_lock);

                while (have_data && size) {
                        if (put_user((u8)data, buf++)) {
                                ret = ret ? : -EFAULT;
                                break;
                        }
                        size--;
                        ret++;
                        have_data--;
                        data>>=8;
                }

                if (filp->f_flags & O_NONBLOCK)
                        return ret ? : -EAGAIN;

                if(need_resched())
                        schedule_timeout_interruptible(1);
                else
                        udelay(200);    /* FIXME: We could poll for 250uS ?? */

                if (signal_pending (current))
                        return ret ? : -ERESTARTSYS;
        }
        return ret;
}



/*
 * rng_init_one - look for and attempt to init a single RNG
 */
static int __init rng_init_one (struct pci_dev *dev)
{
        int rc;

        DPRINTK ("ENTER\n");

        assert(rng_ops != NULL);

        rc = rng_ops->init(dev);
        if (rc)
                goto err_out;

        rc = misc_register (&rng_miscdev);
        if (rc) {
                printk (KERN_ERR PFX "misc device register failed\n");
                goto err_out_cleanup_hw;
        }

        DPRINTK ("EXIT, returning 0\n");
        return 0;

err_out_cleanup_hw:
        rng_ops->cleanup();
err_out:
        DPRINTK ("EXIT, returning %d\n", rc);
        return rc;
}



MODULE_AUTHOR("The Linux Kernel team");
MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
MODULE_LICENSE("GPL");


/*
 * rng_init - initialize RNG module
 */
static int __init rng_init (void)
{
        int rc;
        struct pci_dev *pdev = NULL;
        const struct pci_device_id *ent;

        DPRINTK ("ENTER\n");

        /* Probe for Intel, AMD, Geode RNGs */
        for_each_pci_dev(pdev) {
                ent = pci_match_id(rng_pci_tbl, pdev);
                if (ent) {
                        rng_ops = &rng_vendor_ops[ent->driver_data];
                        goto match;
                }
        }

#ifdef __i386__
        /* Probe for VIA RNG */
        if (cpu_has_xstore) {
                rng_ops = &rng_vendor_ops[rng_hw_via];
                pdev = NULL;
                goto match;
        }
#endif

        DPRINTK ("EXIT, returning -ENODEV\n");
        return -ENODEV;

match:
        rc = rng_init_one (pdev);
        if (rc)
                return rc;

        pr_info( RNG_DRIVER_NAME " loaded\n");

        DPRINTK ("EXIT, returning 0\n");
        return 0;
}


/*
 * rng_init - shutdown RNG module
 */
static void __exit rng_cleanup (void)
{
        DPRINTK ("ENTER\n");

        misc_deregister (&rng_miscdev);

        if (rng_ops->cleanup)
                rng_ops->cleanup();

        DPRINTK ("EXIT\n");
}


module_init (rng_init);
module_exit (rng_cleanup);