Contributors: 15
Author Tokens Token Proportion Commits Commit Proportion
Linus Torvalds (pre-git) 1690 48.68% 10 22.22%
Finn Thain 1281 36.90% 14 31.11%
Paul Mackerras 355 10.22% 5 11.11%
Benjamin Herrenschmidt 115 3.31% 2 4.44%
Anton Blanchard 10 0.29% 1 2.22%
Geert Uytterhoeven 7 0.20% 3 6.67%
Thomas Gleixner 4 0.12% 1 2.22%
Al Viro 3 0.09% 2 4.44%
Rob Herring 1 0.03% 1 2.22%
Jeremy Kerr 1 0.03% 1 2.22%
Alexey Dobriyan 1 0.03% 1 2.22%
Greg Kroah-Hartman 1 0.03% 1 2.22%
Michael Ellerman 1 0.03% 1 2.22%
Stephen Rothwell 1 0.03% 1 2.22%
Linus Torvalds 1 0.03% 1 2.22%
Total 3472 45 


// SPDX-License-Identifier: GPL-2.0
/*
 * Device driver for the Cuda and Egret system controllers found on PowerMacs
 * and 68k Macs.
 *
 * The Cuda or Egret is a 6805 microcontroller interfaced to the 6522 VIA.
 * This MCU controls system power, Parameter RAM, Real Time Clock and the
 * Apple Desktop Bus (ADB) that connects to the keyboard and mouse.
 *
 * Copyright (C) 1996 Paul Mackerras.
 */
#include <linux/stdarg.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/adb.h>
#include <linux/cuda.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#ifdef CONFIG_PPC
#include <asm/prom.h>
#include <asm/machdep.h>
#else
#include <asm/macintosh.h>
#include <asm/macints.h>
#include <asm/mac_via.h>
#endif
#include <asm/io.h>
#include <linux/init.h>

static volatile unsigned char __iomem *via;
static DEFINE_SPINLOCK(cuda_lock);

/* VIA registers - spaced 0x200 bytes apart */
#define RS		0x200		/* skip between registers */
#define B		0		/* B-side data */
#define A		RS		/* A-side data */
#define DIRB		(2*RS)		/* B-side direction (1=output) */
#define DIRA		(3*RS)		/* A-side direction (1=output) */
#define T1CL		(4*RS)		/* Timer 1 ctr/latch (low 8 bits) */
#define T1CH		(5*RS)		/* Timer 1 counter (high 8 bits) */
#define T1LL		(6*RS)		/* Timer 1 latch (low 8 bits) */
#define T1LH		(7*RS)		/* Timer 1 latch (high 8 bits) */
#define T2CL		(8*RS)		/* Timer 2 ctr/latch (low 8 bits) */
#define T2CH		(9*RS)		/* Timer 2 counter (high 8 bits) */
#define SR		(10*RS)		/* Shift register */
#define ACR		(11*RS)		/* Auxiliary control register */
#define PCR		(12*RS)		/* Peripheral control register */
#define IFR		(13*RS)		/* Interrupt flag register */
#define IER		(14*RS)		/* Interrupt enable register */
#define ANH		(15*RS)		/* A-side data, no handshake */

/*
 * When the Cuda design replaced the Egret, some signal names and
 * logic sense changed. They all serve the same purposes, however.
 *
 *   VIA pin       |  Egret pin
 * ----------------+------------------------------------------
 *   PB3 (input)   |  Transceiver session   (active low)
 *   PB4 (output)  |  VIA full              (active high)
 *   PB5 (output)  |  System session        (active high)
 *
 *   VIA pin       |  Cuda pin
 * ----------------+------------------------------------------
 *   PB3 (input)   |  Transfer request      (active low)
 *   PB4 (output)  |  Byte acknowledge      (active low)
 *   PB5 (output)  |  Transfer in progress  (active low)
 */

/* Bits in Port B data register */
#define TREQ		0x08		/* Transfer request */
#define TACK		0x10		/* Transfer acknowledge */
#define TIP		0x20		/* Transfer in progress */

/* Bits in ACR */
#define SR_CTRL		0x1c		/* Shift register control bits */
#define SR_EXT		0x0c		/* Shift on external clock */
#define SR_OUT		0x10		/* Shift out if 1 */

/* Bits in IFR and IER */
#define IER_SET		0x80		/* set bits in IER */
#define IER_CLR		0		/* clear bits in IER */
#define SR_INT		0x04		/* Shift register full/empty */

/* Duration of byte acknowledgement pulse (us) */
#define EGRET_TACK_ASSERTED_DELAY	300
#define EGRET_TACK_NEGATED_DELAY	400

/* Interval from interrupt to start of session (us) */
#define EGRET_SESSION_DELAY		450

#ifdef CONFIG_PPC
#define mcu_is_egret	false
#else
static bool mcu_is_egret;
#endif

static inline bool TREQ_asserted(u8 portb)
{
	return !(portb & TREQ);
}

static inline void assert_TIP(void)
{
	if (mcu_is_egret) {
		udelay(EGRET_SESSION_DELAY);
		out_8(&via[B], in_8(&via[B]) | TIP);
	} else
		out_8(&via[B], in_8(&via[B]) & ~TIP);
}

static inline void assert_TIP_and_TACK(void)
{
	if (mcu_is_egret) {
		udelay(EGRET_SESSION_DELAY);
		out_8(&via[B], in_8(&via[B]) | TIP | TACK);
	} else
		out_8(&via[B], in_8(&via[B]) & ~(TIP | TACK));
}

static inline void assert_TACK(void)
{
	if (mcu_is_egret) {
		udelay(EGRET_TACK_NEGATED_DELAY);
		out_8(&via[B], in_8(&via[B]) | TACK);
	} else
		out_8(&via[B], in_8(&via[B]) & ~TACK);
}

static inline void toggle_TACK(void)
{
	out_8(&via[B], in_8(&via[B]) ^ TACK);
}

static inline void negate_TACK(void)
{
	if (mcu_is_egret) {
		udelay(EGRET_TACK_ASSERTED_DELAY);
		out_8(&via[B], in_8(&via[B]) & ~TACK);
	} else
		out_8(&via[B], in_8(&via[B]) | TACK);
}

static inline void negate_TIP_and_TACK(void)
{
	if (mcu_is_egret) {
		udelay(EGRET_TACK_ASSERTED_DELAY);
		out_8(&via[B], in_8(&via[B]) & ~(TIP | TACK));
	} else
		out_8(&via[B], in_8(&via[B]) | TIP | TACK);
}

static enum cuda_state {
    idle,
    sent_first_byte,
    sending,
    reading,
    read_done,
    awaiting_reply
} cuda_state;

static struct adb_request *current_req;
static struct adb_request *last_req;
static unsigned char cuda_rbuf[16];
static unsigned char *reply_ptr;
static int reading_reply;
static int data_index;
static int cuda_irq;
#ifdef CONFIG_PPC
static struct device_node *vias;
#endif
static int cuda_fully_inited;

#ifdef CONFIG_ADB
static int cuda_probe(void);
static int cuda_send_request(struct adb_request *req, int sync);
static int cuda_adb_autopoll(int devs);
static int cuda_reset_adb_bus(void);
#endif /* CONFIG_ADB */

static int cuda_init_via(void);
static void cuda_start(void);
static irqreturn_t cuda_interrupt(int irq, void *arg);
static void cuda_input(unsigned char *buf, int nb);
void cuda_poll(void);
static int cuda_write(struct adb_request *req);

int cuda_request(struct adb_request *req,
		 void (*done)(struct adb_request *), int nbytes, ...);

#ifdef CONFIG_ADB
struct adb_driver via_cuda_driver = {
	.name         = "CUDA",
	.probe        = cuda_probe,
	.send_request = cuda_send_request,
	.autopoll     = cuda_adb_autopoll,
	.poll         = cuda_poll,
	.reset_bus    = cuda_reset_adb_bus,
};
#endif /* CONFIG_ADB */

#ifdef CONFIG_MAC
int __init find_via_cuda(void)
{
    struct adb_request req;
    int err;

    if (macintosh_config->adb_type != MAC_ADB_CUDA &&
        macintosh_config->adb_type != MAC_ADB_EGRET)
	return 0;

    via = via1;
    cuda_state = idle;
    mcu_is_egret = macintosh_config->adb_type == MAC_ADB_EGRET;

    err = cuda_init_via();
    if (err) {
	printk(KERN_ERR "cuda_init_via() failed\n");
	via = NULL;
	return 0;
    }

    /* enable autopoll */
    cuda_request(&req, NULL, 3, CUDA_PACKET, CUDA_AUTOPOLL, 1);
    while (!req.complete)
	cuda_poll();

    return 1;
}
#else
int __init find_via_cuda(void)
{
    struct adb_request req;
    phys_addr_t taddr;
    const u32 *reg;
    int err;

    if (vias != 0)
	return 1;
    vias = of_find_node_by_name(NULL, "via-cuda");
    if (vias == 0)
	return 0;

    reg = of_get_property(vias, "reg", NULL);
    if (reg == NULL) {
	    printk(KERN_ERR "via-cuda: No \"reg\" property !\n");
	    goto fail;
    }
    taddr = of_translate_address(vias, reg);
    if (taddr == 0) {
	    printk(KERN_ERR "via-cuda: Can't translate address !\n");
	    goto fail;
    }
    via = ioremap(taddr, 0x2000);
    if (via == NULL) {
	    printk(KERN_ERR "via-cuda: Can't map address !\n");
	    goto fail;
    }

    cuda_state = idle;
    sys_ctrler = SYS_CTRLER_CUDA;

    err = cuda_init_via();
    if (err) {
	printk(KERN_ERR "cuda_init_via() failed\n");
	via = NULL;
	return 0;
    }

    /* Clear and enable interrupts, but only on PPC. On 68K it's done  */
    /* for us by the main VIA driver in arch/m68k/mac/via.c        */

    out_8(&via[IFR], 0x7f);	/* clear interrupts by writing 1s */
    out_8(&via[IER], IER_SET|SR_INT); /* enable interrupt from SR */

    /* enable autopoll */
    cuda_request(&req, NULL, 3, CUDA_PACKET, CUDA_AUTOPOLL, 1);
    while (!req.complete)
	cuda_poll();

    return 1;

 fail:
    of_node_put(vias);
    vias = NULL;
    return 0;
}
#endif /* !defined CONFIG_MAC */

static int __init via_cuda_start(void)
{
    if (via == NULL)
	return -ENODEV;

#ifdef CONFIG_MAC
    cuda_irq = IRQ_MAC_ADB;
#else
    cuda_irq = irq_of_parse_and_map(vias, 0);
    if (!cuda_irq) {
	printk(KERN_ERR "via-cuda: can't map interrupts for %pOF\n",
	       vias);
	return -ENODEV;
    }
#endif

    if (request_irq(cuda_irq, cuda_interrupt, 0, "ADB", cuda_interrupt)) {
	printk(KERN_ERR "via-cuda: can't request irq %d\n", cuda_irq);
	return -EAGAIN;
    }

    pr_info("Macintosh Cuda and Egret driver.\n");

    cuda_fully_inited = 1;
    return 0;
}

device_initcall(via_cuda_start);

#ifdef CONFIG_ADB
static int
cuda_probe(void)
{
#ifdef CONFIG_PPC
    if (sys_ctrler != SYS_CTRLER_CUDA)
	return -ENODEV;
#else
    if (macintosh_config->adb_type != MAC_ADB_CUDA &&
        macintosh_config->adb_type != MAC_ADB_EGRET)
	return -ENODEV;
#endif
    if (via == NULL)
	return -ENODEV;
    return 0;
}
#endif /* CONFIG_ADB */

static int __init sync_egret(void)
{
	if (TREQ_asserted(in_8(&via[B]))) {
		/* Complete the inbound transfer */
		assert_TIP_and_TACK();
		while (1) {
			negate_TACK();
			mdelay(1);
			(void)in_8(&via[SR]);
			assert_TACK();
			if (!TREQ_asserted(in_8(&via[B])))
				break;
		}
		negate_TIP_and_TACK();
	} else if (in_8(&via[B]) & TIP) {
		/* Terminate the outbound transfer */
		negate_TACK();
		assert_TACK();
		mdelay(1);
		negate_TIP_and_TACK();
	}
	/* Clear shift register interrupt */
	if (in_8(&via[IFR]) & SR_INT)
		(void)in_8(&via[SR]);
	return 0;
}

#define WAIT_FOR(cond, what)					\
    do {                                                        \
    	int x;							\
	for (x = 1000; !(cond); --x) {				\
	    if (x == 0) {					\
		pr_err("Timeout waiting for " what "\n");	\
		return -ENXIO;					\
	    }							\
	    udelay(100);					\
	}							\
    } while (0)

static int
__init cuda_init_via(void)
{
#ifdef CONFIG_PPC
    out_8(&via[IER], 0x7f);					/* disable interrupts from VIA */
    (void)in_8(&via[IER]);
#else
    out_8(&via[IER], SR_INT);					/* disable SR interrupt from VIA */
#endif

    out_8(&via[DIRB], (in_8(&via[DIRB]) | TACK | TIP) & ~TREQ);	/* TACK & TIP out */
    out_8(&via[ACR], (in_8(&via[ACR]) & ~SR_CTRL) | SR_EXT);	/* SR data in */
    (void)in_8(&via[SR]);					/* clear any left-over data */

    if (mcu_is_egret)
	return sync_egret();

    negate_TIP_and_TACK();

    /* delay 4ms and then clear any pending interrupt */
    mdelay(4);
    (void)in_8(&via[SR]);
    out_8(&via[IFR], SR_INT);

    /* sync with the CUDA - assert TACK without TIP */
    assert_TACK();

    /* wait for the CUDA to assert TREQ in response */
    WAIT_FOR(TREQ_asserted(in_8(&via[B])), "CUDA response to sync");

    /* wait for the interrupt and then clear it */
    WAIT_FOR(in_8(&via[IFR]) & SR_INT, "CUDA response to sync (2)");
    (void)in_8(&via[SR]);
    out_8(&via[IFR], SR_INT);

    /* finish the sync by negating TACK */
    negate_TACK();

    /* wait for the CUDA to negate TREQ and the corresponding interrupt */
    WAIT_FOR(!TREQ_asserted(in_8(&via[B])), "CUDA response to sync (3)");
    WAIT_FOR(in_8(&via[IFR]) & SR_INT, "CUDA response to sync (4)");
    (void)in_8(&via[SR]);
    out_8(&via[IFR], SR_INT);

    return 0;
}

#ifdef CONFIG_ADB
/* Send an ADB command */
static int
cuda_send_request(struct adb_request *req, int sync)
{
    int i;

    if ((via == NULL) || !cuda_fully_inited) {
	req->complete = 1;
	return -ENXIO;
    }
  
    req->reply_expected = 1;

    i = cuda_write(req);
    if (i)
	return i;

    if (sync) {
	while (!req->complete)
	    cuda_poll();
    }
    return 0;
}


/* Enable/disable autopolling */
static int
cuda_adb_autopoll(int devs)
{
    struct adb_request req;

    if ((via == NULL) || !cuda_fully_inited)
	return -ENXIO;

    cuda_request(&req, NULL, 3, CUDA_PACKET, CUDA_AUTOPOLL, (devs? 1: 0));
    while (!req.complete)
	cuda_poll();
    return 0;
}

/* Reset adb bus - how do we do this?? */
static int
cuda_reset_adb_bus(void)
{
    struct adb_request req;

    if ((via == NULL) || !cuda_fully_inited)
	return -ENXIO;

    cuda_request(&req, NULL, 2, ADB_PACKET, 0);		/* maybe? */
    while (!req.complete)
	cuda_poll();
    return 0;
}
#endif /* CONFIG_ADB */

/* Construct and send a cuda request */
int
cuda_request(struct adb_request *req, void (*done)(struct adb_request *),
	     int nbytes, ...)
{
    va_list list;
    int i;

    if (via == NULL) {
	req->complete = 1;
	return -ENXIO;
    }

    req->nbytes = nbytes;
    req->done = done;
    va_start(list, nbytes);
    for (i = 0; i < nbytes; ++i)
	req->data[i] = va_arg(list, int);
    va_end(list);
    req->reply_expected = 1;
    return cuda_write(req);
}
EXPORT_SYMBOL(cuda_request);

static int
cuda_write(struct adb_request *req)
{
    unsigned long flags;

    if (req->nbytes < 2 || req->data[0] > CUDA_PACKET) {
	req->complete = 1;
	return -EINVAL;
    }
    req->next = NULL;
    req->sent = 0;
    req->complete = 0;
    req->reply_len = 0;

    spin_lock_irqsave(&cuda_lock, flags);
    if (current_req != 0) {
	last_req->next = req;
	last_req = req;
    } else {
	current_req = req;
	last_req = req;
	if (cuda_state == idle)
	    cuda_start();
    }
    spin_unlock_irqrestore(&cuda_lock, flags);

    return 0;
}

static void
cuda_start(void)
{
    /* assert cuda_state == idle */
    if (current_req == NULL)
	return;
    data_index = 0;
    if (TREQ_asserted(in_8(&via[B])))
	return;			/* a byte is coming in from the CUDA */

    /* set the shift register to shift out and send a byte */
    out_8(&via[ACR], in_8(&via[ACR]) | SR_OUT);
    out_8(&via[SR], current_req->data[data_index++]);
    if (mcu_is_egret)
	assert_TIP_and_TACK();
    else
	assert_TIP();
    cuda_state = sent_first_byte;
}

void
cuda_poll(void)
{
	cuda_interrupt(0, NULL);
}
EXPORT_SYMBOL(cuda_poll);

#define ARRAY_FULL(a, p)	((p) - (a) == ARRAY_SIZE(a))

static irqreturn_t
cuda_interrupt(int irq, void *arg)
{
    unsigned long flags;
    u8 status;
    struct adb_request *req = NULL;
    unsigned char ibuf[16];
    int ibuf_len = 0;
    int complete = 0;
    bool full;
    
    spin_lock_irqsave(&cuda_lock, flags);

    /* On powermacs, this handler is registered for the VIA IRQ. But they use
     * just the shift register IRQ -- other VIA interrupt sources are disabled.
     * On m68k macs, the VIA IRQ sources are dispatched individually. Unless
     * we are polling, the shift register IRQ flag has already been cleared.
     */

#ifdef CONFIG_MAC
    if (!arg)
#endif
    {
        if ((in_8(&via[IFR]) & SR_INT) == 0) {
            spin_unlock_irqrestore(&cuda_lock, flags);
            return IRQ_NONE;
        } else {
            out_8(&via[IFR], SR_INT);
        }
    }

    status = in_8(&via[B]) & (TIP | TACK | TREQ);

    switch (cuda_state) {
    case idle:
	/* System controller has unsolicited data for us */
	(void)in_8(&via[SR]);
idle_state:
	assert_TIP();
	cuda_state = reading;
	reply_ptr = cuda_rbuf;
	reading_reply = 0;
	break;

    case awaiting_reply:
	/* System controller has reply data for us */
	(void)in_8(&via[SR]);
	assert_TIP();
	cuda_state = reading;
	reply_ptr = current_req->reply;
	reading_reply = 1;
	break;

    case sent_first_byte:
	if (TREQ_asserted(status)) {
	    /* collision */
	    out_8(&via[ACR], in_8(&via[ACR]) & ~SR_OUT);
	    (void)in_8(&via[SR]);
	    negate_TIP_and_TACK();
	    cuda_state = idle;
	    /* Egret does not raise an "aborted" interrupt */
	    if (mcu_is_egret)
		goto idle_state;
	} else {
	    out_8(&via[SR], current_req->data[data_index++]);
	    toggle_TACK();
	    if (mcu_is_egret)
		assert_TACK();
	    cuda_state = sending;
	}
	break;

    case sending:
	req = current_req;
	if (data_index >= req->nbytes) {
	    out_8(&via[ACR], in_8(&via[ACR]) & ~SR_OUT);
	    (void)in_8(&via[SR]);
	    negate_TIP_and_TACK();
	    req->sent = 1;
	    if (req->reply_expected) {
		cuda_state = awaiting_reply;
	    } else {
		current_req = req->next;
		complete = 1;
		/* not sure about this */
		cuda_state = idle;
		cuda_start();
	    }
	} else {
	    out_8(&via[SR], req->data[data_index++]);
	    toggle_TACK();
	    if (mcu_is_egret)
		assert_TACK();
	}
	break;

    case reading:
	full = reading_reply ? ARRAY_FULL(current_req->reply, reply_ptr)
	                     : ARRAY_FULL(cuda_rbuf, reply_ptr);
	if (full)
	    (void)in_8(&via[SR]);
	else
	    *reply_ptr++ = in_8(&via[SR]);
	if (!TREQ_asserted(status) || full) {
	    if (mcu_is_egret)
		assert_TACK();
	    /* that's all folks */
	    negate_TIP_and_TACK();
	    cuda_state = read_done;
	    /* Egret does not raise a "read done" interrupt */
	    if (mcu_is_egret)
		goto read_done_state;
	} else {
	    toggle_TACK();
	    if (mcu_is_egret)
		negate_TACK();
	}
	break;

    case read_done:
	(void)in_8(&via[SR]);
read_done_state:
	if (reading_reply) {
	    req = current_req;
	    req->reply_len = reply_ptr - req->reply;
	    if (req->data[0] == ADB_PACKET) {
		/* Have to adjust the reply from ADB commands */
		if (req->reply_len <= 2 || (req->reply[1] & 2) != 0) {
		    /* the 0x2 bit indicates no response */
		    req->reply_len = 0;
		} else {
		    /* leave just the command and result bytes in the reply */
		    req->reply_len -= 2;
		    memmove(req->reply, req->reply + 2, req->reply_len);
		}
	    }
	    current_req = req->next;
	    complete = 1;
	    reading_reply = 0;
	} else {
	    /* This is tricky. We must break the spinlock to call
	     * cuda_input. However, doing so means we might get
	     * re-entered from another CPU getting an interrupt
	     * or calling cuda_poll(). I ended up using the stack
	     * (it's only for 16 bytes) and moving the actual
	     * call to cuda_input to outside of the lock.
	     */
	    ibuf_len = reply_ptr - cuda_rbuf;
	    memcpy(ibuf, cuda_rbuf, ibuf_len);
	}
	reply_ptr = cuda_rbuf;
	cuda_state = idle;
	cuda_start();
	if (cuda_state == idle && TREQ_asserted(in_8(&via[B]))) {
	    assert_TIP();
	    cuda_state = reading;
	}
	break;

    default:
	pr_err("cuda_interrupt: unknown cuda_state %d?\n", cuda_state);
    }
    spin_unlock_irqrestore(&cuda_lock, flags);
    if (complete && req) {
    	void (*done)(struct adb_request *) = req->done;
    	mb();
    	req->complete = 1;
    	/* Here, we assume that if the request has a done member, the
    	 * struct request will survive to setting req->complete to 1
    	 */
    	if (done)
		(*done)(req);
    }
    if (ibuf_len)
	cuda_input(ibuf, ibuf_len);
    return IRQ_HANDLED;
}

static void
cuda_input(unsigned char *buf, int nb)
{
    switch (buf[0]) {
    case ADB_PACKET:
#ifdef CONFIG_XMON
	if (nb == 5 && buf[2] == 0x2c) {
	    extern int xmon_wants_key, xmon_adb_keycode;
	    if (xmon_wants_key) {
		xmon_adb_keycode = buf[3];
		return;
	    }
	}
#endif /* CONFIG_XMON */
#ifdef CONFIG_ADB
	adb_input(buf+2, nb-2, buf[1] & 0x40);
#endif /* CONFIG_ADB */
	break;

    case TIMER_PACKET:
	/* Egret sends these periodically. Might be useful as a 'heartbeat'
	 * to trigger a recovery for the VIA shift register errata.
	 */
	break;

    default:
	print_hex_dump(KERN_INFO, "cuda_input: ", DUMP_PREFIX_NONE, 32, 1,
	               buf, nb, false);
    }
}

/* Offset between Unix time (1970-based) and Mac time (1904-based) */
#define RTC_OFFSET	2082844800

time64_t cuda_get_time(void)
{
	struct adb_request req;
	u32 now;

	if (cuda_request(&req, NULL, 2, CUDA_PACKET, CUDA_GET_TIME) < 0)
		return 0;
	while (!req.complete)
		cuda_poll();
	if (req.reply_len != 7)
		pr_err("%s: got %d byte reply\n", __func__, req.reply_len);
	now = (req.reply[3] << 24) + (req.reply[4] << 16) +
	      (req.reply[5] << 8) + req.reply[6];
	return (time64_t)now - RTC_OFFSET;
}

int cuda_set_rtc_time(struct rtc_time *tm)
{
	u32 now;
	struct adb_request req;

	now = lower_32_bits(rtc_tm_to_time64(tm) + RTC_OFFSET);
	if (cuda_request(&req, NULL, 6, CUDA_PACKET, CUDA_SET_TIME,
	                 now >> 24, now >> 16, now >> 8, now) < 0)
		return -ENXIO;
	while (!req.complete)
		cuda_poll();
	if ((req.reply_len != 3) && (req.reply_len != 7))
		pr_err("%s: got %d byte reply\n", __func__, req.reply_len);
	return 0;
}