powerpc/sysdev: implement FSL GTM support

GTM stands for General-purpose Timers Module and able to generate
timer{1,2,3,4} interrupts. These timers are used by the drivers that
need time precise interrupts (like for USB transactions scheduling for
the Freescale USB Host controller as found in some QE and CPM chips),
or these timers could be used as wakeup events from the CPU deep-sleep
mode.

Things unimplemented:
1. Cascaded (32 bit) timers (1-2, 3-4).
   This is straightforward to implement when needed, two timers should
   be marked as "requested" and configured as appropriate.
2. Super-cascaded (64 bit) timers (1-2-3-4).
   This is also straightforward to implement when needed, all timers
   should be marked as "requested" and configured as appropriate.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

1 files changed, 434 insertions, 0 deletions

diff --git a/arch/powerpc/sysdev/fsl_gtm.c b/arch/powerpc/sysdev/fsl_gtm.c
new file mode 100644
index 000000000000..714ec02fed2e
--- /dev/null
+++ b/arch/powerpc/sysdev/fsl_gtm.c
@@ -0,0 +1,434 @@
+/*
+ * Freescale General-purpose Timers Module
+ *
+ * Copyright (c) Freescale Semicondutor, Inc. 2006.
+ *               Shlomi Gridish <gridish@freescale.com>
+ *               Jerry Huang <Chang-Ming.Huang@freescale.com>
+ * Copyright (c) MontaVista Software, Inc. 2008.
+ *               Anton Vorontsov <avorontsov@ru.mvista.com>
+ *
+ * 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.
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/list.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/spinlock.h>
+#include <linux/bitops.h>
+#include <asm/fsl_gtm.h>
+
+#define GTCFR_STP(x)            ((x) & 1 ? 1 << 5 : 1 << 1)
+#define GTCFR_RST(x)            ((x) & 1 ? 1 << 4 : 1 << 0)
+
+#define GTMDR_ICLK_MASK         (3 << 1)
+#define GTMDR_ICLK_ICAS         (0 << 1)
+#define GTMDR_ICLK_ICLK         (1 << 1)
+#define GTMDR_ICLK_SLGO         (2 << 1)
+#define GTMDR_FRR               (1 << 3)
+#define GTMDR_ORI               (1 << 4)
+#define GTMDR_SPS(x)            ((x) << 8)
+
+struct gtm_timers_regs {
+        u8      gtcfr1;         /* Timer 1, Timer 2 global config register */
+        u8      res0[0x3];
+        u8      gtcfr2;         /* Timer 3, timer 4 global config register */
+        u8      res1[0xB];
+        __be16  gtmdr1;         /* Timer 1 mode register */
+        __be16  gtmdr2;         /* Timer 2 mode register */
+        __be16  gtrfr1;         /* Timer 1 reference register */
+        __be16  gtrfr2;         /* Timer 2 reference register */
+        __be16  gtcpr1;         /* Timer 1 capture register */
+        __be16  gtcpr2;         /* Timer 2 capture register */
+        __be16  gtcnr1;         /* Timer 1 counter */
+        __be16  gtcnr2;         /* Timer 2 counter */
+        __be16  gtmdr3;         /* Timer 3 mode register */
+        __be16  gtmdr4;         /* Timer 4 mode register */
+        __be16  gtrfr3;         /* Timer 3 reference register */
+        __be16  gtrfr4;         /* Timer 4 reference register */
+        __be16  gtcpr3;         /* Timer 3 capture register */
+        __be16  gtcpr4;         /* Timer 4 capture register */
+        __be16  gtcnr3;         /* Timer 3 counter */
+        __be16  gtcnr4;         /* Timer 4 counter */
+        __be16  gtevr1;         /* Timer 1 event register */
+        __be16  gtevr2;         /* Timer 2 event register */
+        __be16  gtevr3;         /* Timer 3 event register */
+        __be16  gtevr4;         /* Timer 4 event register */
+        __be16  gtpsr1;         /* Timer 1 prescale register */
+        __be16  gtpsr2;         /* Timer 2 prescale register */
+        __be16  gtpsr3;         /* Timer 3 prescale register */
+        __be16  gtpsr4;         /* Timer 4 prescale register */
+        u8 res2[0x40];
+} __attribute__ ((packed));
+
+struct gtm {
+        unsigned int clock;
+        struct gtm_timers_regs __iomem *regs;
+        struct gtm_timer timers[4];
+        spinlock_t lock;
+        struct list_head list_node;
+};
+
+static LIST_HEAD(gtms);
+
+/**
+ * gtm_get_timer - request GTM timer to use it with the rest of GTM API
+ * Context:     non-IRQ
+ *
+ * This function reserves GTM timer for later use. It returns gtm_timer
+ * structure to use with the rest of GTM API, you should use timer->irq
+ * to manage timer interrupt.
+ */
+struct gtm_timer *gtm_get_timer16(void)
+{
+        struct gtm *gtm = NULL;
+        int i;
+
+        list_for_each_entry(gtm, &gtms, list_node) {
+                spin_lock_irq(&gtm->lock);
+
+                for (i = 0; i < ARRAY_SIZE(gtm->timers); i++) {
+                        if (!gtm->timers[i].requested) {
+                                gtm->timers[i].requested = true;
+                                spin_unlock_irq(&gtm->lock);
+                                return &gtm->timers[i];
+                        }
+                }
+
+                spin_unlock_irq(&gtm->lock);
+        }
+
+        if (gtm)
+                return ERR_PTR(-EBUSY);
+        return ERR_PTR(-ENODEV);
+}
+EXPORT_SYMBOL(gtm_get_timer16);
+
+/**
+ * gtm_get_specific_timer - request specific GTM timer
+ * @gtm:        specific GTM, pass here GTM's device_node->data
+ * @timer:      specific timer number, Timer1 is 0.
+ * Context:     non-IRQ
+ *
+ * This function reserves GTM timer for later use. It returns gtm_timer
+ * structure to use with the rest of GTM API, you should use timer->irq
+ * to manage timer interrupt.
+ */
+struct gtm_timer *gtm_get_specific_timer16(struct gtm *gtm,
+                                           unsigned int timer)
+{
+        struct gtm_timer *ret = ERR_PTR(-EBUSY);
+
+        if (timer > 3)
+                return ERR_PTR(-EINVAL);
+
+        spin_lock_irq(&gtm->lock);
+
+        if (gtm->timers[timer].requested)
+                goto out;
+
+        ret = &gtm->timers[timer];
+        ret->requested = true;
+
+out:
+        spin_unlock_irq(&gtm->lock);
+        return ret;
+}
+EXPORT_SYMBOL(gtm_get_specific_timer16);
+
+/**
+ * gtm_put_timer16 - release 16 bits GTM timer
+ * @tmr:        pointer to the gtm_timer structure obtained from gtm_get_timer
+ * Context:     any
+ *
+ * This function releases GTM timer so others may request it.
+ */
+void gtm_put_timer16(struct gtm_timer *tmr)
+{
+        gtm_stop_timer16(tmr);
+
+        spin_lock_irq(&tmr->gtm->lock);
+        tmr->requested = false;
+        spin_unlock_irq(&tmr->gtm->lock);
+}
+EXPORT_SYMBOL(gtm_put_timer16);
+
+/*
+ * This is back-end for the exported functions, it's used to reset single
+ * timer in reference mode.
+ */
+static int gtm_set_ref_timer16(struct gtm_timer *tmr, int frequency,
+                               int reference_value, bool free_run)
+{
+        struct gtm *gtm = tmr->gtm;
+        int num = tmr - &gtm->timers[0];
+        unsigned int prescaler;
+        u8 iclk = GTMDR_ICLK_ICLK;
+        u8 psr;
+        u8 sps;
+        unsigned long flags;
+        int max_prescaler = 256 * 256 * 16;
+
+        /* CPM2 doesn't have primary prescaler */
+        if (!tmr->gtpsr)
+                max_prescaler /= 256;
+
+        prescaler = gtm->clock / frequency;
+        /*
+         * We have two 8 bit prescalers -- primary and secondary (psr, sps),
+         * plus "slow go" mode (clk / 16). So, total prescale value is
+         * 16 * (psr + 1) * (sps + 1). Though, for CPM2 GTMs we losing psr.
+         */
+        if (prescaler > max_prescaler)
+                return -EINVAL;
+
+        if (prescaler > max_prescaler / 16) {
+                iclk = GTMDR_ICLK_SLGO;
+                prescaler /= 16;
+        }
+
+        if (prescaler <= 256) {
+                psr = 0;
+                sps = prescaler - 1;
+        } else {
+                psr = 256 - 1;
+                sps = prescaler / 256 - 1;
+        }
+
+        spin_lock_irqsave(&gtm->lock, flags);
+
+        /*
+         * Properly reset timers: stop, reset, set up prescalers, reference
+         * value and clear event register.
+         */
+        clrsetbits_8(tmr->gtcfr, ~(GTCFR_STP(num) | GTCFR_RST(num)),
+                                 GTCFR_STP(num) | GTCFR_RST(num));
+
+        setbits8(tmr->gtcfr, GTCFR_STP(num));
+
+        if (tmr->gtpsr)
+                out_be16(tmr->gtpsr, psr);
+        clrsetbits_be16(tmr->gtmdr, 0xFFFF, iclk | GTMDR_SPS(sps) |
+                        GTMDR_ORI | (free_run ? GTMDR_FRR : 0));
+        out_be16(tmr->gtcnr, 0);
+        out_be16(tmr->gtrfr, reference_value);
+        out_be16(tmr->gtevr, 0xFFFF);
+
+        /* Let it be. */
+        clrbits8(tmr->gtcfr, GTCFR_STP(num));
+
+        spin_unlock_irqrestore(&gtm->lock, flags);
+
+        return 0;
+}
+
+/**
+ * gtm_set_timer16 - (re)set 16 bit timer with arbitrary precision
+ * @tmr:        pointer to the gtm_timer structure obtained from gtm_get_timer
+ * @usec:       timer interval in microseconds
+ * @reload:     if set, the timer will reset upon expiry rather than
+ *              continue running free.
+ * Context:     any
+ *
+ * This function (re)sets the GTM timer so that it counts up to the requested
+ * interval value, and fires the interrupt when the value is reached. This
+ * function will reduce the precision of the timer as needed in order for the
+ * requested timeout to fit in a 16-bit register.
+ */
+int gtm_set_timer16(struct gtm_timer *tmr, unsigned long usec, bool reload)
+{
+        /* quite obvious, frequency which is enough for µSec precision */
+        int freq = 1000000;
+        unsigned int bit;
+
+        bit = fls_long(usec);
+        if (bit > 15) {
+                freq >>= bit - 15;
+                usec >>= bit - 15;
+        }
+
+        if (!freq)
+                return -EINVAL;
+
+        return gtm_set_ref_timer16(tmr, freq, usec, reload);
+}
+EXPORT_SYMBOL(gtm_set_timer16);
+
+/**
+ * gtm_set_exact_utimer16 - (re)set 16 bits timer
+ * @tmr:        pointer to the gtm_timer structure obtained from gtm_get_timer
+ * @usec:       timer interval in microseconds
+ * @reload:     if set, the timer will reset upon expiry rather than
+ *              continue running free.
+ * Context:     any
+ *
+ * This function (re)sets GTM timer so that it counts up to the requested
+ * interval value, and fires the interrupt when the value is reached. If reload
+ * flag was set, timer will also reset itself upon reference value, otherwise
+ * it continues to increment.
+ *
+ * The _exact_ bit in the function name states that this function will not
+ * crop precision of the "usec" argument, thus usec is limited to 16 bits
+ * (single timer width).
+ */
+int gtm_set_exact_timer16(struct gtm_timer *tmr, u16 usec, bool reload)
+{
+        /* quite obvious, frequency which is enough for µSec precision */
+        const int freq = 1000000;
+
+        /*
+         * We can lower the frequency (and probably power consumption) by
+         * dividing both frequency and usec by 2 until there is no remainder.
+         * But we won't bother with this unless savings are measured, so just
+         * run the timer as is.
+         */
+
+        return gtm_set_ref_timer16(tmr, freq, usec, reload);
+}
+EXPORT_SYMBOL(gtm_set_exact_timer16);
+
+/**
+ * gtm_stop_timer16 - stop single timer
+ * @tmr:        pointer to the gtm_timer structure obtained from gtm_get_timer
+ * Context:     any
+ *
+ * This function simply stops the GTM timer.
+ */
+void gtm_stop_timer16(struct gtm_timer *tmr)
+{
+        struct gtm *gtm = tmr->gtm;
+        int num = tmr - &gtm->timers[0];
+        unsigned long flags;
+
+        spin_lock_irqsave(&gtm->lock, flags);
+
+        setbits8(tmr->gtcfr, GTCFR_STP(num));
+        out_be16(tmr->gtevr, 0xFFFF);
+
+        spin_unlock_irqrestore(&gtm->lock, flags);
+}
+EXPORT_SYMBOL(gtm_stop_timer16);
+
+/**
+ * gtm_ack_timer16 - acknowledge timer event (free-run timers only)
+ * @tmr:        pointer to the gtm_timer structure obtained from gtm_get_timer
+ * @events:     events mask to ack
+ * Context:     any
+ *
+ * Thus function used to acknowledge timer interrupt event, use it inside the
+ * interrupt handler.
+ */
+void gtm_ack_timer16(struct gtm_timer *tmr, u16 events)
+{
+        out_be16(tmr->gtevr, events);
+}
+EXPORT_SYMBOL(gtm_ack_timer16);
+
+static void __init gtm_set_shortcuts(struct device_node *np,
+                                     struct gtm_timer *timers,
+                                     struct gtm_timers_regs __iomem *regs)
+{
+        /*
+         * Yeah, I don't like this either, but timers' registers a bit messed,
+         * so we have to provide shortcuts to write timer independent code.
+         * Alternative option is to create gt*() accessors, but that will be
+         * even uglier and cryptic.
+         */
+        timers[0].gtcfr = &regs->gtcfr1;
+        timers[0].gtmdr = &regs->gtmdr1;
+        timers[0].gtcnr = &regs->gtcnr1;
+        timers[0].gtrfr = &regs->gtrfr1;
+        timers[0].gtevr = &regs->gtevr1;
+
+        timers[1].gtcfr = &regs->gtcfr1;
+        timers[1].gtmdr = &regs->gtmdr2;
+        timers[1].gtcnr = &regs->gtcnr2;
+        timers[1].gtrfr = &regs->gtrfr2;
+        timers[1].gtevr = &regs->gtevr2;
+
+        timers[2].gtcfr = &regs->gtcfr2;
+        timers[2].gtmdr = &regs->gtmdr3;
+        timers[2].gtcnr = &regs->gtcnr3;
+        timers[2].gtrfr = &regs->gtrfr3;
+        timers[2].gtevr = &regs->gtevr3;
+
+        timers[3].gtcfr = &regs->gtcfr2;
+        timers[3].gtmdr = &regs->gtmdr4;
+        timers[3].gtcnr = &regs->gtcnr4;
+        timers[3].gtrfr = &regs->gtrfr4;
+        timers[3].gtevr = &regs->gtevr4;
+
+        /* CPM2 doesn't have primary prescaler */
+        if (!of_device_is_compatible(np, "fsl,cpm2-gtm")) {
+                timers[0].gtpsr = &regs->gtpsr1;
+                timers[1].gtpsr = &regs->gtpsr2;
+                timers[2].gtpsr = &regs->gtpsr3;
+                timers[3].gtpsr = &regs->gtpsr4;
+        }
+}
+
+static int __init fsl_gtm_init(void)
+{
+        struct device_node *np;
+
+        for_each_compatible_node(np, NULL, "fsl,gtm") {
+                int i;
+                struct gtm *gtm;
+                const u32 *clock;
+                int size;
+
+                gtm = kzalloc(sizeof(*gtm), GFP_KERNEL);
+                if (!gtm) {
+                        pr_err("%s: unable to allocate memory\n",
+                                np->full_name);
+                        continue;
+                }
+
+                spin_lock_init(&gtm->lock);
+
+                clock = of_get_property(np, "clock-frequency", &size);
+                if (!clock || size != sizeof(*clock)) {
+                        pr_err("%s: no clock-frequency\n", np->full_name);
+                        goto err;
+                }
+                gtm->clock = *clock;
+
+                for (i = 0; i < ARRAY_SIZE(gtm->timers); i++) {
+                        int ret;
+                        struct resource irq;
+
+                        ret = of_irq_to_resource(np, i, &irq);
+                        if (ret == NO_IRQ) {
+                                pr_err("%s: not enough interrupts specified\n",
+                                       np->full_name);
+                                goto err;
+                        }
+                        gtm->timers[i].irq = irq.start;
+                        gtm->timers[i].gtm = gtm;
+                }
+
+                gtm->regs = of_iomap(np, 0);
+                if (!gtm->regs) {
+                        pr_err("%s: unable to iomap registers\n",
+                               np->full_name);
+                        goto err;
+                }
+
+                gtm_set_shortcuts(np, gtm->timers, gtm->regs);
+                list_add(&gtm->list_node, &gtms);
+
+                /* We don't want to lose the node and its ->data */
+                np->data = gtm;
+                of_node_get(np);
+
+                continue;
+err:
+                kfree(gtm);
+        }
+        return 0;
+}
+arch_initcall(fsl_gtm_init);