/* ChibiOS - Copyright (C) 2006..2016 Giovanni Di Sirio Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. */ #include #include "ch.h" #include "hal.h" /*===========================================================================*/ /* SPI driver related. */ /*===========================================================================*/ #define SPI_LOOPBACK /* * Maximum speed SPI configuration (27MHz, CPHA=0, CPOL=0, MSb first). */ static const SPIConfig hs_spicfg = { NULL, GPIOB, GPIOB_ARD_D15, SPI_CR1_BR_0, SPI_CR2_DS_2 | SPI_CR2_DS_1 | SPI_CR2_DS_0 }; /* * Low speed SPI configuration (421.875kHz, CPHA=0, CPOL=0, MSb first). */ static const SPIConfig ls_spicfg = { NULL, GPIOB, GPIOB_ARD_D14, SPI_CR1_BR_2 | SPI_CR1_BR_1, SPI_CR2_DS_2 | SPI_CR2_DS_1 | SPI_CR2_DS_0 }; /* * SPI TX and RX buffers. * Note, the buffer are aligned to a 32 bytes boundary because limitations * imposed by the data cache. Note, this is GNU specific, it must be * handled differently for other compilers. */ #define SPI_BUFFERS_SIZE 128U static uint8_t txbuf[SPI_BUFFERS_SIZE]; static uint8_t rxbuf[SPI_BUFFERS_SIZE]; /*===========================================================================*/ /* Application code. */ /*===========================================================================*/ /* * SPI bus contender 1. */ static THD_WORKING_AREA(spi_thread_1_wa, 256); static THD_FUNCTION(spi_thread_1, p) { (void)p; chRegSetThreadName("SPI thread 1"); while (true) { unsigned i; /* Bush acquisition and SPI reprogramming.*/ spiAcquireBus(&SPID2); spiStart(&SPID2, &hs_spicfg); /* Preparing data buffer and flushing cache.*/ for (i = 0; i < SPI_BUFFERS_SIZE; i++) txbuf[i] = (uint8_t)i; /* Slave selection and data exchange.*/ spiSelect(&SPID2); spiExchange(&SPID2, SPI_BUFFERS_SIZE, txbuf, rxbuf); spiUnselect(&SPID2); #if defined(SPI_LOOPBACK) if (memcmp(txbuf, rxbuf, SPI_BUFFERS_SIZE) != 0) chSysHalt("loopback failure"); #endif /* Releasing the bus.*/ spiReleaseBus(&SPID2); } } /* * SPI bus contender 2. */ static THD_WORKING_AREA(spi_thread_2_wa, 256); static THD_FUNCTION(spi_thread_2, p) { (void)p; chRegSetThreadName("SPI thread 2"); while (true) { unsigned i; /* Bush acquisition and SPI reprogramming.*/ spiAcquireBus(&SPID2); spiStart(&SPID2, &ls_spicfg); /* Preparing data buffer and flushing cache.*/ for (i = 0; i < SPI_BUFFERS_SIZE; i++) txbuf[i] = (uint8_t)(128U + i); /* Slave selection and data exchange.*/ spiSelect(&SPID2); spiExchange(&SPID2, SPI_BUFFERS_SIZE, txbuf, rxbuf); spiUnselect(&SPID2); #if defined(SPI_LOOPBACK) if (memcmp(txbuf, rxbuf, SPI_BUFFERS_SIZE) != 0) chSysHalt("loopback failure"); #endif /* Releasing the bus.*/ spiReleaseBus(&SPID2); } } /* * Application entry point. */ int main(void) { /* * System initializations. * - HAL initialization, this also initializes the configured device drivers * and performs the board-specific initializations. * - Kernel initialization, the main() function becomes a thread and the * RTOS is active. */ halInit(); chSysInit(); /* * SPI2 I/O pins setup. */ palSetLineMode(LINE_ARD_D13, PAL_MODE_ALTERNATE(5) | PAL_STM32_OSPEED_HIGHEST); /* SPI SCK. */ palSetLineMode(LINE_ARD_D12, PAL_MODE_ALTERNATE(5) | PAL_STM32_OSPEED_HIGHEST); /* MISO. */ palSetLineMode(LINE_ARD_D11, PAL_MODE_ALTERNATE(5) | PAL_STM32_OSPEED_HIGHEST); /* MOSI. */ palSetLine(LINE_ARD_D15); palSetLineMode(LINE_ARD_D15, PAL_MODE_OUTPUT_PUSHPULL); /* CS0. */ palSetLine(LINE_ARD_D14); palSetLineMode(LINE_ARD_D14, PAL_MODE_OUTPUT_PUSHPULL); /* CS1. */ /* * Starting the transmitter and receiver threads. */ chThdCreateStatic(spi_thread_1_wa, sizeof(spi_thread_1_wa), NORMALPRIO + 1, spi_thread_1, NULL); chThdCreateStatic(spi_thread_2_wa, sizeof(spi_thread_2_wa), NORMALPRIO + 1, spi_thread_2, NULL); /* * Normal main() thread activity, in this demo it does nothing. */ while (true) { chThdSleepMilliseconds(500); } } href='#n47'>47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 
/*
 * cpuidle_menu - menu governor for cpu idle, main idea come from Linux.
 *            drivers/cpuidle/governors/menu.c 
 *
 *  Copyright (C) 2006-2007 Adam Belay <abelay@novell.com>
 *  Copyright (C) 2007, 2008 Intel Corporation
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 *  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.
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 */
#include <xen/config.h>
#include <xen/errno.h>
#include <xen/lib.h>
#include <xen/types.h>
#include <xen/acpi.h>
#include <xen/timer.h>
#include <xen/cpuidle.h>
#include <asm/irq.h>

#define BUCKETS 6
#define RESOLUTION 1024
#define DECAY 4
#define MAX_INTERESTING 50000

/*
 * Concepts and ideas behind the menu governor
 *
 * For the menu governor, there are 3 decision factors for picking a C
 * state:
 * 1) Energy break even point
 * 2) Performance impact
 * 3) Latency tolerance (TBD: from guest virtual C state)
 * These these three factors are treated independently.
 *
 * Energy break even point
 * -----------------------
 * C state entry and exit have an energy cost, and a certain amount of time in
 * the  C state is required to actually break even on this cost. CPUIDLE
 * provides us this duration in the "target_residency" field. So all that we
 * need is a good prediction of how long we'll be idle. Like the traditional
 * menu governor, we start with the actual known "next timer event" time.
 *
 * Since there are other source of wakeups (interrupts for example) than
 * the next timer event, this estimation is rather optimistic. To get a
 * more realistic estimate, a correction factor is applied to the estimate,
 * that is based on historic behavior. For example, if in the past the actual
 * duration always was 50% of the next timer tick, the correction factor will
 * be 0.5.
 *
 * menu uses a running average for this correction factor, however it uses a
 * set of factors, not just a single factor. This stems from the realization
 * that the ratio is dependent on the order of magnitude of the expected
 * duration; if we expect 500 milliseconds of idle time the likelihood of
 * getting an interrupt very early is much higher than if we expect 50 micro
 * seconds of idle time.
 * For this reason we keep an array of 6 independent factors, that gets
 * indexed based on the magnitude of the expected duration
 *
 * Limiting Performance Impact
 * ---------------------------
 * C states, especially those with large exit latencies, can have a real
 * noticable impact on workloads, which is not acceptable for most sysadmins,
 * and in addition, less performance has a power price of its own.
 *
 * As a general rule of thumb, menu assumes that the following heuristic
 * holds:
 *     The busier the system, the less impact of C states is acceptable
 *
 * This rule-of-thumb is implemented using average interrupt interval:
 * If the exit latency times multiplier is longer than the average
 * interrupt interval, the C state is not considered a candidate
 * for selection due to a too high performance impact. So the smaller
 * the average interrupt interval is, the smaller C state latency should be
 * and thus the less likely a busy CPU will hit such a deep C state.
 *
 */

struct perf_factor{
    s_time_t    time_stamp;
    s_time_t    duration;
    unsigned int irq_count_stamp;
    unsigned int irq_sum;
};

struct menu_device
{
    int             last_state_idx;
    unsigned int    expected_us;
    u64             predicted_us;
    unsigned int    measured_us;
    unsigned int    exit_us;
    unsigned int    bucket;
    u64             correction_factor[BUCKETS];
    struct perf_factor pf;
};

static DEFINE_PER_CPU(struct menu_device, menu_devices);

static inline int which_bucket(unsigned int duration)
{
   int bucket = 0;

   if (duration < 10)
       return bucket;
   if (duration < 100)
       return bucket + 1;
   if (duration < 1000)
       return bucket + 2;
   if (duration < 10000)
       return bucket + 3;
   if (duration < 100000)
       return bucket + 4;
   return bucket + 5;
}

/*
 * Return the average interrupt interval to take I/O performance
 * requirements into account. The smaller the average interrupt
 * interval to be, the more busy I/O activity, and thus the higher
 * the barrier to go to an expensive C state.
 */

/* 5 milisec sampling period */
#define SAMPLING_PERIOD     5000000

/* for I/O interrupt, we give 8x multiplier compared to C state latency*/
#define IO_MULTIPLIER       8

static inline s_time_t avg_intr_interval_us(void)
{
    struct menu_device *data = &__get_cpu_var(menu_devices);
    s_time_t    duration, now;
    s_time_t    avg_interval;
    unsigned int irq_sum;

    now = NOW();
    duration = (data->pf.duration + (now - data->pf.time_stamp)
            * (DECAY - 1)) / DECAY;

    irq_sum = (data->pf.irq_sum + (this_cpu(irq_count) - data->pf.irq_count_stamp)
            * (DECAY - 1)) / DECAY;

    if (irq_sum == 0)
        /* no irq recently, so return a big enough interval: 1 sec */
        avg_interval = 1000000;
    else
        avg_interval = duration / irq_sum / 1000; /* in us */

    if ( duration >= SAMPLING_PERIOD){
        data->pf.time_stamp = now;
        data->pf.duration = duration;
        data->pf.irq_count_stamp= this_cpu(irq_count);
        data->pf.irq_sum = irq_sum;
    }

    return avg_interval;
}

static unsigned int get_sleep_length_us(void)
{
    s_time_t us = (this_cpu(timer_deadline_start) - NOW()) / 1000;
    /*
     * while us < 0 or us > (u32)-1, return a large u32,
     * choose (unsigned int)-2000 to avoid wrapping while added with exit
     * latency because the latency should not larger than 2ms
     */
    return (us >> 32) ? (unsigned int)-2000 : (unsigned int)us;
}

static int menu_select(struct acpi_processor_power *power)
{
    struct menu_device *data = &__get_cpu_var(menu_devices);
    int i;
    s_time_t    io_interval;

    /*  TBD: Change to 0 if C0(polling mode) support is added later*/
    data->last_state_idx = CPUIDLE_DRIVER_STATE_START;
    data->exit_us = 0;

    /* determine the expected residency time, round up */
    data->expected_us = get_sleep_length_us();

    data->bucket = which_bucket(data->expected_us);

    io_interval = avg_intr_interval_us();

    /*
     * if the correction factor is 0 (eg first time init or cpu hotplug
     * etc), we actually want to start out with a unity factor.
     */
    if (data->correction_factor[data->bucket] == 0)
        data->correction_factor[data->bucket] = RESOLUTION * DECAY;

    /* Make sure to round up for half microseconds */
    data->predicted_us = DIV_ROUND(
            data->expected_us * data->correction_factor[data->bucket],
            RESOLUTION * DECAY);

    /* find the deepest idle state that satisfies our constraints */
    for ( i = CPUIDLE_DRIVER_STATE_START + 1; i < power->count; i++ )
    {
        struct acpi_processor_cx *s = &power->states[i];

        if (s->target_residency > data->predicted_us)
            break;
        if (s->latency * IO_MULTIPLIER > io_interval)
            break;
        /* TBD: we need to check the QoS requirment in future */
        data->exit_us = s->latency;
        data->last_state_idx = i;
    }

    return data->last_state_idx;
}

static void menu_reflect(struct acpi_processor_power *power)
{
    struct menu_device *data = &__get_cpu_var(menu_devices);
    unsigned int last_idle_us = power->last_residency;
    unsigned int measured_us;
    u64 new_factor;

    measured_us = last_idle_us;

    /*
     * We correct for the exit latency; we are assuming here that the
     * exit latency happens after the event that we're interested in.
     */
    if (measured_us > data->exit_us)
        measured_us -= data->exit_us;

    /* update our correction ratio */

    new_factor = data->correction_factor[data->bucket]
        * (DECAY - 1) / DECAY;

    if (data->expected_us > 0 && data->measured_us < MAX_INTERESTING)
        new_factor += RESOLUTION * measured_us / data->expected_us;
    else
        /*
         * we were idle so long that we count it as a perfect
         * prediction
         */
        new_factor += RESOLUTION;

    /*
     * We don't want 0 as factor; we always want at least
     * a tiny bit of estimated time.
     */
    if (new_factor == 0)
        new_factor = 1;

    data->correction_factor[data->bucket] = new_factor;
}

static int menu_enable_device(struct acpi_processor_power *power)
{
    struct menu_device *data = &per_cpu(menu_devices, power->cpu);

    memset(data, 0, sizeof(struct menu_device));

    return 0;
}

static struct cpuidle_governor menu_governor =
{
    .name =         "menu",
    .rating =       20,
    .enable =       menu_enable_device,
    .select =       menu_select,
    .reflect =      menu_reflect,
};

struct cpuidle_governor *cpuidle_current_governor = &menu_governor;
void menu_get_trace_data(u32 *expected, u32 *pred)
{
    struct menu_device *data = &__get_cpu_var(menu_devices);
    *expected = data->expected_us;
    *pred = data->predicted_us;
}