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xlnx_psttc_timer.c
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xlnx_psttc_timer.c
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/*
* Copyright (c) 2020 Stephanos Ioannidis <root@stephanos.io>
* Copyright (c) 2018 Xilinx, Inc.
*
* SPDX-License-Identifier: Apache-2.0
*/
#define DT_DRV_COMPAT xlnx_ttcps
#include <zephyr/arch/cpu.h>
#include <zephyr/init.h>
#include <zephyr/irq.h>
#include <zephyr/sys_clock.h>
#include <soc.h>
#include <zephyr/drivers/timer/system_timer.h>
#include "xlnx_psttc_timer_priv.h"
#define TIMER_INDEX CONFIG_XLNX_PSTTC_TIMER_INDEX
#define TIMER_IRQ DT_INST_IRQN(0)
#define TIMER_BASE_ADDR DT_INST_REG_ADDR(0)
#define TIMER_CLOCK_FREQUECY DT_INST_PROP(0, clock_frequency)
#define TICKS_PER_SEC CONFIG_SYS_CLOCK_TICKS_PER_SEC
#define CYCLES_PER_SEC TIMER_CLOCK_FREQUECY
#define CYCLES_PER_TICK (CYCLES_PER_SEC / TICKS_PER_SEC)
#if defined(CONFIG_TEST)
const int32_t z_sys_timer_irq_for_test = DT_IRQN(DT_INST(0, xlnx_ttcps));
#endif
/*
* CYCLES_NEXT_MIN must be large enough to ensure that the timer does not miss
* interrupts. This value was conservatively set using the trial and error
* method, and there is room for improvement.
*/
#define CYCLES_NEXT_MIN (10000)
#define CYCLES_NEXT_MAX (XTTC_MAX_INTERVAL_COUNT)
BUILD_ASSERT(TIMER_CLOCK_FREQUECY ==
CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC,
"Configured system timer frequency does not match the TTC "
"clock frequency in the device tree");
BUILD_ASSERT(CYCLES_PER_SEC >= TICKS_PER_SEC,
"Timer clock frequency must be greater than the system tick "
"frequency");
BUILD_ASSERT((CYCLES_PER_SEC % TICKS_PER_SEC) == 0,
"Timer clock frequency is not divisible by the system tick "
"frequency");
#ifdef CONFIG_TICKLESS_KERNEL
static uint32_t last_cycles;
#endif
static uint32_t read_count(void)
{
/* Read current counter value */
return sys_read32(TIMER_BASE_ADDR + XTTCPS_COUNT_VALUE_OFFSET);
}
static void update_match(uint32_t cycles, uint32_t match)
{
uint32_t delta = match - cycles;
/* Ensure that the match value meets the minimum timing requirements */
if (delta < CYCLES_NEXT_MIN) {
match += CYCLES_NEXT_MIN - delta;
}
/* Write counter match value for interrupt generation */
sys_write32(match, TIMER_BASE_ADDR + XTTCPS_MATCH_0_OFFSET);
}
static void ttc_isr(const void *arg)
{
uint32_t cycles;
uint32_t ticks;
ARG_UNUSED(arg);
/* Acknowledge interrupt */
sys_read32(TIMER_BASE_ADDR + XTTCPS_ISR_OFFSET);
/* Read counter value */
cycles = read_count();
#ifdef CONFIG_TICKLESS_KERNEL
/* Calculate the number of ticks since last announcement */
ticks = (cycles - last_cycles) / CYCLES_PER_TICK;
/* Update last cycles count */
last_cycles = cycles;
#else
/* Update counter match value for the next interrupt */
update_match(cycles, cycles + CYCLES_PER_TICK);
/* Advance tick count by 1 */
ticks = 1;
#endif
/* Announce to the kernel*/
sys_clock_announce(ticks);
}
void sys_clock_set_timeout(int32_t ticks, bool idle)
{
#ifdef CONFIG_TICKLESS_KERNEL
uint32_t cycles;
uint32_t next_cycles;
/* Read counter value */
cycles = read_count();
/* Calculate timeout counter value */
if (ticks == K_TICKS_FOREVER) {
next_cycles = cycles + CYCLES_NEXT_MAX;
} else {
next_cycles = cycles + ((uint32_t)ticks * CYCLES_PER_TICK);
}
/* Set match value for the next interrupt */
update_match(cycles, next_cycles);
#endif
}
uint32_t sys_clock_elapsed(void)
{
#ifdef CONFIG_TICKLESS_KERNEL
uint32_t cycles;
/* Read counter value */
cycles = read_count();
/* Return the number of ticks since last announcement */
return (cycles - last_cycles) / CYCLES_PER_TICK;
#else
/* Always return 0 for tickful operation */
return 0;
#endif
}
uint32_t sys_clock_cycle_get_32(void)
{
/* Return the current counter value */
return read_count();
}
static int sys_clock_driver_init(void)
{
uint32_t reg_val;
/* Stop timer */
sys_write32(XTTCPS_CNT_CNTRL_DIS_MASK,
TIMER_BASE_ADDR + XTTCPS_CNT_CNTRL_OFFSET);
#ifdef CONFIG_TICKLESS_KERNEL
/* Initialise internal states */
last_cycles = 0;
#endif
/* Initialise timer registers */
sys_write32(XTTCPS_CNT_CNTRL_RESET_VALUE,
TIMER_BASE_ADDR + XTTCPS_CNT_CNTRL_OFFSET);
sys_write32(0, TIMER_BASE_ADDR + XTTCPS_CLK_CNTRL_OFFSET);
sys_write32(0, TIMER_BASE_ADDR + XTTCPS_INTERVAL_VAL_OFFSET);
sys_write32(0, TIMER_BASE_ADDR + XTTCPS_MATCH_0_OFFSET);
sys_write32(0, TIMER_BASE_ADDR + XTTCPS_MATCH_1_OFFSET);
sys_write32(0, TIMER_BASE_ADDR + XTTCPS_MATCH_2_OFFSET);
sys_write32(0, TIMER_BASE_ADDR + XTTCPS_IER_OFFSET);
sys_write32(XTTCPS_IXR_ALL_MASK, TIMER_BASE_ADDR + XTTCPS_ISR_OFFSET);
/* Reset counter value */
reg_val = sys_read32(TIMER_BASE_ADDR + XTTCPS_CNT_CNTRL_OFFSET);
reg_val |= XTTCPS_CNT_CNTRL_RST_MASK;
sys_write32(reg_val, TIMER_BASE_ADDR + XTTCPS_CNT_CNTRL_OFFSET);
/* Set match mode */
reg_val = sys_read32(TIMER_BASE_ADDR + XTTCPS_CNT_CNTRL_OFFSET);
reg_val |= XTTCPS_CNT_CNTRL_MATCH_MASK;
sys_write32(reg_val, TIMER_BASE_ADDR + XTTCPS_CNT_CNTRL_OFFSET);
/* Set initial timeout */
reg_val = IS_ENABLED(CONFIG_TICKLESS_KERNEL) ?
CYCLES_NEXT_MAX : CYCLES_PER_TICK;
sys_write32(reg_val, TIMER_BASE_ADDR + XTTCPS_MATCH_0_OFFSET);
/* Connect timer interrupt */
IRQ_CONNECT(TIMER_IRQ, 0, ttc_isr, 0, 0);
irq_enable(TIMER_IRQ);
/* Enable timer interrupt */
reg_val = sys_read32(TIMER_BASE_ADDR + XTTCPS_IER_OFFSET);
reg_val |= XTTCPS_IXR_MATCH_0_MASK;
sys_write32(reg_val, TIMER_BASE_ADDR + XTTCPS_IER_OFFSET);
/* Start timer */
reg_val = sys_read32(TIMER_BASE_ADDR + XTTCPS_CNT_CNTRL_OFFSET);
reg_val &= (~XTTCPS_CNT_CNTRL_DIS_MASK);
sys_write32(reg_val, TIMER_BASE_ADDR + XTTCPS_CNT_CNTRL_OFFSET);
return 0;
}
SYS_INIT(sys_clock_driver_init, PRE_KERNEL_2,
CONFIG_SYSTEM_CLOCK_INIT_PRIORITY);