diff options
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/delay_timer/delay_timer.c | 23 | ||||
| -rw-r--r-- | drivers/delay_timer/generic_delay_timer.c | 82 |
2 files changed, 95 insertions, 10 deletions
diff --git a/drivers/delay_timer/delay_timer.c b/drivers/delay_timer/delay_timer.c index 0bee876f..ed7ed52e 100644 --- a/drivers/delay_timer/delay_timer.c +++ b/drivers/delay_timer/delay_timer.c @@ -48,19 +48,22 @@ void udelay(uint32_t usec) (ops->clk_div != 0) && (ops->get_timer_value != 0)); - uint32_t start, cnt, delta, delta_us; + uint32_t start, delta, total_delta; + + assert(usec < UINT32_MAX / ops->clk_div); - /* counter is decreasing */ start = ops->get_timer_value(); + + total_delta = (usec * ops->clk_div) / ops->clk_mult; + do { - cnt = ops->get_timer_value(); - if (cnt > start) { - delta = UINT32_MAX - cnt; - delta += start; - } else - delta = start - cnt; - delta_us = (delta * ops->clk_mult) / ops->clk_div; - } while (delta_us < usec); + /* + * If the timer value wraps around, the subtraction will + * overflow and it will still give the correct result. + */ + delta = start - ops->get_timer_value(); /* Decreasing counter */ + + } while (delta < total_delta); } /*********************************************************** diff --git a/drivers/delay_timer/generic_delay_timer.c b/drivers/delay_timer/generic_delay_timer.c new file mode 100644 index 00000000..4c364a30 --- /dev/null +++ b/drivers/delay_timer/generic_delay_timer.c @@ -0,0 +1,82 @@ +/* + * Copyright (c) 2016, ARM Limited and Contributors. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * Redistributions of source code must retain the above copyright notice, this + * list of conditions and the following disclaimer. + * + * Redistributions in binary form must reproduce the above copyright notice, + * this list of conditions and the following disclaimer in the documentation + * and/or other materials provided with the distribution. + * + * Neither the name of ARM nor the names of its contributors may be used + * to endorse or promote products derived from this software without specific + * prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + */ + +#include <arch_helpers.h> +#include <assert.h> +#include <bl_common.h> +#include <debug.h> +#include <delay_timer.h> +#include <platform.h> + +/* Ticks elapsed in one second by a signal of 1 MHz */ +#define MHZ_TICKS_PER_SEC 1000000 + +static timer_ops_t ops; + +static uint32_t get_timer_value(void) +{ + /* + * Generic delay timer implementation expects the timer to be a down + * counter. We apply bitwise NOT operator to the tick values returned + * by read_cntpct_el0() to simulate the down counter. The value is + * clipped from 64 to 32 bits. + */ + return (uint32_t)(~read_cntpct_el0()); +} + +void generic_delay_timer_init_args(uint32_t mult, uint32_t div) +{ + ops.get_timer_value = get_timer_value; + ops.clk_mult = mult; + ops.clk_div = div; + + timer_init(&ops); + + VERBOSE("Generic delay timer configured with mult=%u and div=%u\n", + mult, div); +} + +void generic_delay_timer_init(void) +{ + /* Value in ticks */ + unsigned int mult = MHZ_TICKS_PER_SEC; + + /* Value in ticks per second (Hz) */ + unsigned int div = plat_get_syscnt_freq2(); + + /* Reduce multiplier and divider by dividing them repeatedly by 10 */ + while ((mult % 10 == 0) && (div % 10 == 0)) { + mult /= 10; + div /= 10; + } + + generic_delay_timer_init_args(mult, div); +} + |