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TF-A: Fix non-standard frequency issue in udelay 

Previous implementation of timers assumed that clk_div has pretty
representation in MHz (10MHz, 100MHz, etc). Unusual frequencies
(99.99MHz) were causing assertion error and made udelay unusable.

Signed-off-by: Max Shvetsov <maksims.svecovs@arm.com>
Change-Id: Ic915fff224369d113fd9f8edbcfff169fca8beac
This commit is contained in:
Max Shvetsov 2019-10-31 08:35:02 +00:00
parent 5d71d3f624
commit f2976bdda8
1 changed files with 15 additions and 5 deletions
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20
drivers/delay_timer/delay_timer.c
View File

@ -1,5 +1,5 @@
/* /*
* Copyright (c) 2015-2018, ARM Limited and Contributors. All rights reserved. * Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
* *
* SPDX-License-Identifier: BSD-3-Clause * SPDX-License-Identifier: BSD-3-Clause
*/ */
@ -27,23 +27,32 @@ void udelay(uint32_t usec)
(timer_ops->clk_div != 0U) && (timer_ops->clk_div != 0U) &&
(timer_ops->get_timer_value != NULL)); (timer_ops->get_timer_value != NULL));
uint32_t start, delta, total_delta; uint32_t start, delta;
uint64_t total_delta;
assert(usec < (UINT32_MAX / timer_ops->clk_div)); assert(usec < (UINT64_MAX / timer_ops->clk_div));
start = timer_ops->get_timer_value(); start = timer_ops->get_timer_value();
/* Add an extra tick to avoid delaying less than requested. */ /* Add an extra tick to avoid delaying less than requested. */
total_delta = total_delta =
div_round_up(usec * timer_ops->clk_div, div_round_up((uint64_t)usec * timer_ops->clk_div,
timer_ops->clk_mult) + 1U; timer_ops->clk_mult) + 1U;
/*
* Precaution for the total_delta ~ UINT32_MAX and the fact that we
* cannot catch every tick of the timer.
* For example 100MHz timer over 25MHz APB will miss at least 4 ticks.
* 1000U is an arbitrary big number which is believed to be sufficient.
*/
assert(total_delta < (UINT32_MAX - 1000U));
do { do {
/* /*
* If the timer value wraps around, the subtraction will * If the timer value wraps around, the subtraction will
* overflow and it will still give the correct result. * overflow and it will still give the correct result.
* delta is decreasing counter
*/ */
delta = start - timer_ops->get_timer_value(); /* Decreasing counter */ delta = start - timer_ops->get_timer_value();
} while (delta < total_delta); } while (delta < total_delta);
} }
@ -54,6 +63,7 @@ void udelay(uint32_t usec)
***********************************************************/ ***********************************************************/
void mdelay(uint32_t msec) void mdelay(uint32_t msec)
{ {
assert((msec * 1000UL) < UINT32_MAX);
udelay(msec * 1000U); udelay(msec * 1000U);
} }