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i2c_software: Fix i2c_delay()

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The i2c_delay() function did not properly handle counter rollovers.
It also performed an expensive run-time divide.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor 2025-04-06 14:17:55 -04:00
parent 050bc33241
commit 655861cf12
1 changed files with 9 additions and 12 deletions
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21
src/i2c_software.c
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@ -1,11 +1,12 @@
// Software I2C emulation
//
// Copyright (C) 2023 Kevin O'Connor <kevin@koconnor.net>
// Copyright (C) 2023-2025 Kevin O'Connor <kevin@koconnor.net>
// Copyright (C) 2023 Alan.Ma <tech@biqu3d.com>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include <string.h> // memcpy
#include "autoconf.h" // CONFIG_CLOCK_FREQ
#include "board/gpio.h" // gpio_out_setup
#include "board/internal.h" // gpio_peripheral
#include "board/misc.h" // timer_read_time
@ -17,7 +18,7 @@ struct i2c_software {
struct gpio_out scl_out, sda_out;
struct gpio_in scl_in, sda_in;
uint8_t addr;
unsigned int ticks;
uint32_t ticks;
};
void
@ -25,7 +26,7 @@ command_i2c_set_software_bus(uint32_t *args)
{
struct i2cdev_s *i2c = i2cdev_oid_lookup(args[0]);
struct i2c_software *is = alloc_chunk(sizeof(*is));
is->ticks = 1000000 / 100 / 2; // 100KHz
is->ticks = CONFIG_CLOCK_FREQ / (100000 * 2); // 100KHz
is->addr = (args[4] & 0x7f) << 1; // address format shifted
is->scl_in = gpio_in_setup(args[1], 1);
is->scl_out = gpio_out_setup(args[1], 1);
@ -44,16 +45,12 @@ DECL_COMMAND(command_i2c_set_software_bus,
#else
static unsigned int
nsecs_to_ticks(uint32_t ns)
{
return timer_from_us(ns * 1000) / 1000000;
}
static void
i2c_delay(unsigned int ticks) {
unsigned int t = timer_read_time() + nsecs_to_ticks(ticks);
while (t > timer_read_time());
i2c_delay(uint32_t ticks)
{
uint32_t end = timer_read_time() + ticks;
while (timer_is_before(timer_read_time(), end))
;
}
#endif