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drivers/watchdog: wwdg stm32: fix to support all available prescalers

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As older series supported only 4 different prescaler values the
highest prescaler value was hardcoded. Newer series support 8
programmable prescaler values, therefore take the allowed values from
ll_wwdg header file.

Signed-off-by: Thomas Stranger <thomas.stranger@outlook.com>
This commit is contained in:
Thomas Stranger 2021-03-05 18:14:27 +01:00 • committed by Carles Cufí
commit 980fb6c0df
1 changed files with 16 additions and 3 deletions
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19
drivers/watchdog/wdt_wwdg_stm32.c
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@ -33,6 +33,16 @@ LOG_MODULE_REGISTER(wdt_wwdg_stm32);
#error "WWDG CFR WDGTB position not defined for soc"
#endif
/*
* additinally to the internal divider, the clock is divided by a
* programmable prescaler.
*/
#if defined(LL_WWDG_PRESCALER_128)
#define WWDG_PRESCALER_EXPONENT_MAX 7 /* 2^7 = 128 */
#elif defined(LL_WWDG_PRESCALER_8)
#define WWDG_PRESCALER_EXPONENT_MAX 3 /* 2^3 = 8 */
#endif
/* The timeout of the WWDG in milliseconds is calculated by the below formula:
*
* t_WWDG = 1000 * ((counter & 0x3F) + 1) / f_WWDG (ms)
@ -49,7 +59,8 @@ LOG_MODULE_REGISTER(wdt_wwdg_stm32);
* where:
* - f_PCLK: the clock frequency of the system
* - 4096: the constant internal divider
* - prescaler: the programmable divider with valid values of 1, 2, 4 or 8
* - prescaler: the programmable divider with valid values of 1, 2, 4 or 8,
* and for some series additionally 16, 32, 64 and 128
*
* The minimum timeout is calculated with:
* - counter = 0x40
@ -128,8 +139,10 @@ static void wwdg_stm32_convert_timeout(const struct device *dev,
*prescaler_exp = 0U;
*counter = 0;
for (*prescaler_exp = 0; *prescaler_exp <= 3; (*prescaler_exp)++) {
wwdg_freq = ((float)clock_freq) / WWDG_INTERNAL_DIVIDER / (1 << *prescaler_exp);
for (*prescaler_exp = 0; *prescaler_exp <= WWDG_PRESCALER_EXPONENT_MAX;
(*prescaler_exp)++) {
wwdg_freq = ((float)clock_freq) / WWDG_INTERNAL_DIVIDER
/ (1 << *prescaler_exp);
/* +1 to ceil the result, which may lose from truncation */
*counter = (uint32_t)(timeout_s * wwdg_freq + 1) - 1;
*counter += WWDG_RESET_LIMIT;