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stm32f0: Change uart clock to HSI

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When waking up from sleep, the real CPU_CLOCK is a lie for a moment(since we
cannot switch to the real clock during the first character) so the first
character will be corrupted.

The UART clock is now sourced from HSI(8MHz) which is available from the first
moment after the cpu wakes up from sleep.

BUG=None
TEST=Console should work.
When waking up(not implemented yet) it will also not lose a character
BRANCH=None

Change-Id: Ia12ed0634290f3edadfe3471b311759c3176260e
Signed-off-by: Alexandru M Stan <amstan@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/218728
Reviewed-by: Alec Berg <alecaberg@chromium.org>
Tested-by: Alec Berg <alecaberg@chromium.org>
Commit-Queue: Alec Berg <alecaberg@chromium.org>
This commit is contained in:
Alexandru M Stan
2014-09-17 15:58:39 -07:00
committed by chrome-internal-fetch
parent 2be0577fe0
commit 6395dbea0c
1 changed files with 22 additions and 1 deletions
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23
chip/stm32/uart.c
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@@ -194,7 +194,20 @@ DECLARE_IRQ(STM32_IRQ_USART(UARTN), uart_interrupt, 2);
*/
static void uart_freq_change(void)
{
int div = DIV_ROUND_NEAREST(clock_get_freq(), CONFIG_UART_BAUD_RATE);
int freq;
int div;
#if defined(CHIP_FAMILY_STM32F0) && (UARTN <= 2)
/*
* UART is clocked from HSI (8MHz) to allow it to work when waking
* up from sleep
*/
freq = 8000000;
#else
/* UART clocked from the main clock */
freq = clock_get_freq();
#endif
div = DIV_ROUND_NEAREST(freq, CONFIG_UART_BAUD_RATE);
#if defined(CHIP_FAMILY_STM32L) || defined(CHIP_FAMILY_STM32F0)
if (div / 16 > 0) {
@@ -223,6 +236,14 @@ DECLARE_HOOK(HOOK_FREQ_CHANGE, uart_freq_change, HOOK_PRIO_DEFAULT);
void uart_init(void)
{
/* Enable USART clock */
#ifdef CHIP_FAMILY_STM32F0
#if (UARTN == 1)
STM32_RCC_CFGR3 |= 0x0003; /* USART1 clock source from HSI(8MHz) */
#elif (UARTN == 2)
STM32_RCC_CFGR3 |= 0x0300; /* USART2 clock source from HSI(8MHz) */
#endif /* UARTN */
#endif /* CHIP_FAMILY_STM32F0 */
#if (UARTN == 1)
STM32_RCC_APB2ENR |= STM32_RCC_PB2_USART1;
#else