From: Patrice Chotard <patrice.chot...@st.com>
Simplify baud rate register formula and use the oversampling
uart feature.
This code is aligned with what is implemented in kernel driver
drivers/tty/serial/stm32-usart.c since kernel v4.9.
Signed-off-by: Patrice Chotard <patrice.chot...@st.com>
Reviewed-by: Christophe KERELLO <christophe.kere...@st.com>
Reviewed-by: Patrick DELAUNAY <patrick.delau...@st.com>
Acked-by: Vikas MANOCHA <vikas.mano...@st.com>
---
drivers/serial/serial_stm32x7.c | 21 +++++++++++++++------
drivers/serial/serial_stm32x7.h | 3 ++-
2 files changed, 17 insertions(+), 7 deletions(-)
diff --git a/drivers/serial/serial_stm32x7.c b/drivers/serial/serial_stm32x7.c
index 27e0068..98cbac8 100644
--- a/drivers/serial/serial_stm32x7.c
+++ b/drivers/serial/serial_stm32x7.c
@@ -20,7 +20,7 @@ static int stm32_serial_setbrg(struct udevice *dev, int
baudrate)
{
struct stm32x7_serial_platdata *plat = dev->platdata;
struct stm32_usart *const usart = plat->base;
- u32 clock, int_div, frac_div, tmp;
+ u32 clock, int_div, mantissa, fraction, oversampling;
if (((u32)usart & STM32_BUS_MASK) == APB1_PERIPH_BASE)
clock = clock_get(CLOCK_APB1);
@@ -29,11 +29,20 @@ static int stm32_serial_setbrg(struct udevice *dev, int
baudrate)
else
return -EINVAL;
- int_div = (25 * clock) / (4 * baudrate);
- tmp = ((int_div / 100) << USART_BRR_M_SHIFT) & USART_BRR_M_MASK;
- frac_div = int_div - (100 * (tmp >> USART_BRR_M_SHIFT));
- tmp |= (((frac_div * 16) + 50) / 100) & USART_BRR_F_MASK;
- writel(tmp, &usart->brr);
+ int_div = DIV_ROUND_CLOSEST(clock, baudrate);
+
+ if (int_div < 16) {
+ oversampling = 8;
+ setbits_le32(&usart->cr1, USART_CR1_OVER8);
+ } else {
+ oversampling = 16;
+ clrbits_le32(&usart->cr1, USART_CR1_OVER8);
+ }
+
+ mantissa = (int_div / oversampling) << USART_BRR_M_SHIFT;
+ fraction = int_div % oversampling;
+
+ writel(mantissa | fraction, &usart->brr);
return 0;
}
diff --git a/drivers/serial/serial_stm32x7.h b/drivers/serial/serial_stm32x7.h
index 6190d67..d11865c 100644
--- a/drivers/serial/serial_stm32x7.h
+++ b/drivers/serial/serial_stm32x7.h
@@ -23,8 +23,9 @@ struct stm32_usart {
};
-#define USART_CR1_RE (1 << 2)
+#define USART_CR1_OVER8 (1 << 15)
#define USART_CR1_TE (1 << 3)
+#define USART_CR1_RE (1 << 2)
#define USART_CR1_UE (1 << 0)
#define USART_SR_FLAG_RXNE (1 << 5)
--
1.9.1
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