drivers/uart/sifive.c: Fix divisor calculation
The divisor is calculated using the following formula:
div = (frequency / baudrate) - 1;
The current implementation however essentially calculates:
div = (frequency / baudrate);
Signed-off-by: Maximilian Brune <maximilian.brune@9elements.com>
Change-Id: I8a0898ce9016a70c0f91dc8a99fc1cf9e46d20c4
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79951
Reviewed-by: ron minnich <rminnich@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
diff --git a/src/drivers/uart/sifive.c b/src/drivers/uart/sifive.c
index d1b89dc..815a0cf 100644
--- a/src/drivers/uart/sifive.c
+++ b/src/drivers/uart/sifive.c
@@ -47,9 +47,16 @@
void uart_init(unsigned int idx)
{
- unsigned int div;
- div = uart_baudrate_divisor(get_uart_baudrate(),
- uart_platform_refclk(), uart_input_clock_divider());
+ /*
+ * according to FU540/FU740 manual:
+ * f_baud = f_in / (div + 1)
+ * <=>
+ * div = (f_in / f_baud) - 1
+ */
+ unsigned int div = uart_baudrate_divisor(get_uart_baudrate(), uart_platform_refclk(),
+ uart_input_clock_divider());
+ div -= 1;
+
sifive_uart_init(uart_platform_baseptr(idx), div);
}