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lib: utils/serial: Ensure baudrate is non-zero before using

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RISC-V doesn't generate exceptions on divide-by-zero, but the result,
all bits set, is not likely what people expect either. In all cases
where we divide by baudrate there's a chance it's zero (when the DT
it came from is "bad"). To avoid difficult to debug situations, leave
baudrate dependent registers alone when baudrate is zero, as, also in
all cases, it appears we can skip initialization of those registers
and still [hopefully] have a functioning UART.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Andrew Jones 2022-07-18 19:20:28 +02:00 • committed by Anup Patel
parent 7198e1d06f
commit f27203525a
4 changed files with 13 additions and 6 deletions
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2
lib/utils/serial/gaisler-uart.c
View file

@ -70,7 +70,7 @@ int gaisler_uart_init(unsigned long base, u32 in_freq, u32 baudrate)
uart_base = (volatile char *)base;
/* Configure baudrate */
if (in_freq)
if (in_freq && baudrate)
set_reg(UART_REG_SCALER, in_freq / (baudrate * 8 + 7));
ctrl = get_reg(UART_REG_CTRL);

8
lib/utils/serial/shakti-uart.c
View file

@ -47,8 +47,12 @@ static struct sbi_console_device shakti_console = {
int shakti_uart_init(unsigned long base, u32 in_freq, u32 baudrate)
{
uart_base = (volatile char *)base;
u16 baud = (u16)(in_freq/(16 * baudrate));
writew(baud, uart_base + REG_BAUD);
u16 baud;
if (baudrate) {
baud = (u16)(in_freq / (16 * baudrate));
writew(baud, uart_base + REG_BAUD);
}
sbi_console_set_device(&shakti_console);

2
lib/utils/serial/sifive-uart.c
View file

@ -97,7 +97,7 @@ int sifive_uart_init(unsigned long base, u32 in_freq, u32 baudrate)
uart_baudrate = baudrate;
/* Configure baudrate */
if (in_freq)
if (in_freq && baudrate)
set_reg(UART_REG_DIV, uart_min_clk_divisor(in_freq, baudrate));
/* Disable interrupts */

7
lib/utils/serial/uart8250.c
View file

@ -93,7 +93,7 @@ static struct sbi_console_device uart8250_console = {
int uart8250_init(unsigned long base, u32 in_freq, u32 baudrate, u32 reg_shift,
u32 reg_width, u32 reg_offset)
{
u16 bdiv;
u16 bdiv = 0;
uart8250_base = (volatile char *)base + reg_offset;
uart8250_reg_shift = reg_shift;
@ -101,7 +101,10 @@ int uart8250_init(unsigned long base, u32 in_freq, u32 baudrate, u32 reg_shift,
uart8250_in_freq = in_freq;
uart8250_baudrate = baudrate;
bdiv = (uart8250_in_freq + 8 * uart8250_baudrate) / (16 * uart8250_baudrate);
if (uart8250_baudrate) {
bdiv = (uart8250_in_freq + 8 * uart8250_baudrate) /
(16 * uart8250_baudrate);
}
/* Disable all interrupts */
set_reg(UART_IER_OFFSET, 0x00);