From f27203525aa2fc20d0074feb892a6f8433f84e3a Mon Sep 17 00:00:00 2001 From: Andrew Jones Date: Mon, 18 Jul 2022 19:20:28 +0200 Subject: [PATCH] lib: utils/serial: Ensure baudrate is non-zero before using 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 Reviewed-by: Anup Patel --- lib/utils/serial/gaisler-uart.c | 2 +- lib/utils/serial/shakti-uart.c | 8 ++++++-- lib/utils/serial/sifive-uart.c | 2 +- lib/utils/serial/uart8250.c | 7 +++++-- 4 files changed, 13 insertions(+), 6 deletions(-) diff --git a/lib/utils/serial/gaisler-uart.c b/lib/utils/serial/gaisler-uart.c index 5f30ee43..eec75cca 100644 --- a/lib/utils/serial/gaisler-uart.c +++ b/lib/utils/serial/gaisler-uart.c @@ -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); diff --git a/lib/utils/serial/shakti-uart.c b/lib/utils/serial/shakti-uart.c index 35569356..8769cb26 100644 --- a/lib/utils/serial/shakti-uart.c +++ b/lib/utils/serial/shakti-uart.c @@ -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); diff --git a/lib/utils/serial/sifive-uart.c b/lib/utils/serial/sifive-uart.c index 7078611a..3581d47a 100644 --- a/lib/utils/serial/sifive-uart.c +++ b/lib/utils/serial/sifive-uart.c @@ -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 */ diff --git a/lib/utils/serial/uart8250.c b/lib/utils/serial/uart8250.c index 38ea11af..99bf1bf7 100644 --- a/lib/utils/serial/uart8250.c +++ b/lib/utils/serial/uart8250.c @@ -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);