diff options
| author | Ruihong Luo <[email protected]> | 2023-07-13 08:42:36 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <[email protected]> | 2023-07-25 20:31:31 +0200 |
| commit | 748c5ea8b8796ae8ee80b8d3a3d940570b588d59 (patch) | |
| tree | dd8e0bc02ece832eaa42206d09ec0a8128516bfc | |
| parent | 57c984f6fe20ebb9306d6e8c09b4f67fe63298c6 (diff) | |
serial: 8250_dw: Preserve original value of DLF register
Preserve the original value of the Divisor Latch Fraction (DLF) register.
When the DLF register is modified without preservation, it can disrupt
the baudrate settings established by firmware or bootloader, leading to
data corruption and the generation of unreadable or distorted characters.
Fixes: 701c5e73b296 ("serial: 8250_dw: add fractional divisor support")
Cc: stable <[email protected]>
Signed-off-by: Ruihong Luo <[email protected]>
Link: https://lore.kernel.org/stable/20230713004235.35904-1-colorsu1922%40gmail.com
Reviewed-by: Ilpo Järvinen <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
| -rw-r--r-- | drivers/tty/serial/8250/8250_dwlib.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/drivers/tty/serial/8250/8250_dwlib.c b/drivers/tty/serial/8250/8250_dwlib.c index 75f32f054ebb..84843e204a5e 100644 --- a/drivers/tty/serial/8250/8250_dwlib.c +++ b/drivers/tty/serial/8250/8250_dwlib.c @@ -244,7 +244,7 @@ void dw8250_setup_port(struct uart_port *p) struct dw8250_port_data *pd = p->private_data; struct dw8250_data *data = to_dw8250_data(pd); struct uart_8250_port *up = up_to_u8250p(p); - u32 reg; + u32 reg, old_dlf; pd->hw_rs485_support = dw8250_detect_rs485_hw(p); if (pd->hw_rs485_support) { @@ -270,9 +270,11 @@ void dw8250_setup_port(struct uart_port *p) dev_dbg(p->dev, "Designware UART version %c.%c%c\n", (reg >> 24) & 0xff, (reg >> 16) & 0xff, (reg >> 8) & 0xff); + /* Preserve value written by firmware or bootloader */ + old_dlf = dw8250_readl_ext(p, DW_UART_DLF); dw8250_writel_ext(p, DW_UART_DLF, ~0U); reg = dw8250_readl_ext(p, DW_UART_DLF); - dw8250_writel_ext(p, DW_UART_DLF, 0); + dw8250_writel_ext(p, DW_UART_DLF, old_dlf); if (reg) { pd->dlf_size = fls(reg); |