UbiquitousOS
/
OpenCloudOS-Kernel
mirror of https://gitee.com/OpenCloudOS/OpenCloudOS-Kernel.git
11
0
Fork 0
Code Issues Projects Releases Wiki Activity

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: 701c5e73b2 ("serial: 8250_dw: add fractional divisor support")
Cc: stable <stable@kernel.org>
Signed-off-by: Ruihong Luo <colorsu1922@gmail.com>
Link: https://lore.kernel.org/stable/20230713004235.35904-1-colorsu1922%40gmail.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230713004235.35904-1-colorsu1922@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ruihong Luo 2023-07-13 08:42:36 +08:00 committed by Greg Kroah-Hartman
parent 57c984f6fe
commit 748c5ea8b8
1 changed files with 4 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/tty/serial/8250/8250_dwlib.c
View File

@ -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);