diff options
| author | Andy Shevchenko <andriy.shevchenko@linux.intel.com> | 2025-03-17 11:40:21 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-03-20 08:05:27 -0700 |
| commit | bd8cad85561b8de36f099404c332bf3e3dbe90f5 (patch) | |
| tree | ca1f354320d22b63c357b20ee74a5788b8ce782b | |
| parent | 067e95857021bb242099d6bd818e1c57a101802b (diff) | |
serial: 8250_dw: Comment possible corner cases in serial_out() implementation
8250 DesignWare driver uses a few custom implementations of the serial_out().
These implementations are carefully made to avoid infinite loops. But this is
not obvious from looking at the code. Comment the possible corner cases in
the respective functions.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20250317094021.1201512-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/serial/8250/8250_dw.c | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c index f068b8d7840a..1902f29444a1 100644 --- a/drivers/tty/serial/8250/8250_dw.c +++ b/drivers/tty/serial/8250/8250_dw.c @@ -107,11 +107,23 @@ static inline int dw8250_modify_msr(struct uart_port *p, int offset, int value) return value; } +/* + * This function is being called as part of the uart_port::serial_out() + * routine. Hence, it must not call serial_port_out() or serial_out() + * against the modified registers here, i.e. LCR. + */ static void dw8250_force_idle(struct uart_port *p) { struct uart_8250_port *up = up_to_u8250p(p); unsigned int lsr; + /* + * The following call currently performs serial_out() + * against the FCR register. Because it differs to LCR + * there will be no infinite loop, but if it ever gets + * modified, we might need a new custom version of it + * that avoids infinite recursion. + */ serial8250_clear_and_reinit_fifos(up); /* @@ -128,6 +140,11 @@ static void dw8250_force_idle(struct uart_port *p) serial_port_in(p, UART_RX); } +/* + * This function is being called as part of the uart_port::serial_out() + * routine. Hence, it must not call serial_port_out() or serial_out() + * against the modified registers here, i.e. LCR. + */ static void dw8250_check_lcr(struct uart_port *p, int offset, int value) { struct dw8250_data *d = to_dw8250_data(p->private_data); |