2.6.38-stable review patch. If anyone has any objections, please let us know.
------------------ From: Yin Kangkai <[email protected]> commit 0d0389e5414c8950b1613e8bdc74289cde3d6d98 upstream. In 8250.c original ns16550 autoconfig code, we change the divisor latch when we goto to high speed mode, we're assuming the previous speed is legacy. This some times is not true. For example in a system with both CONFIG_SERIAL_8250 and CONFIG_SERIAL_8250_PNP set, in this case, the code (autoconfig) will be called twice, one in serial8250_init/probe() and the other is from serial_pnp_probe. When serial_pnp_probe calls the autoconfig for NS16550A, it's already in high speed mode, change the divisor latch (quot << 3) in this case will make the UART console garbled. CC: Greg Kroah-Hartman <[email protected]> CC: David Woodhouse <[email protected]> CC: [email protected] Signed-off-by: Yin Kangkai <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- drivers/tty/serial/8250.c | 32 ++++++++++++++++++++------------ 1 file changed, 20 insertions(+), 12 deletions(-) --- a/drivers/tty/serial/8250.c +++ b/drivers/tty/serial/8250.c @@ -954,6 +954,23 @@ static int broken_efr(struct uart_8250_p return 0; } +static inline int ns16550a_goto_highspeed(struct uart_8250_port *up) +{ + unsigned char status; + + status = serial_in(up, 0x04); /* EXCR2 */ +#define PRESL(x) ((x) & 0x30) + if (PRESL(status) == 0x10) { + /* already in high speed mode */ + return 0; + } else { + status &= ~0xB0; /* Disable LOCK, mask out PRESL[01] */ + status |= 0x10; /* 1.625 divisor for baud_base --> 921600 */ + serial_outp(up, 0x04, status); + } + return 1; +} + /* * We know that the chip has FIFOs. Does it have an EFR? The * EFR is located in the same register position as the IIR and @@ -1025,12 +1042,8 @@ static void autoconfig_16550a(struct uar quot = serial_dl_read(up); quot <<= 3; - status1 = serial_in(up, 0x04); /* EXCR2 */ - status1 &= ~0xB0; /* Disable LOCK, mask out PRESL[01] */ - status1 |= 0x10; /* 1.625 divisor for baud_base --> 921600 */ - serial_outp(up, 0x04, status1); - - serial_dl_write(up, quot); + if (ns16550a_goto_highspeed(up)) + serial_dl_write(up, quot); serial_outp(up, UART_LCR, 0); @@ -3025,15 +3038,10 @@ void serial8250_resume_port(int line) struct uart_8250_port *up = &serial8250_ports[line]; if (up->capabilities & UART_NATSEMI) { - unsigned char tmp; - /* Ensure it's still in high speed mode */ serial_outp(up, UART_LCR, 0xE0); - tmp = serial_in(up, 0x04); /* EXCR2 */ - tmp &= ~0xB0; /* Disable LOCK, mask out PRESL[01] */ - tmp |= 0x10; /* 1.625 divisor for baud_base --> 921600 */ - serial_outp(up, 0x04, tmp); + ns16550a_goto_highspeed(up); serial_outp(up, UART_LCR, 0); up->port.uartclk = 921600*16; _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
