From b15bfbe6427712d1b992bf806a6df9c05002a0a4 Mon Sep 17 00:00:00 2001 From: James Hogan Date: Sat, 4 Mar 2017 13:09:58 +0000 Subject: serial: 8250_dw: Fix breakage when HAVE_CLK=n Commit 6a171b299379 ("serial: 8250_dw: Allow hardware flow control to be used") recently broke the 8250_dw driver on platforms which don't select HAVE_CLK, as dw8250_set_termios() gets confused by the behaviour of the fallback HAVE_CLK=n clock API in linux/clk.h which pretends everything is fine but returns (valid) NULL clocks and 0 HZ clock rates. That 0 rate is written into the uartclk resulting in a crash at boot, e.g. on Cavium Octeon III based UTM-8 we get something like this: 1180000000800.serial: ttyS0 at MMIO 0x1180000000800 (irq = 41, base_baud = 25000000) is a OCTEON ------------[ cut here ]------------ WARNING: CPU: 2 PID: 1 at drivers/tty/serial/serial_core.c:441 uart_get_baud_rate+0xfc/0x1f0 ... Call Trace: ... [] uart_get_baud_rate+0xfc/0x1f0 [] serial8250_do_set_termios+0xb0/0x440 [] uart_set_options+0xe8/0x190 [] serial8250_console_setup+0x84/0x158 [] univ8250_console_setup+0x54/0x70 [] register_console+0x1c8/0x418 [] uart_add_one_port+0x434/0x4b0 [] serial8250_register_8250_port+0x2d8/0x440 [] dw8250_probe+0x388/0x5e8 ... The clock API is defined such that NULL is a valid clock handle so it wouldn't be right to check explicitly for NULL. Instead treat a clk_round_rate() return value of 0 as an error which prevents uartclk being overwritten. Fixes: 6a171b299379 ("serial: 8250_dw: Allow hardware flow control to be used") Signed-off-by: James Hogan Cc: Kefeng Wang Cc: David Daney Cc: Russell King Cc: linux-serial@vger.kernel.org Cc: linux-clk@vger.kernel.org Cc: linux-mips@linux-mips.org Cc: bcm-kernel-feedback-list@broadcom.com Reviewed-by: Andy Shevchenko Reviewed-by: Jason Uy Reviewed-by: Heiko Stuebner Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250/8250_dw.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/tty') diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c index 223ac234ddb2..e65808c482f1 100644 --- a/drivers/tty/serial/8250/8250_dw.c +++ b/drivers/tty/serial/8250/8250_dw.c @@ -267,6 +267,8 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios, rate = clk_round_rate(d->clk, baud * 16); if (rate < 0) ret = rate; + else if (rate == 0) + ret = -ENOENT; else ret = clk_set_rate(d->clk, rate); clk_prepare_enable(d->clk); -- cgit v1.2.3-59-g8ed1b