From dbab81281d3227af3d8a04aa748c5f41befa5d43 Mon Sep 17 00:00:00 2001 From: "Maciej W. Rozycki" Date: Thu, 7 Feb 2008 00:15:07 -0800 Subject: [PATCH] dz: always check if it is safe to console_putchar() Polled transmission is tricky enough with the DZ11 design. While "loop" is set to a high value, conceptually you are not allowed to transmit without checking whether the device offers the right transmission line (yes, it is the device that selects the line -- the driver has no control over it other than disabling the transmitter offered if it is the wrong one), so the loop has to be run at least once. Well, the '1977 or PDP11 view of how serial lines should be handled... Except that the serial interface used to be quite an impressive board back then rather than chip. Signed-off-by: Maciej W. Rozycki Cc: Jiri Slaby Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/serial/dz.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/serial/dz.c b/drivers/serial/dz.c index bbae5a220219..e1a2e413eb7d 100644 --- a/drivers/serial/dz.c +++ b/drivers/serial/dz.c @@ -685,7 +685,7 @@ static void dz_console_putchar(struct uart_port *uport, int ch) iob(); spin_unlock_irqrestore(&dport->port.lock, flags); - while (loops--) { + do { trdy = dz_in(dport, DZ_CSR); if (!(trdy & DZ_TRDY)) continue; @@ -696,7 +696,7 @@ static void dz_console_putchar(struct uart_port *uport, int ch) dz_out(dport, DZ_TCR, mask); iob(); udelay(2); - } + } while (loops--); if (loops) /* Cannot send otherwise. */ dz_out(dport, DZ_TDR, ch); -- GitLab