linux-kernel - [PATCH] 8250: Don't delay after transmitter is ready.

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Message-Id: <1286304007-4715-1-git-send-email-ddaney@caviumnetworks.com>
Date:	Tue,  5 Oct 2010 11:40:07 -0700
From:	David Daney <ddaney@...iumnetworks.com>
To:	linux-serial@...r.kernel.org, gregkh@...e.de,
	linux-kernel@...r.kernel.org
Cc:	David Daney <ddaney@...iumnetworks.com>
Subject: [PATCH] 8250: Don't delay after transmitter is ready.

The loop in wait_for_xmitr() is delaying one extra uS after the ready
condition has been met.  Rewrite the loop to only delay if the
transmitter is not ready.

Signed-off-by: David Daney <ddaney@...iumnetworks.com>
---
 drivers/serial/8250.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 24110f6..31b8cca 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -1867,15 +1867,17 @@ static void wait_for_xmitr(struct uart_8250_port *up, int bits)
 	unsigned int status, tmout = 10000;
 
 	/* Wait up to 10ms for the character(s) to be sent. */
-	do {
+	for (;;) {
 		status = serial_in(up, UART_LSR);
 
 		up->lsr_saved_flags |= status & LSR_SAVE_FLAGS;
 
+		if ((status & bits) == bits)
+			break;
 		if (--tmout == 0)
 			break;
 		udelay(1);
-	} while ((status & bits) != bits);
+	}
 
 	/* Wait up to 1s for flow control if necessary */
 	if (up->port.flags & UPF_CONS_FLOW) {
-- 
1.7.2.2

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