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[PATCH] dz.c: Always check if it is safe to console_putchar()

To: Andrew Morton <akpm@linux-foundation.org>
Subject: [PATCH] dz.c: Always check if it is safe to console_putchar()
From: "Maciej W. Rozycki" <macro@linux-mips.org>
Date: Fri, 19 Oct 2007 21:18:03 +0100 (BST)
Cc: linux-mips@linux-mips.org, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org
Original-recipient: rfc822;linux-mips@linux-mips.org
Sender: linux-mips-bounce@linux-mips.org
 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 <macro@linux-mips.org>
---
 Tested with checkpatch.pl and at the run-time -- MIPS/Linux on a 
DECstation 5000/200.

 Please apply,

  Maciej

patch-mips-2.6.18-20060920-dz-putchar-0
diff -up --recursive --new-file 
linux-mips-2.6.18-20060920.macro/drivers/serial/dz.c 
linux-mips-2.6.18-20060920/drivers/serial/dz.c
--- linux-mips-2.6.18-20060920.macro/drivers/serial/dz.c        2006-11-23 
05:17:01.000000000 +0000
+++ linux-mips-2.6.18-20060920/drivers/serial/dz.c      2007-01-14 
00:07:02.000000000 +0000
@@ -686,7 +686,7 @@ static void dz_console_putchar(struct ua
        iob();
        spin_unlock_irqrestore(&dport->port.lock, flags);
 
-       while (loops--) {
+       do {
                trdy = dz_in(dport, DZ_CSR);
                if (!(trdy & DZ_TRDY))
                        continue;
@@ -697,7 +697,7 @@ static void dz_console_putchar(struct ua
                dz_out(dport, DZ_TCR, mask);
                iob();
                udelay(2);
-       }
+       } while (loops--);
 
        if (loops)                              /* Cannot send otherwise. */
                dz_out(dport, DZ_TDR, ch);

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