linux-kernel - Strange arch/mips/delay.c

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Date:	Sat, 1 Aug 2009 19:37:18 +0200
From:	Loïc Grenié <loic.grenie@...il.com>
To:	linux-kernel <linux-kernel@...r.kernel.org>,
	Ralf Baechle <ralf@...ux-mips.org>
Subject: Strange arch/mips/delay.c

  I could not compile for mips without something similar to the
following patch. As far as I can say __udelay and __ndelay
are costly nops (with __ndelay not compiling at all) without
the patch.

  At that point, it might be interesting to change
the 0x00000005uLL by 0x00000045uLL and the >> 32
by >> 36 (the precision is much better and the cost
should be the same -- obviously there is a slightly higher
risk of overlow).

    Thanks,

           Loïc Grenié

Signed-off-by: Loic Grenie <loic.grenie@...il.com>

--- a/arch/mips/lib/delay.c
+++ b/arch/mips/lib/delay.c
@@ -43,7 +43,7 @@ void __udelay(unsigned long us)
 {
        unsigned int lpj = current_cpu_data.udelay_val;

-       __delay((us * 0x000010c7 * HZ * lpj) >> 32);
+       __delay((us * 0x000010c7uLL * HZ * lpj) >> 32);
 }
 EXPORT_SYMBOL(__udelay);

@@ -51,6 +51,6 @@ void __ndelay(unsigned long ns)
 {
        unsigned int lpj = current_cpu_data.udelay_val;

-       __delay((us * 0x00000005 * HZ * lpj) >> 32);
+       __delay((ns * 0x00000005uLL * HZ * lpj) >> 32);
 }
 EXPORT_SYMBOL(__ndelay);
--
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