Re: [PATCH] ARM: delay: avoid clang -Wtautological-constant warning
From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Date: 2021-03-23 13:31:11
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On Tue, Mar 23, 2021 at 02:20:23PM +0100, Arnd Bergmann wrote:
From: Arnd Bergmann <arnd@arndb.de>
Passing an 8-bit constant into delay() triggers a warning when building
with 'make W=1' using clang:
drivers/clk/actions/owl-pll.c:182:2: error: result of comparison of constant 2000 with expression of type 'u8' (aka 'unsigned char') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
udelay(pll_hw->delay);
^~~~~~~~~~~~~~~~~~~~~
arch/arm/include/asm/delay.h:84:9: note: expanded from macro 'udelay'
((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() : \
~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~
arch/arm/mach-omap2/wd_timer.c:89:3: error: result of comparison of constant 2000 with expression of type 'u8' (aka 'unsigned char') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
udelay(oh->class->sysc->srst_udelay);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Shut up the warning by adding a cast to a 64-bit number. A cast to 'int'
would usually be sufficient, but would fail to cause a link-time error
for large 64-bit constants.What effect (if any) does this have on code generation when the argument is not constant? -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last! _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel