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authorGravatar Thierry Reding <thierry.reding@gmail.com> 2014-12-18 10:09:42 +0100
committerGravatar Thierry Reding <thierry.reding@gmail.com> 2015-01-30 12:15:58 +0100
commitd2048c49152a414efcf8b2696896bc8803ef2f1e (patch)
tree32838cb723c326344bbdc03463ac89110af11769 /drivers/pwm/pwm-sun4i.c
parentLinux 3.19-rc1 (diff)
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pwm: atmel-hlcdc: Depend on HAVE_CLK
The include/linux/clk.h header defines dummy implementations for the various clk_*() functions if HAVE_CLK is not selected to improve build coverage in randconfig builds. The dummy implementation of clk_get_rate() returns 0, which causes the Atmel HLCDC PWM driver's atmel_hlcdc_pwm_config() implementation to end up calling: do_div(clk_period_ns, 0) On x86, do_div(n, base) will end up evaluating to this: n >>= ilog2(base) with base = 0, the implementation of ilog2() will call ____ilog2_NaN(), which is purposely undefined and results in a linker failure: ERROR: "____ilog2_NaN" [drivers/pwm/pwm-atmel-hlcdc.ko] undefined! The implementation of do_div() checks that base is a power of 2 before calling ilog2(). The compiler doesn't optimize this away, presumably because is_power_of_2() is an inline function and the compiler doesn't or can't inspect it closely enough. ilog2() being a macro it still ends up generating the ____ilog2_NaN() because of the constant 0. The root of the problem is that the driver really should be checking before possibly dividing by zero. That should eventually be fixed, but for now just assume that the clock runs at a sensible frequency when available. Reported-by: Jim Davis <jim.epost@gmail.com> Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com> Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Diffstat (limited to 'drivers/pwm/pwm-sun4i.c')
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