Re: [PATCH] media: i2c: mt9m114: add CONFIG_COMMON_CLK dependency
From: Sakari Ailus
Date: Wed Dec 13 2023 - 03:33:00 EST
On Wed, Dec 13, 2023 at 08:09:03AM +0000, Sakari Ailus wrote:
> Hi Arnd,
>
> On Tue, Dec 12, 2023 at 10:18:04PM +0100, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@xxxxxxxx>
> >
> > With clang-16, building without COMMON_CLK triggers a range check on
> > udelay() because of a constant division-by-zero calculation:
> >
> > ld.lld: error: undefined symbol: __bad_udelay
> > >>> referenced by mt9m114.c
> > >>> drivers/media/i2c/mt9m114.o:(mt9m114_power_on) in archive vmlinux.a
> >
> > Avoid this by adding a Kconfig dependency that avoids the broken build.
>
> This sounds like an odd way to fix an issue with udelay(). On which arch
> does it happen? Wouldn't it be better to fix the udelay() problem in the
> source?
>
> A quick check reveals there are about 2400 files using udelay.
After discussing with Tomi, I think the driver could be improved, too, by
adding checks for clock frequency and avoiding an obvious potential
division by zero if clk_get_rate() happens to return 0. Switching to
fsleep() would probably address the Clang 16 issue, but that doesn't seem
to be the primary cause here anyway.
--
Sakari Ailus