Re: [PATCH] media: i2c: mt9m114: add CONFIG_COMMON_CLK dependency

[Sakari Ailus]

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