Re: [PATCH v2] clk: exynos4: Add CLK_GET_RATE_NOCACHE flag for the Exynos4x12 ISP clocks

[Mike Turquette <mturquette@linaro.org>]

Quoting Sylwester Nawrocki (2013-07-26 15:04:30)
> On 07/26/2013 10:30 PM, Mike Turquette wrote:
> > Quoting Sylwester Nawrocki (2013-07-25 14:07:05)
> >> From: Sylwester Nawrocki<s.nawrocki@samsung.com>
> >>
> >> The ISP clock registers belong to the ISP power domain and may change
> >> their values if this power domain is switched off/on. Add
> >> CLK_GET_RATE_NOCACHE flags to ensure we do not rely on invalid cached
> >> data when setting or getting frequency of those clocks.
> >>
> >> Signed-off-by: Sylwester Nawrocki<s.nawrocki@samsung.com>
> >> Signed-off-by: Kyungmin Park<kyungmin.park@samsung.com>
> >
> > Thanks for the fix. I've taken into clk-fixes. Is there a specific
> > regression this fixes (besides just having wrong clock rates). I can
> > amend the changelog if you have an example (e.g. device X explodes).
> 
> Hmm, yes, this fixes a pretty serious problem. There is a companion
> commit [1] already in Linus' tree, more details can be found there.
> 
> Perhaps something like this could be added:
> 
> "Otherwise the FIMC-IS Cortex-A5 core and AXI bus clocks have
> incorrect frequencies, which breaks the ISP operation and starting
> the video pipeline fails with timeouts reported by the FIMC-IS
> firmware.
> 
> See related commit 722a860ecb29aa34ec6f7d7f32b949209e8
> "[media] exynos4-is: Fix FIMC-IS clocks initialization" for more
> details."

That's great.

Thanks,
Mike

> 
> [1] 
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit?id=722a860ecb29aa34ec6f7d7f32b949209e86a2f3
> 
> Thanks,
> Sylwester