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SubjectRe: [PATCH v2] clk: exynos5420: Keep aclk66_peric enabled during boot
From
Tomasz,

On Thu, Jun 5, 2014 at 12:14 PM, Tomasz Figa <tomasz.figa@gmail.com> wrote:
> On 05.06.2014 20:48, Doug Anderson wrote:
>> Tomasz / Mike,
>>
>> On Fri, May 30, 2014 at 9:32 AM, Doug Anderson <dianders@chromium.org> wrote:
>>> Right now if you've got earlyprintk enabled on exynos5420-peach-pit
>>> then you'll get a hang on boot. Here's why:
>>>
>>> 1. The i2c-s3c2410 driver will probe at subsys_initcall. It will
>>> enable its clock and disable it. This is the clock "i2c2".
>>> 2. The act of disabling "i2c2" will disable its parents. In this case
>>> the parent is "aclk66_peric". There are no other children of
>>> "aclk66_peric" officially enabled, so "aclk66_peric" will be turned
>>> off (despite being CLK_IGNORE_UNUSED, but that's by design).
>>> 3. The next time you try to earlyprintk you'll do so without the UART
>>> clock enabled. That's because the UART clocks are also children of
>>> "aclk66_peric". You'll hang.
>>>
>>> There's no good place to put a clock enable for earlyprintk, which is
>>> handled by a bunch of assembly code. The best we can do is to handle
>>> this in the clock driver.
>>>
>>> Signed-off-by: Doug Anderson <dianders@chromium.org>
>>> Tested-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
>>> ---
>>> Changes in v2:
>>> - Use GATE_A and clk_get(). Save the clock for putting later.
>>> - Return 0 from exynos5420_clk_late_init().
>>>
>>> drivers/clk/samsung/clk-exynos5420.c | 33 +++++++++++++++++++++++++++++++--
>>> 1 file changed, 31 insertions(+), 2 deletions(-)
>>
>> Are there other changes you'd like me to make to this? It would be
>> really nice to get this in for 3.16 so the system doesn't just
>> mysteriously hang when you use earlyprintk.
>
> We can probably take this as an -rc fix, so it should be fine.
>
> However I still don't see the point of exporting this clock and
> polluting the global clkdev namespace. Even the diffstat looks better in v1.

OK, I'm happy to go back to v1 with the addition of the "return 0".

Mike: are you OK with that?


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