Subject: [PATCH] clk: samsung: Fix Exynos 5420 pinctrl setup and clock disable failure due to domain being gated

From: [email-masked] (Kevin Hilman)
Date: Wed, 10 Dec 2014 09:35:31 -0800

Sylwester Nawrocki <[email-masked]> writes:

> On 09/12/14 13:59, Krzysztof Kozlowski wrote:
>> On pi?, 2014-12-05 at 15:15 +0100, Krzysztof Kozlowski wrote:
>>> > Audio subsystem clocks are located in separate block. On Exynos 5420 if
>>> > clock for this block (from main clock domain) 'mau_epll' is gated then
>>> > any read or write to audss registers will block.
>>> > 
>>> > This kind of boot hang was observed on Arndale Octa and Peach Pi/Pit
>>> > after introducing runtime PM to pl330 DMA driver. After that commit the
>>> > 'mau_epll' was gated, because the "amba" clock was disabled and there
>>> > were no more users of mau_epll.
>>> > 
>>> > The system hang on one of steps:
>>> > 1. Disabling unused clocks from audss block.
>>> > 2. During audss GPIO setup (just before probing i2s0 because
>>> >    samsung_pinmux_setup() tried to access memory from audss block which was
>>> >    gated.
>>> > 
>>> > Add a workaround for this by enabling the 'mau_epll' clock in probe.
>>> > 
>>> > Signed-off-by: Krzysztof Kozlowski <[email-masked]>
>>> > ---
>>> >  drivers/clk/samsung/clk-exynos-audss.c | 29 ++++++++++++++++++++++++++++-
>>> >  1 file changed, 28 insertions(+), 1 deletion(-)
>>
>> Sorry for pinging so quick but merge window is open and it looks like
>> booting Exynos542x boards will be broken (because pl330 will no longer
>> hold adma clock enabled so whole audss domain will be gated).
>> 
>> This is a non-intrusive workaround for that issue, as wanted by
>> Sylwester:
>> https://lkml.org/lkml/2014/12/5/223
>> 
>> Any comments on this?
>
> The patch looks OK to me, it would be good though if someone else
> has confirmed it fixes the bug. I don't have any clock patches queued
> at the moment. Perhaps you could apply it directly, Mike ?

I confirm it fixes the boot hang in linux-next (next-20141210) on my
exynos5800-peach-pi and exynos5420-arndale-octa.  Tested both
exynos_defconfig and multi_v7_defconfig.

Tested-by: Kevin Hilman <[email-masked]>

Kevin