lkml.org 
[lkml]   [2014]   [Jun]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2] clk: exynos5420: Keep aclk66_peric enabled during boot
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.

Best regards,
Tomasz


\
 
 \ /
  Last update: 2014-06-05 21:21    [W:0.112 / U:0.192 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site