bug in PL011 console

[Jassi Brar]

2010/12/24 Uwe Kleine-König <u.kleine-koenig at pengutronix.de>:
> On Thu, Dec 23, 2010 at 03:08:41PM +0000, Russell King - ARM Linux wrote:
>> On Thu, Dec 23, 2010 at 04:02:34PM +0100, Uwe Kleine-König wrote:
>> > Steven told me on irc that sleeping was not allowed in the console write
>> > callback.  Maybe this didn't show up earlier because not all clk
>> > implementations sleep as mxs' does.
>> >
>> > I think the only possible fix is to do the clk_enable in the setup
>> > callback instead of per-write.
>> >
>> > Will send a patch as follow up.
>>
>> We really need to sort out what's expected from the CLK API.  The drivers
>> I write assume that it's absolutely fine to call clk_enable/clk_disable
>> from IRQ context, and for the platforms I implemented the CLK API for,
>> that's absolutely true.
> The common struct clk patch[1] by Jeremy Kerr sleeps, too.  And I think
> most people who commented to this series thought that this is the right
> behaviour.

Personally, I am not as against atomic clocks as having two versions
of the clock - atomic
and sleepable, in the API.
I favor sleepable version because with the clock hierarchies becoming so complex
in latest SoCs, it would be difficult to write a 'smart' clock
management sub-system
that could setup and enable all 'parent' clocks upon enabling a clock.
Especially, managing mux'es at levels much lower than pll. FWIK,
drivers have tough
time managing such parent clocks.