Clock register in early init
mturquette at ti.com
Mon May 21 14:05:57 EDT 2012
On Mon, May 21, 2012 at 1:46 AM, Peter De Schrijver
<pdeschrijver at nvidia.com> wrote:
>> On OMAP I think the only "gotcha" is setting up the timer. One
>> solution is to open code the register reads and the rate calculation
>> in the timer code. That is ugly... but it works.
>> > Which advantages do you see in dynamically allocating all this?
>> There are many but I'll name a couple. The most significant point is
>> that we can avoid exposing the definition of struct clk if we
>> dynamically allocate stuff. One can use struct clk_hw_init to
>> statically initialize data, or instead rely on direct calls to
>> clk_register with a bunch of parameters.
> Which means if you make a mistake in specifying parents for example, it will
> only fail at runtime, possibly before any console is active. With static
> initialization, this will fail at compiletime. Much easier to debug.
Is this really a problem? Once you have good data it does not change.
Debugging bad data when introducing a new chip is just a fact of
life. Static versus dynamic is irrelevant here.
>> Another point is that copying the data at registration-time makes
>> __initdata possible. I haven't done the math yet to see if this
>> really makes a difference. However if we start doing single zImage's
>> with multiple different ARM SoCs then this could recover some pages.
> On the other hand most clock structures are small, so there will be internal
> fragmentation. Also the arrays of parent clock pointers can be shared between
> different clocks. We have about 70 muxes in Tegra30 and 12 different parent
What is missing from struct clk_hw_init to do what your static arrays do today?
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