[PATCH 2/2] clk: initial clock driver for TWL6030

Mark Brown broonie at kernel.org
Thu Jul 31 04:05:31 PDT 2014

On Thu, Jul 31, 2014 at 11:56:15AM +0200, Stefan Assmann wrote:
> On 30.07.2014 19:50, Mark Brown wrote:
> > On Wed, Jul 30, 2014 at 04:02:29PM +0200, Stefan Assmann wrote:

> >> +static int twl6030_clk32kg_is_prepared(struct clk_hw *hw)
> >> +{
> >> +	struct twl6030_desc *desc = to_twl6030_desc(hw);
> >> +
> >> +	return desc->enabled;
> >> +}

> > Why not just check the register map - can't the register be cached?  If
> > that's not possible a comment would be good.

> I just took atl_clk_is_enabled() as template. If you say it's better
> to read the value, that can be arranged.

It might be worth doing this if you have to go to hardware to check the
status, if you can read a cache then just using the register is less
error prone.

> >> +	else
> >> +		clk_prepare(clk);

> > Why is the clock driver defaulting to enabling the clock, and if it
> > needs to shouldn't it be doing a prepere_enable() even if the enable
> > happens not to do anything to the hardware?  Otherwise child clocks
> > might get confused.

> Mike advised me to convert the functions from enable/disable to
> prepare/unprepare because i2c transactions may sleep. That's what I did.
> The code no longer enables the clock and just prepares it. So IIUC the
> call to clk_prepare() should be fine.

That's not going to help consumers of the clock, you do need to move the
operations to prepare() but users shouldn't need to know what happens in
prepare() and what happens in enable().

You've also not addressed the comment about defaulting to enabling the
clock in the first place.
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