[RFC V2 6/8] ARM i.MX: prepare common clk support

[Richard Zhao]

On Fri, Dec 16, 2011 at 03:34:14PM -0800, Mike Turquette wrote:
> On Wed, Dec 14, 2011 at 1:23 AM, Richard Zhao <richard.zhao at linaro.org> wrote:
> > From: Sascha Hauer <s.hauer at pengutronix.de>
> >
> > Add static clock help macros, clock register spinlock.
> >
> > Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
> > Signed-off-by: Richard Zhao <richard.zhao at linaro.org>
> > ---
> >  arch/arm/plat-mxc/clock.c              |    8 ++++++
> >  arch/arm/plat-mxc/include/mach/clock.h |   42 +++++++++++++++++++++++++++++--
> >  2 files changed, 47 insertions(+), 3 deletions(-)
> >
> ...
> >
> > +extern spinlock_t imx_ccm_lock;
> > +
> > +#define DEFINE_CLK_GATE2B(_name, _parent, _reg, _shift) \
> > +       struct clk_gate2b _name = { \
> > +               .clk = { \
> > +                       .name = #_name, \
> > +                       .ops = &clk_gate2b_ops, \
> > +                       .parent = _parent, \
> > +               }, \
> > +               .reg = (_reg), \
> > +               .shift = (_shift) * 2, \
> > +               .val_en = 0x3, \
> > +               .val_dis = 0x0, \
> > +               .lock = &imx_ccm_lock, \
> > +       }
> > +
> > +#define IMX_DEFINE_CLK_DIVIDER(_name, _parent, _flags, _reg, _shift, _width) \
> > +       DEFINE_CLK_DIVIDER(_name, _parent, _flags, _reg, _shift, _width, \
> > +                       &imx_ccm_lock)
> > +
> > +#define IMX_DEFINE_CLK_MUX(_name, _reg, _shift, _width, _clks) \
> > +       DEFINE_CLK_MUX(_name, _reg, _shift, _width, _clks, &imx_ccm_lock)
> 
> gate2b, basic div and basic mux clks all use the imx_ccm_lock.  How
> many registers are we talking about here?  If the number is very high
> then maybe per-register locking makes sense for you?
per-register/per-register group locking make me feel complicated. How do I group the
registers? and register layout may change for different SoCs.
Considering prepare_lock and enable_lock, only gate register that share with other
non-gate clocks needs a lock. Keeping the rule in mind is strange, and easy to come
with faults.
Another way is to use a global lock. Do normal register read/write in the lock. but for
status busy wait checking, it's read only, we can release the lock temporarily.

Thanks
Richard
> 
> Also, do you need locking added to the basic gated clk type, or any of
> the others?  I'll probably add it anyways but just curious...
I think yes. Give usr an option to use the lock.

Thanks
Richard
> 
> Regards,
> Mike