Re: [RESEND PATCH 4/8] clk: core: support clocks which requires parents on (part 2)

[Dong Aisheng]

Hi Mike,

On Fri, Jun 24, 2016 at 04:52:59PM -0700, Michael Turquette wrote:
> Hi Dong,
> 
> Quoting Dong Aisheng (2016-04-20 02:34:36)
> > On Freescale i.MX7D platform, all clocks operations, including
> > enable/disable, rate change and re-parent, requires its parent clock on.
> > Current clock core can not support it well.
> > This patch adding flag CLK_OPS_PARENT_ON to handle this special case in
> > clock core that enable its parent clock firstly for each operation and
> > disable it later after operation complete.
> > 
> > The patch part 2 fixes set clock rate and set parent while its parent
> > is off. The most special case is for set_parent() operation which requires
> > all parents including both old and new one to be enabled at the same time
> > during the operation.
> > 
> > Cc: Michael Turquette <mturquette@xxxxxxxxxxxx>
> > Cc: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
> > Cc: Shawn Guo <shawnguo@xxxxxxxxxx>
> > Signed-off-by: Dong Aisheng <aisheng.dong@xxxxxxx>
> > ---
> >  drivers/clk/clk.c | 45 ++++++++++++++++++++++++++++-----------------
> >  1 file changed, 28 insertions(+), 17 deletions(-)
> > 
> > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> > index 1f054d1a..d6cef61 100644
> > --- a/drivers/clk/clk.c
> > +++ b/drivers/clk/clk.c
> > @@ -1174,7 +1174,7 @@ static struct clk_core *__clk_set_parent_before(struct clk_core *core,
> >         struct clk_core *old_parent = core->parent;
> >  
> >         /*
> > -        * Migrate prepare state between parents and prevent race with
> > +        * 1. Migrate prepare state between parents and prevent race with
> >          * clk_enable().
> >          *
> >          * If the clock is not prepared, then a race with
> > @@ -1189,13 +1189,16 @@ static struct clk_core *__clk_set_parent_before(struct clk_core *core,
> >          * hardware and software states.
> >          *
> >          * See also: Comment for clk_set_parent() below.
> > +        *
> > +        * 2. enable parent clocks for CLK_OPS_PARENT_ON clock
> >          */
> > -       if (core->prepare_count) {
> > -               clk_core_prepare(parent);
> > -               flags = clk_enable_lock();
> > -               clk_core_enable(parent);
> > -               clk_core_enable(core);
> > -               clk_enable_unlock(flags);
> > +       if (core->prepare_count || core->flags & CLK_OPS_PARENT_ON) {
> > +               clk_core_prepare_enable(parent);
> > +               if (core->prepare_count)
> > +                       clk_core_enable_lock(core);
> > +               else
> > +                       clk_core_prepare_enable(old_parent);
> 
> It took me a few seconds to figure out what I was looking at. The
> set_parent stuff is tricky enough already ... I think we should keep the
> state machine logic very simple. How about:
> 
> 	/* enable old_parent & parent if CLK_OPS_PARENT_ENABLE is set */
> 	if (core->flags & CLK_OPS_PARENT_ENABLE) {
> 		clk_core_prepare_enable(old_parent);
> 		clk_core_prepare_enable(parent);
> 	}
> 
> 	/* migrate prepare count if > 0 */
> 	if (core->prepare_count) {
> 		clk_core_prepare_enable(parent);
> 		clk_core_enable_lock(core);
> 	}
> 

Great suggestion! That looks much clearer.
Will update it in V2.

Thanks

Regards
Dong Aisheng

> > +
> >         }
> >  
> >         /* update the clk tree topology */
> > @@ -1210,18 +1213,16 @@ static void __clk_set_parent_after(struct clk_core *core,
> >                                    struct clk_core *parent,
> >                                    struct clk_core *old_parent)
> >  {
> > -       unsigned long flags;
> > -
> >         /*
> >          * Finish the migration of prepare state and undo the changes done
> >          * for preventing a race with clk_enable().
> >          */
> > -       if (core->prepare_count) {
> > -               flags = clk_enable_lock();
> > -               clk_core_disable(core);
> > -               clk_core_disable(old_parent);
> > -               clk_enable_unlock(flags);
> > -               clk_core_unprepare(old_parent);
> > +       if (core->prepare_count || core->flags & CLK_OPS_PARENT_ON) {
> > +               clk_core_disable_unprepare(old_parent);
> > +               if (core->prepare_count)
> > +                       clk_core_disable_lock(core);
> > +               else
> > +                       clk_core_disable_unprepare(parent);
> 
> Similarly, a more readable solution is:
> 
> 	/*
> 	 * Finish the migration of prepare state and undo the changes done
> 	 * for preventing a race with clk_enable().
> 	 */
> 	if (core->prepare_count) {
> 		clk_core_disable_lock(core);
> 		clk_core_disable_unprepare(old_parent);
> 
> 	/* re-balance ref counting if CLK_OPS_PARENT_ENABLE is set */
> 	if (core->flags & CLK_OPS_PARENT_ENABLE) {
> 		clk_core_disable_unprepare(parent);
> 		clk_core_disable_unprepare(old_parent);
> 	}
> 
> >         }
> >  }
> >  
> > @@ -1468,13 +1469,17 @@ static void clk_change_rate(struct clk_core *core)
> >         unsigned long best_parent_rate = 0;
> >         bool skip_set_rate = false;
> >         struct clk_core *old_parent;
> > +       struct clk_core *parent = NULL;
> >  
> >         old_rate = core->rate;
> >  
> > -       if (core->new_parent)
> > +       if (core->new_parent) {
> > +               parent = core->new_parent;
> >                 best_parent_rate = core->new_parent->rate;
> > -       else if (core->parent)
> > +       } else if (core->parent) {
> > +               parent = core->parent;
> >                 best_parent_rate = core->parent->rate;
> > +       }
> >  
> >         if (core->flags & CLK_SET_RATE_UNGATE) {
> >                 unsigned long flags;
> > @@ -1504,6 +1509,9 @@ static void clk_change_rate(struct clk_core *core)
> >  
> >         trace_clk_set_rate(core, core->new_rate);
> >  
> > +       if (core->flags & CLK_OPS_PARENT_ON)
> > +               clk_core_prepare_enable(parent);
> > +
> >         if (!skip_set_rate && core->ops->set_rate)
> >                 core->ops->set_rate(core->hw, core->new_rate, best_parent_rate);
> >  
> > @@ -1520,6 +1528,9 @@ static void clk_change_rate(struct clk_core *core)
> >                 clk_core_unprepare(core);
> >         }
> >  
> > +       if (core->flags & CLK_OPS_PARENT_ON)
> > +               clk_core_disable_unprepare(parent);
> > +
> 
> This part looks good to me.
> 
> Regards,
> Mike
> 
> >         if (core->notifier_count && old_rate != core->rate)
> >                 __clk_notify(core, POST_RATE_CHANGE, old_rate, core->rate);
> >  
> > -- 
> > 1.9.1
> > 
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