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[v2,2/5] clk: bcm281xx: implement prerequisite clocks

Message ID 20140524005358.23136.8918@quantum
State New
Headers show

Commit Message

Mike Turquette May 24, 2014, 12:53 a.m. UTC
Quoting Alex Elder (2014-05-20 05:52:39)
> @@ -743,11 +746,16 @@ struct clk *kona_clk_setup(struct kona_clk *bcm_clk)
>         clk = clk_register(NULL, &bcm_clk->hw);
>         if (IS_ERR(clk)) {
>                 pr_err("%s: error registering clock %s (%ld)\n", __func__,
> -                       init_data->name, PTR_ERR(clk));
> +                       name, PTR_ERR(clk));
>                 goto out_teardown;
>         }
>         BUG_ON(!clk);
>  
> +       /*  Make it so we can look the clock up using clk_find() */

s/clk_find/clk_get/ ?

> +       bcm_clk->cl.con_id = name;
> +       bcm_clk->cl.clk = clk;
> +       clkdev_add(&bcm_clk->cl);

This is not so nice. I'll explain more below.

> +
>         return clk;
>  out_teardown:
>         bcm_clk_teardown(bcm_clk);
> diff --git a/drivers/clk/bcm/clk-kona.c b/drivers/clk/bcm/clk-kona.c
> index d8a7f38..fd070d6 100644
> --- a/drivers/clk/bcm/clk-kona.c
> +++ b/drivers/clk/bcm/clk-kona.c
> @@ -1195,6 +1195,48 @@ static bool __peri_clk_init(struct kona_clk *bcm_clk)
>         return true;
>  }
>  
> +static bool __kona_clk_init(struct kona_clk *bcm_clk);
> +static bool __kona_prereq_init(struct kona_clk *bcm_clk)
> +{
> +       struct clk *clk;
> +       struct clk_hw *hw;
> +       struct kona_clk *prereq;
> +
> +       BUG_ON(clk_is_initialized(bcm_clk));
> +
> +       if (!bcm_clk->p.prereq)
> +               return true;
> +
> +       clk = clk_get(NULL, bcm_clk->p.prereq);

The clkdev global namespace is getting polluted with all of these new
prereq clocks. If there was an associated struct device *dev with them
then it wouldn't be a problem, but you might get collisions with other
clock drivers that also use NULL for the device.

It would be a lot nicer for the clocks that require a prereq clock to
just use clk_get(dev, "well_known_name"); in the same way that drivers
use it, without considering it a special case.

> +       if (IS_ERR(clk)) {
> +               pr_err("%s: unable to get prereq clock %s for %s\n",
> +                       __func__, bcm_clk->p.prereq, bcm_clk->init_data.name);
> +               return false;
> +       }
> +       hw = __clk_get_hw(clk);
> +       if (!hw) {
> +               pr_err("%s: null hw pointer for clock %s\n", __func__,
> +                       bcm_clk->init_data.name);
> +               return false;
> +       }
> +       prereq = to_kona_clk(hw);
> +       if (prereq->ccu != bcm_clk->ccu) {
> +               pr_err("%s: prereq clock %s CCU different for clock %s\n",
> +                       __func__, bcm_clk->p.prereq, bcm_clk->init_data.name);
> +               return false;
> +       }
> +
> +       /* Initialize the prerequisite clock first */
> +       if (!__kona_clk_init(prereq)) {
> +               pr_err("%s: failed to init prereq %s for clock %s\n",
> +                       __func__, bcm_clk->p.prereq, bcm_clk->init_data.name);
> +               return false;
> +       }
> +       bcm_clk->p.prereq_clk = clk;

The above seems like a lot effort to go to. Why not skip all of this and
just implement the prerequisite logic in the .enable & .disable
callbacks? E.g. your kona clk .enable callback would look like:



I guess it might take some trickery to get clk_get to work like that.
Let me know if I've completely lost the plot.

Regards,
Mike
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Comments

Alex Elder May 29, 2014, 1:26 p.m. UTC | #1
On 05/23/2014 07:53 PM, Mike Turquette wrote:
> Quoting Alex Elder (2014-05-20 05:52:39)
>> @@ -743,11 +746,16 @@ struct clk *kona_clk_setup(struct kona_clk *bcm_clk)
>>         clk = clk_register(NULL, &bcm_clk->hw);
>>         if (IS_ERR(clk)) {
>>                 pr_err("%s: error registering clock %s (%ld)\n", __func__,
>> -                       init_data->name, PTR_ERR(clk));
>> +                       name, PTR_ERR(clk));
>>                 goto out_teardown;
>>         }
>>         BUG_ON(!clk);
>>  
>> +       /*  Make it so we can look the clock up using clk_find() */
> 
> s/clk_find/clk_get/ ?

Yes, this is a mistake.

> 
>> +       bcm_clk->cl.con_id = name;
>> +       bcm_clk->cl.clk = clk;
>> +       clkdev_add(&bcm_clk->cl);
> 
> This is not so nice. I'll explain more below.

Actually, this code is no longer needed at all.  It was
at one time, but I evolved away from that need, and never
noticed that this remnant remained.  I will delete it.

I'm really sorry I missed that, it was confusing for
it to still be there I'm sure.

>> +
>>         return clk;
>>  out_teardown:
>>         bcm_clk_teardown(bcm_clk);
>> diff --git a/drivers/clk/bcm/clk-kona.c b/drivers/clk/bcm/clk-kona.c
>> index d8a7f38..fd070d6 100644
>> --- a/drivers/clk/bcm/clk-kona.c
>> +++ b/drivers/clk/bcm/clk-kona.c
>> @@ -1195,6 +1195,48 @@ static bool __peri_clk_init(struct kona_clk *bcm_clk)
>>         return true;
>>  }
>>  
>> +static bool __kona_clk_init(struct kona_clk *bcm_clk);
>> +static bool __kona_prereq_init(struct kona_clk *bcm_clk)
>> +{
>> +       struct clk *clk;
>> +       struct clk_hw *hw;
>> +       struct kona_clk *prereq;
>> +
>> +       BUG_ON(clk_is_initialized(bcm_clk));
>> +
>> +       if (!bcm_clk->p.prereq)
>> +               return true;
>> +
>> +       clk = clk_get(NULL, bcm_clk->p.prereq);
> 
> The clkdev global namespace is getting polluted with all of these new
> prereq clocks. If there was an associated struct device *dev with them
> then it wouldn't be a problem, but you might get collisions with other
> clock drivers that also use NULL for the device.

Again, you caught a confusing mistake.  The clk_lookup
structure will go away.

> It would be a lot nicer for the clocks that require a prereq clock to
> just use clk_get(dev, "well_known_name"); in the same way that drivers
> use it, without considering it a special case.

That is in fact what happens, in __kona_prereq_init().

>> +       if (IS_ERR(clk)) {
>> +               pr_err("%s: unable to get prereq clock %s for %s\n",
>> +                       __func__, bcm_clk->p.prereq, bcm_clk->init_data.name);
>> +               return false;
>> +       }
>> +       hw = __clk_get_hw(clk);
>> +       if (!hw) {
>> +               pr_err("%s: null hw pointer for clock %s\n", __func__,
>> +                       bcm_clk->init_data.name);
>> +               return false;
>> +       }
>> +       prereq = to_kona_clk(hw);
>> +       if (prereq->ccu != bcm_clk->ccu) {
>> +               pr_err("%s: prereq clock %s CCU different for clock %s\n",
>> +                       __func__, bcm_clk->p.prereq, bcm_clk->init_data.name);
>> +               return false;
>> +       }
>> +
>> +       /* Initialize the prerequisite clock first */
>> +       if (!__kona_clk_init(prereq)) {
>> +               pr_err("%s: failed to init prereq %s for clock %s\n",
>> +                       __func__, bcm_clk->p.prereq, bcm_clk->init_data.name);
>> +               return false;
>> +       }
>> +       bcm_clk->p.prereq_clk = clk;
> 
> The above seems like a lot effort to go to. Why not skip all of this and
> just implement the prerequisite logic in the .enable & .disable
> callbacks? E.g. your kona clk .enable callback would look like:

I think the problem is that it means the clock consumers
would have to know that prerequisite relationship.  And
that is dependent on the clock tree.  The need for it in
this case was because the boot loader didn't initialize
all the clocks that were needed.  If we could count on
the boot loader setting things up initially we might not
need to do this.

> 
> diff --git a/drivers/clk/bcm/clk-kona.c b/drivers/clk/bcm/clk-kona.c
> index d603c4e..51f35b4 100644
> --- a/drivers/clk/bcm/clk-kona.c
> +++ b/drivers/clk/bcm/clk-kona.c
> @@ -987,6 +987,12 @@ static int kona_peri_clk_enable(struct clk_hw *hw)
>  {
>  	struct kona_clk *bcm_clk = to_kona_clk(hw);
>  	struct bcm_clk_gate *gate = &bcm_clk->u.peri->gate;
> +	int ret;
> +
> +	hw->prereq_bus_clk = clk_get(hw->ccu, hw->prereq);
> +	ret = clk_enable(prereq_bus_clk);
> +	if (ret)
> +		return ret;
>  
>  	return clk_gate(bcm_clk->ccu, bcm_clk->init_data.name, gate, true);
>  }
> @@ -997,6 +1003,9 @@ static void kona_peri_clk_disable(struct clk_hw *hw)
>  	struct bcm_clk_gate *gate = &bcm_clk->u.peri->gate;
>  
>  	(void)clk_gate(bcm_clk->ccu, bcm_clk->init_data.name, gate, false);
> +
> +	clk_disable(hw->prereq_bus_clk);
> +	clk_put(hw->prereq_bus_clk);
>  }
>  
>  static int kona_peri_clk_is_enabled(struct clk_hw *hw)
> 
> 
> I guess it might take some trickery to get clk_get to work like that.
> Let me know if I've completely lost the plot.

I don't think so, but I think there's a lot of stuff
here to try to understand, and you're trying to extract
it from the code without the benefit of some background
of how and why it's done this way.

Hopefully all this verbiage is moving you closer to
understanding...  I appreciate your patience.

					-Alex

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Mike Turquette May 29, 2014, 4:35 p.m. UTC | #2
Quoting Alex Elder (2014-05-29 06:26:15)
> On 05/23/2014 07:53 PM, Mike Turquette wrote:
> > The above seems like a lot effort to go to. Why not skip all of this and
> > just implement the prerequisite logic in the .enable & .disable
> > callbacks? E.g. your kona clk .enable callback would look like:
> 
> I think the problem is that it means the clock consumers
> would have to know that prerequisite relationship.  And
> that is dependent on the clock tree.  The need for it in
> this case was because the boot loader didn't initialize
> all the clocks that were needed.  If we could count on
> the boot loader setting things up initially we might not
> need to do this.
> 
> > 
> > diff --git a/drivers/clk/bcm/clk-kona.c b/drivers/clk/bcm/clk-kona.c
> > index d603c4e..51f35b4 100644
> > --- a/drivers/clk/bcm/clk-kona.c
> > +++ b/drivers/clk/bcm/clk-kona.c
> > @@ -987,6 +987,12 @@ static int kona_peri_clk_enable(struct clk_hw *hw)
> >  {
> >       struct kona_clk *bcm_clk = to_kona_clk(hw);
> >       struct bcm_clk_gate *gate = &bcm_clk->u.peri->gate;
> > +     int ret;
> > +
> > +     hw->prereq_bus_clk = clk_get(hw->ccu, hw->prereq);
> > +     ret = clk_enable(prereq_bus_clk);
> > +     if (ret)
> > +             return ret;
> >  
> >       return clk_gate(bcm_clk->ccu, bcm_clk->init_data.name, gate, true);
> >  }
> > @@ -997,6 +1003,9 @@ static void kona_peri_clk_disable(struct clk_hw *hw)
> >       struct bcm_clk_gate *gate = &bcm_clk->u.peri->gate;
> >  
> >       (void)clk_gate(bcm_clk->ccu, bcm_clk->init_data.name, gate, false);
> > +
> > +     clk_disable(hw->prereq_bus_clk);
> > +     clk_put(hw->prereq_bus_clk);
> >  }
> >  
> >  static int kona_peri_clk_is_enabled(struct clk_hw *hw)
> > 
> > 
> > I guess it might take some trickery to get clk_get to work like that.
> > Let me know if I've completely lost the plot.
> 
> I don't think so, but I think there's a lot of stuff
> here to try to understand, and you're trying to extract
> it from the code without the benefit of some background
> of how and why it's done this way.
> 
> Hopefully all this verbiage is moving you closer to
> understanding...  I appreciate your patience.

Hi Alex,

Can you comment on my diff above? I basically tossed up some pseudo-code
to show how clk_enable calls can be nested inside of each other. I'd
like to know if that approach makes sense for your prereq clocks case.

Note that Linux device drivers that consume leaf clocks do NOT need to
know about the prereq clocks. All of that prereq clock knowledge is
stored in the .enable callback for the leaf clock (see above).

Regards,
Mike

> 
>                                         -Alex
> 
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Alex Elder May 29, 2014, 4:53 p.m. UTC | #3
On 05/29/2014 11:35 AM, Mike Turquette wrote:
> Quoting Alex Elder (2014-05-29 06:26:15)
>> On 05/23/2014 07:53 PM, Mike Turquette wrote:
>>> The above seems like a lot effort to go to. Why not skip all of this and
>>> just implement the prerequisite logic in the .enable & .disable
>>> callbacks? E.g. your kona clk .enable callback would look like:
>>
>> I think the problem is that it means the clock consumers
>> would have to know that prerequisite relationship.  And
>> that is dependent on the clock tree.  The need for it in
>> this case was because the boot loader didn't initialize
>> all the clocks that were needed.  If we could count on
>> the boot loader setting things up initially we might not
>> need to do this.

I think you've convinced me that if the prerequisite is
set up at initialization time, the consumers don't need
to know about the the clock tree.

>>>
>>> diff --git a/drivers/clk/bcm/clk-kona.c b/drivers/clk/bcm/clk-kona.c
>>> index d603c4e..51f35b4 100644
>>> --- a/drivers/clk/bcm/clk-kona.c
>>> +++ b/drivers/clk/bcm/clk-kona.c
>>> @@ -987,6 +987,12 @@ static int kona_peri_clk_enable(struct clk_hw *hw)
>>>  {
>>>       struct kona_clk *bcm_clk = to_kona_clk(hw);
>>>       struct bcm_clk_gate *gate = &bcm_clk->u.peri->gate;
>>> +     int ret;
>>> +
>>> +     hw->prereq_bus_clk = clk_get(hw->ccu, hw->prereq);
>>> +     ret = clk_enable(prereq_bus_clk);
>>> +     if (ret)
>>> +             return ret;
>>>  
>>>       return clk_gate(bcm_clk->ccu, bcm_clk->init_data.name, gate, true);
>>>  }
>>> @@ -997,6 +1003,9 @@ static void kona_peri_clk_disable(struct clk_hw *hw)
>>>       struct bcm_clk_gate *gate = &bcm_clk->u.peri->gate;
>>>  
>>>       (void)clk_gate(bcm_clk->ccu, bcm_clk->init_data.name, gate, false);
>>> +
>>> +     clk_disable(hw->prereq_bus_clk);
>>> +     clk_put(hw->prereq_bus_clk);
>>>  }
>>>  
>>>  static int kona_peri_clk_is_enabled(struct clk_hw *hw)
>>>
>>>
>>> I guess it might take some trickery to get clk_get to work like that.
>>> Let me know if I've completely lost the plot.
>>
>> I don't think so, but I think there's a lot of stuff
>> here to try to understand, and you're trying to extract
>> it from the code without the benefit of some background
>> of how and why it's done this way.
>>
>> Hopefully all this verbiage is moving you closer to
>> understanding...  I appreciate your patience.
> 
> Hi Alex,
> 
> Can you comment on my diff above? I basically tossed up some pseudo-code
> to show how clk_enable calls can be nested inside of each other. I'd
> like to know if that approach makes sense for your prereq clocks case.

Yes, I should have looked more closely before.

Are you suggesting this prerequisite notion get elevated into the
common framework?  Or is "hw" here just representative of the
Kona-specific clock structure?

In any case, you're suggesting the prerequisite be handled in the
enable path (as opposed to the one-time initialization path),
which during the course of this discussion I've been thinking may
be the right way to do it.

Let me see if I can rework it that way and I'll let you know
what I discover as a result.  I hope to have something to
talk about later today.

Thanks a lot Mike.

					-Alex

> Note that Linux device drivers that consume leaf clocks do NOT need to
> know about the prereq clocks. All of that prereq clock knowledge is
> stored in the .enable callback for the leaf clock (see above).
> 
> Regards,
> Mike
> 
>>
>>                                         -Alex
>>

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Mike Turquette May 29, 2014, 5:47 p.m. UTC | #4
Quoting Alex Elder (2014-05-29 09:53:50)
> On 05/29/2014 11:35 AM, Mike Turquette wrote:
> > Quoting Alex Elder (2014-05-29 06:26:15)
> >> On 05/23/2014 07:53 PM, Mike Turquette wrote:
> >>> The above seems like a lot effort to go to. Why not skip all of this and
> >>> just implement the prerequisite logic in the .enable & .disable
> >>> callbacks? E.g. your kona clk .enable callback would look like:
> >>
> >> I think the problem is that it means the clock consumers
> >> would have to know that prerequisite relationship.  And
> >> that is dependent on the clock tree.  The need for it in
> >> this case was because the boot loader didn't initialize
> >> all the clocks that were needed.  If we could count on
> >> the boot loader setting things up initially we might not
> >> need to do this.
> 
> I think you've convinced me that if the prerequisite is
> set up at initialization time, the consumers don't need
> to know about the the clock tree.
> 
> >>>
> >>> diff --git a/drivers/clk/bcm/clk-kona.c b/drivers/clk/bcm/clk-kona.c
> >>> index d603c4e..51f35b4 100644
> >>> --- a/drivers/clk/bcm/clk-kona.c
> >>> +++ b/drivers/clk/bcm/clk-kona.c
> >>> @@ -987,6 +987,12 @@ static int kona_peri_clk_enable(struct clk_hw *hw)
> >>>  {
> >>>       struct kona_clk *bcm_clk = to_kona_clk(hw);
> >>>       struct bcm_clk_gate *gate = &bcm_clk->u.peri->gate;
> >>> +     int ret;
> >>> +
> >>> +     hw->prereq_bus_clk = clk_get(hw->ccu, hw->prereq);
> >>> +     ret = clk_enable(prereq_bus_clk);
> >>> +     if (ret)
> >>> +             return ret;
> >>>  
> >>>       return clk_gate(bcm_clk->ccu, bcm_clk->init_data.name, gate, true);
> >>>  }
> >>> @@ -997,6 +1003,9 @@ static void kona_peri_clk_disable(struct clk_hw *hw)
> >>>       struct bcm_clk_gate *gate = &bcm_clk->u.peri->gate;
> >>>  
> >>>       (void)clk_gate(bcm_clk->ccu, bcm_clk->init_data.name, gate, false);
> >>> +
> >>> +     clk_disable(hw->prereq_bus_clk);
> >>> +     clk_put(hw->prereq_bus_clk);
> >>>  }
> >>>  
> >>>  static int kona_peri_clk_is_enabled(struct clk_hw *hw)
> >>>
> >>>
> >>> I guess it might take some trickery to get clk_get to work like that.
> >>> Let me know if I've completely lost the plot.
> >>
> >> I don't think so, but I think there's a lot of stuff
> >> here to try to understand, and you're trying to extract
> >> it from the code without the benefit of some background
> >> of how and why it's done this way.
> >>
> >> Hopefully all this verbiage is moving you closer to
> >> understanding...  I appreciate your patience.
> > 
> > Hi Alex,
> > 
> > Can you comment on my diff above? I basically tossed up some pseudo-code
> > to show how clk_enable calls can be nested inside of each other. I'd
> > like to know if that approach makes sense for your prereq clocks case.
> 
> Yes, I should have looked more closely before.
> 
> Are you suggesting this prerequisite notion get elevated into the
> common framework?

Nope.

> Or is "hw" here just representative of the
> Kona-specific clock structure?

Yup. It's just good old struct clk_hw. There is one instance of this
struct for every struct clk object.

> 
> In any case, you're suggesting the prerequisite be handled in the
> enable path (as opposed to the one-time initialization path),
> which during the course of this discussion I've been thinking may
> be the right way to do it.

Right, and don't forget that you have both the prepare path AND the
enable path. It is common for drivers to call clk_prepare once at probe
time and then aggressively call clk_enable/clk_disable for fine-grained
PM. Likewise some drivers always use clk_prepare_enable and
clk_disable_unprepare.

The point is that you have two callbacks that you might split some of
this stuff across. Your "initializiation" stuff might go into .prepare()
and simply enabling the clock might go into .enable().

> 
> Let me see if I can rework it that way and I'll let you know
> what I discover as a result.  I hope to have something to
> talk about later today.

Sounds good.

Regards,
Mike

> 
> Thanks a lot Mike.
> 
>                                         -Alex
> 
> > Note that Linux device drivers that consume leaf clocks do NOT need to
> > know about the prereq clocks. All of that prereq clock knowledge is
> > stored in the .enable callback for the leaf clock (see above).
> > 
> > Regards,
> > Mike
> > 
> >>
> >>                                         -Alex
> >>
> 
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Alex Elder May 30, 2014, 3:20 a.m. UTC | #5
On 05/23/2014 07:53 PM, Mike Turquette wrote:
> Quoting Alex Elder (2014-05-20 05:52:39)
>> @@ -743,11 +746,16 @@ struct clk *kona_clk_setup(struct kona_clk *bcm_clk)
>>         clk = clk_register(NULL, &bcm_clk->hw);
>>         if (IS_ERR(clk)) {
>>                 pr_err("%s: error registering clock %s (%ld)\n", __func__,
>> -                       init_data->name, PTR_ERR(clk));
>> +                       name, PTR_ERR(clk));
>>                 goto out_teardown;
>>         }
>>         BUG_ON(!clk);
>>  
>> +       /*  Make it so we can look the clock up using clk_find() */
> 
> s/clk_find/clk_get/ ?
> 
>> +       bcm_clk->cl.con_id = name;
>> +       bcm_clk->cl.clk = clk;
>> +       clkdev_add(&bcm_clk->cl);
> 
> This is not so nice. I'll explain more below.

OK, despite what I said before, I do need this, or
something like it, so I can look up clocks by name.
(Continued below.)

> 
>> +
>>         return clk;
>>  out_teardown:
>>         bcm_clk_teardown(bcm_clk);
>> diff --git a/drivers/clk/bcm/clk-kona.c b/drivers/clk/bcm/clk-kona.c
>> index d8a7f38..fd070d6 100644
>> --- a/drivers/clk/bcm/clk-kona.c
>> +++ b/drivers/clk/bcm/clk-kona.c
>> @@ -1195,6 +1195,48 @@ static bool __peri_clk_init(struct kona_clk *bcm_clk)
>>         return true;
>>  }
>>  
>> +static bool __kona_clk_init(struct kona_clk *bcm_clk);
>> +static bool __kona_prereq_init(struct kona_clk *bcm_clk)
>> +{
>> +       struct clk *clk;
>> +       struct clk_hw *hw;
>> +       struct kona_clk *prereq;
>> +
>> +       BUG_ON(clk_is_initialized(bcm_clk));
>> +
>> +       if (!bcm_clk->p.prereq)
>> +               return true;
>> +
>> +       clk = clk_get(NULL, bcm_clk->p.prereq);
> 
> The clkdev global namespace is getting polluted with all of these new
> prereq clocks. If there was an associated struct device *dev with them
> then it wouldn't be a problem, but you might get collisions with other
> clock drivers that also use NULL for the device.

Yes I recognize this.  Ideally a CCU would have a device struct
associated with it that I could use, because the name of a clock
is unique within that context.  But I have no such device available.
(Please correct me if I'm wrong.  I don't want to make one up, and
I would like to use it if it exists.)

> It would be a lot nicer for the clocks that require a prereq clock to
> just use clk_get(dev, "well_known_name"); in the same way that drivers
> use it, without considering it a special case.

I can do something like that if I can get a meaningful device
structure.  Do you have any suggestions?

Other than this issue, I've implemented all of the previous
initialization routines using ->prepare() instead, and it
works fine.  I'm going to send an updated series out tomorrow.
I want to look it over again after a good night's sleep...

					-Alex

>> +       if (IS_ERR(clk)) {
>> +               pr_err("%s: unable to get prereq clock %s for %s\n",
>> +                       __func__, bcm_clk->p.prereq, bcm_clk->init_data.name);
>> +               return false;
>> +       }
>> +       hw = __clk_get_hw(clk);
>> +       if (!hw) {
>> +               pr_err("%s: null hw pointer for clock %s\n", __func__,
>> +                       bcm_clk->init_data.name);
>> +               return false;
>> +       }
>> +       prereq = to_kona_clk(hw);
>> +       if (prereq->ccu != bcm_clk->ccu) {
>> +               pr_err("%s: prereq clock %s CCU different for clock %s\n",
>> +                       __func__, bcm_clk->p.prereq, bcm_clk->init_data.name);
>> +               return false;
>> +       }
>> +
>> +       /* Initialize the prerequisite clock first */
>> +       if (!__kona_clk_init(prereq)) {
>> +               pr_err("%s: failed to init prereq %s for clock %s\n",
>> +                       __func__, bcm_clk->p.prereq, bcm_clk->init_data.name);
>> +               return false;
>> +       }
>> +       bcm_clk->p.prereq_clk = clk;
> 
> The above seems like a lot effort to go to. Why not skip all of this and
> just implement the prerequisite logic in the .enable & .disable
> callbacks? E.g. your kona clk .enable callback would look like:
> 
> diff --git a/drivers/clk/bcm/clk-kona.c b/drivers/clk/bcm/clk-kona.c
> index d603c4e..51f35b4 100644
> --- a/drivers/clk/bcm/clk-kona.c
> +++ b/drivers/clk/bcm/clk-kona.c
> @@ -987,6 +987,12 @@ static int kona_peri_clk_enable(struct clk_hw *hw)
>  {
>  	struct kona_clk *bcm_clk = to_kona_clk(hw);
>  	struct bcm_clk_gate *gate = &bcm_clk->u.peri->gate;
> +	int ret;
> +
> +	hw->prereq_bus_clk = clk_get(hw->ccu, hw->prereq);
> +	ret = clk_enable(prereq_bus_clk);
> +	if (ret)
> +		return ret;
>  
>  	return clk_gate(bcm_clk->ccu, bcm_clk->init_data.name, gate, true);
>  }
> @@ -997,6 +1003,9 @@ static void kona_peri_clk_disable(struct clk_hw *hw)
>  	struct bcm_clk_gate *gate = &bcm_clk->u.peri->gate;
>  
>  	(void)clk_gate(bcm_clk->ccu, bcm_clk->init_data.name, gate, false);
> +
> +	clk_disable(hw->prereq_bus_clk);
> +	clk_put(hw->prereq_bus_clk);
>  }
>  
>  static int kona_peri_clk_is_enabled(struct clk_hw *hw)
> 
> 
> I guess it might take some trickery to get clk_get to work like that.
> Let me know if I've completely lost the plot.
> 
> Regards,
> Mike
> 

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Alex Elder May 30, 2014, 2:05 p.m. UTC | #6
On 05/29/2014 10:20 PM, Alex Elder wrote:
> On 05/23/2014 07:53 PM, Mike Turquette wrote:
>> Quoting Alex Elder (2014-05-20 05:52:39)
>>> @@ -743,11 +746,16 @@ struct clk *kona_clk_setup(struct kona_clk *bcm_clk)
>>>         clk = clk_register(NULL, &bcm_clk->hw);
>>>         if (IS_ERR(clk)) {
>>>                 pr_err("%s: error registering clock %s (%ld)\n", __func__,
>>> -                       init_data->name, PTR_ERR(clk));
>>> +                       name, PTR_ERR(clk));
>>>                 goto out_teardown;
>>>         }
>>>         BUG_ON(!clk);
>>>  
>>> +       /*  Make it so we can look the clock up using clk_find() */
>>
>> s/clk_find/clk_get/ ?
>>
>>> +       bcm_clk->cl.con_id = name;
>>> +       bcm_clk->cl.clk = clk;
>>> +       clkdev_add(&bcm_clk->cl);
>>
>> This is not so nice. I'll explain more below.
> 
> OK, despite what I said before, I do need this, or
> something like it, so I can look up clocks by name.
> (Continued below.)
...

I've been thinking this morning about ways to at least
improve this.  The problem is worse than just prerequisite
clocks polluting the global name space.  Right now *all*
clocks get their name registered this way, because any one
of them could be tagged as a prerequisite, and therefore
in need of lookup by name.

If I had a device structure to associate the clock names
with it would help, but I don't have one.  There is no
other way to define a separate name space, it's either
associated with a device, or it's global.

Given all that, I could prefix or suffix the clock names
with some special string, in order to sort of carve out a
reserved portion of the global name space.

I could specify the prerequisite clock by its index in
its CCU's clocks array.  I could then manufacture a
of_phandle_args structure and use of_clk_get_from_provider()
to look up what we need, but that seems kind of kludgy.
Maybe a new function could encapsulate the messy details
of that.

Do you have any suggestions?  I can create some new
common code if appropriate, but only if it represents
missing functionality that's generally useful.

					-Alex


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diff mbox

Patch

diff --git a/drivers/clk/bcm/clk-kona.c b/drivers/clk/bcm/clk-kona.c
index d603c4e..51f35b4 100644
--- a/drivers/clk/bcm/clk-kona.c
+++ b/drivers/clk/bcm/clk-kona.c
@@ -987,6 +987,12 @@  static int kona_peri_clk_enable(struct clk_hw *hw)
 {
 	struct kona_clk *bcm_clk = to_kona_clk(hw);
 	struct bcm_clk_gate *gate = &bcm_clk->u.peri->gate;
+	int ret;
+
+	hw->prereq_bus_clk = clk_get(hw->ccu, hw->prereq);
+	ret = clk_enable(prereq_bus_clk);
+	if (ret)
+		return ret;
 
 	return clk_gate(bcm_clk->ccu, bcm_clk->init_data.name, gate, true);
 }
@@ -997,6 +1003,9 @@  static void kona_peri_clk_disable(struct clk_hw *hw)
 	struct bcm_clk_gate *gate = &bcm_clk->u.peri->gate;
 
 	(void)clk_gate(bcm_clk->ccu, bcm_clk->init_data.name, gate, false);
+
+	clk_disable(hw->prereq_bus_clk);
+	clk_put(hw->prereq_bus_clk);
 }
 
 static int kona_peri_clk_is_enabled(struct clk_hw *hw)