Re: [PATCH V2] clk: Add composite clock type

[Prashant Gaikwad <pgaikwad@nvidia.com>]

On Wednesday 06 February 2013 03:36 PM, Tomasz Figa wrote:
> On Wednesday 06 of February 2013 08:34:32 Prashant Gaikwad wrote:
>> On Tuesday 05 February 2013 03:45 PM, Tomasz Figa wrote:
>>> Hi Prashant,
>>>
>>> Thank you for your patch. Please see some comments inline.
>>>
>>> On Monday 04 of February 2013 13:41:22 Prashant Gaikwad wrote:
>>>> Not all clocks are required to be decomposed into basic clock
>>>> types but at the same time want to use the functionality
>>>> provided by these basic clock types instead of duplicating.
>>>>
>>>> For example, Tegra SoC has ~100 clocks which can be decomposed
>>>> into Mux -> Div -> Gate clock types making the clock count to
>>>> ~300. Also, parent change operation can not be performed on gate
>>>> clock which forces to use mux clock in driver if want to change
>>>> the parent.
>>>>
>>>> Instead aggregate the basic clock types functionality into one
>>>> clock and just use this clock for all operations. This clock
>>>> type re-uses the functionality of basic clock types and not
>>>> limited to basic clock types but any hardware-specific
>>>> implementation.
>>>>
>>>> Signed-off-by: Prashant Gaikwad <pgaikwad@nvidia.com>
>>>> ---
>>>>
>>>> Changes from V1:
>>>> - 2nd patch dropped as the concept is acked by Mike.
>>>> - Fixed comments from Stephen.
>>>>
>>>> ---
>>>>
>>>>    drivers/clk/Makefile         |    1 +
>>>>    drivers/clk/clk-composite.c  |  208
>>>>
>>>> ++++++++++++++++++++++++++++++++++++++++++
>>>> include/linux/clk-provider.h
>>>>
>>>> |   30 ++++++
>>>>
>>>>    3 files changed, 239 insertions(+), 0 deletions(-)
>>>>    create mode 100644 drivers/clk/clk-composite.c
>>>>
>>>> diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
>>>> index ce77077..2287848 100644
>>>> --- a/drivers/clk/Makefile
>>>> +++ b/drivers/clk/Makefile
>>>> @@ -7,6 +7,7 @@ obj-$(CONFIG_COMMON_CLK)      += clk-fixed-factor.o
>>>>
>>>>    obj-$(CONFIG_COMMON_CLK)     += clk-fixed-rate.o
>>>>    obj-$(CONFIG_COMMON_CLK)     += clk-gate.o
>>>>    obj-$(CONFIG_COMMON_CLK)     += clk-mux.o
>>>>
>>>> +obj-$(CONFIG_COMMON_CLK)     += clk-composite.o
>>>>
>>>>    # SoCs specific
>>>>    obj-$(CONFIG_ARCH_BCM2835)   += clk-bcm2835.o
>>>>
>>>> diff --git a/drivers/clk/clk-composite.c
>>>> b/drivers/clk/clk-composite.c
>>>> new file mode 100644
>>>> index 0000000..5a6587f
>>>> --- /dev/null
>>>> +++ b/drivers/clk/clk-composite.c
>>>> @@ -0,0 +1,208 @@
>>>> +/*
>>>> + * Copyright (c) 2013 NVIDIA CORPORATION.  All rights reserved.
>>>> + *
>>>> + * This program is free software; you can redistribute it and/or
>>>> modify it + * under the terms and conditions of the GNU General
>>>> Public License, + * version 2, as published by the Free Software
>>>> Foundation. + *
>>>> + * This program is distributed in the hope it will be useful, but
>>>> WITHOUT + * ANY WARRANTY; without even the implied warranty of
>>>> MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>>>> General Public License for + * more details.
>>>> + *
>>>> + * You should have received a copy of the GNU General Public License
>>>> + * along with this program.  If not, see
>>>> <http://www.gnu.org/licenses/>. + */
>>>> +
>>>> +#include <linux/clk.h>
>>>> +#include <linux/clk-provider.h>
>>>> +#include <linux/err.h>
>>>> +#include <linux/slab.h>
>>>> +
>>>> +#define to_clk_composite(_hw) container_of(_hw, struct
>>>> clk_composite,
>>>> hw) +
>>>> +static u8 clk_composite_get_parent(struct clk_hw *hw)
>>>> +{
>>>> +     struct clk_composite *composite = to_clk_composite(hw);
>>>> +     const struct clk_ops *mux_ops = composite->mux_ops;
>>>> +     struct clk_hw *mux_hw = composite->mux_hw;
>>>> +
>>>> +     mux_hw->clk = hw->clk;
>>> Why is this needed? Looks like this filed is already being initialized
>>> in clk_register_composite.
>> Some ops will get called during clk_init where this clk is not populated
>> hence doing here. I have done it for all ops to make sure that any
>> future change in clock framework don't break this clock.
>> Now, why duplicate it in clk_register_composite? It is possible that
>> none of these ops get called in clk_init.
>> For example, recalc_rate is called during init and this ops is supported
>> by div clock type, but what if div clock is not added.
>>
>> I hope this explains the need.
>>
> Sorry, I don't understand your explanation.
>
> I have asked why mux_hw->clk field has to be reinitialized in all the ops.
>
> In other words, is it even possible that this clk pointer changes since
> calling clk_register from clk_register_composite and if yes, why?

Tomasz,

calling sequence is as

clk_register(struct clk_hw *hw)
     clk_init(struct clk_hw *hw)
         .
         .
         hw->clk = clk;
         clk->ops.recalc_rate(hw) => clk_composite_recalc_rate(hw) => 
composite->div_ops.recalc_rate(div_hw) => clk_divider_recalc_rate(hw)

Now if clk_divider_recalc_rate tries to access clk from hw then it will 
get NULL since this is not assigned yet and that is what I am doing in 
clk_composite_recalc_rate.

I am doing it in all ops because I can not assume which one will get 
called first and always. If in future something changes the calling 
sequence in ccf framework then it will break this clock.

> Best regards,
> --
> Tomasz Figa
> Samsung Poland R&D Center
> SW Solution Development, Linux Platform
>
>>>> +
>>>> +     return mux_ops->get_parent(mux_hw);
>>>> +}
>>>> +
>>>> +static int clk_composite_set_parent(struct clk_hw *hw, u8 index)
>>>> +{
>>>> +     struct clk_composite *composite = to_clk_composite(hw);
>>>> +     const struct clk_ops *mux_ops = composite->mux_ops;
>>>> +     struct clk_hw *mux_hw = composite->mux_hw;
>>>> +
>>>> +     mux_hw->clk = hw->clk;
>>> Ditto.
>>>
>>>> +
>>>> +     return mux_ops->set_parent(mux_hw, index);
>>>> +}
>>>> +
>>>> +static unsigned long clk_composite_recalc_rate(struct clk_hw *hw,
>>>> +                                         unsigned long parent_rate)
>>>> +{
>>>> +     struct clk_composite *composite = to_clk_composite(hw);
>>>> +     const struct clk_ops *div_ops = composite->div_ops;
>>>> +     struct clk_hw *div_hw = composite->div_hw;
>>>> +
>>>> +     div_hw->clk = hw->clk;
>>> Ditto.
>>>
>>>> +
>>>> +     return div_ops->recalc_rate(div_hw, parent_rate);
>>>> +}
>>>> +
>>>> +static long clk_composite_round_rate(struct clk_hw *hw, unsigned
>>>> long
>>>> rate, +                                 unsigned long *prate)
>>>> +{
>>>> +     struct clk_composite *composite = to_clk_composite(hw);
>>>> +     const struct clk_ops *div_ops = composite->div_ops;
>>>> +     struct clk_hw *div_hw = composite->div_hw;
>>>> +
>>>> +     div_hw->clk = hw->clk;
>>> Ditto.
>>>
>>>> +
>>>> +     return div_ops->round_rate(div_hw, rate, prate);
>>>> +}
>>>> +
>>>> +static int clk_composite_set_rate(struct clk_hw *hw, unsigned long
>>>> rate, +                              unsigned long parent_rate)
>>>> +{
>>>> +     struct clk_composite *composite = to_clk_composite(hw);
>>>> +     const struct clk_ops *div_ops = composite->div_ops;
>>>> +     struct clk_hw *div_hw = composite->div_hw;
>>>> +
>>>> +     div_hw->clk = hw->clk;
>>> Ditto.
>>>
>>>> +
>>>> +     return div_ops->set_rate(div_hw, rate, parent_rate);
>>>> +}
>>>> +
>>>> +static int clk_composite_is_enabled(struct clk_hw *hw)
>>>> +{
>>>> +     struct clk_composite *composite = to_clk_composite(hw);
>>>> +     const struct clk_ops *gate_ops = composite->gate_ops;
>>>> +     struct clk_hw *gate_hw = composite->gate_hw;
>>>> +
>>>> +     gate_hw->clk = hw->clk;
>>> Ditto.
>>>
>>>> +
>>>> +     return gate_ops->is_enabled(gate_hw);
>>>> +}
>>>> +
>>>> +static int clk_composite_enable(struct clk_hw *hw)
>>>> +{
>>>> +     struct clk_composite *composite = to_clk_composite(hw);
>>>> +     const struct clk_ops *gate_ops = composite->gate_ops;
>>>> +     struct clk_hw *gate_hw = composite->gate_hw;
>>>> +
>>>> +     gate_hw->clk = hw->clk;
>>> Ditto.
>>>
>>>> +
>>>> +     return gate_ops->enable(gate_hw);
>>>> +}
>>>> +
>>>> +static void clk_composite_disable(struct clk_hw *hw)
>>>> +{
>>>> +     struct clk_composite *composite = to_clk_composite(hw);
>>>> +     const struct clk_ops *gate_ops = composite->gate_ops;
>>>> +     struct clk_hw *gate_hw = composite->gate_hw;
>>>> +
>>>> +     gate_hw->clk = hw->clk;
>>> Ditto.
>>>
>>>> +
>>>> +     gate_ops->disable(gate_hw);
>>>> +}
>>>> +
>>>> +struct clk *clk_register_composite(struct device *dev, const char
>>>> *name, +                      const char **parent_names, int
>>>> num_parents, +                     struct clk_hw *mux_hw, const
>>>> struct clk_ops *mux_ops, +                     struct clk_hw
>>>> *div_hw, const struct clk_ops *div_ops, +                     struct
>>>> clk_hw *gate_hw, const struct clk_ops *gate_ops, +
>>>>    unsigned long flags)
>>>> +{
>>>> +     struct clk *clk;
>>>> +     struct clk_init_data init;
>>>> +     struct clk_composite *composite;
>>>> +     struct clk_ops *clk_composite_ops;
>>>> +
>>>> +     composite = kzalloc(sizeof(*composite), GFP_KERNEL);
>>>> +     if (!composite) {
>>>> +             pr_err("%s: could not allocate composite clk\n",
>>>> __func__); +             return ERR_PTR(-ENOMEM);
>>>> +     }
>>>> +
>>>> +     init.name = name;
>>>> +     init.flags = flags | CLK_IS_BASIC;
>>>> +     init.parent_names = parent_names;
>>>> +     init.num_parents = num_parents;
>>>> +
>>>> +     /* allocate the clock ops */
>>>> +     clk_composite_ops = kzalloc(sizeof(*clk_composite_ops),
>>>> GFP_KERNEL); +     if (!clk_composite_ops) {
>>>> +             pr_err("%s: could not allocate clk ops\n", __func__);
>>>> +             kfree(composite);
>>>> +             return ERR_PTR(-ENOMEM);
>>>> +     }
>>> Maybe it would be better to embed this struct clk_ops inside struct
>>> clk_composite? This would allow to get rid of this allocation.
>>>
>>>> +
>>>> +     if (mux_hw && mux_ops) {
>>>> +             if (!mux_ops->get_parent || !mux_ops->set_parent) {
>>>> +                     clk = ERR_PTR(-EINVAL);
>>>> +                     goto err;
>>>> +             }
>>>> +
>>>> +             composite->mux_hw = mux_hw;
>>>> +             composite->mux_ops = mux_ops;
>>>> +             clk_composite_ops->get_parent =
>>>> clk_composite_get_parent;
>>>> +             clk_composite_ops->set_parent =
>>>> clk_composite_set_parent;
>>>> +     }
>>>> +
>>>> +     if (div_hw && div_ops) {
>>>> +             if (!div_ops->recalc_rate || !div_ops->round_rate ||
>>>> +                 !div_ops->set_rate) {
>>>> +                     clk = ERR_PTR(-EINVAL);
>>>> +                     goto err;
>>>> +             }
>>>> +
>>>> +             composite->div_hw = div_hw;
>>>> +             composite->div_ops = div_ops;
>>>> +             clk_composite_ops->recalc_rate =
>>>> clk_composite_recalc_rate; +
>>>> clk_composite_ops->round_rate = clk_composite_round_rate; +
>>>>     clk_composite_ops->set_rate = clk_composite_set_rate; +     }
>>>> +
>>>> +     if (gate_hw && gate_ops) {
>>>> +             if (!gate_ops->is_enabled || !gate_ops->enable ||
>>>> +                 !gate_ops->disable) {
>>>> +                     clk = ERR_PTR(-EINVAL);
>>>> +                     goto err;
>>>> +             }
>>>> +
>>>> +             composite->gate_hw = gate_hw;
>>>> +             composite->gate_ops = gate_ops;
>>>> +             clk_composite_ops->is_enabled =
>>>> clk_composite_is_enabled;
>>>> +             clk_composite_ops->enable = clk_composite_enable;
>>>> +             clk_composite_ops->disable = clk_composite_disable;
>>>> +     }
>>>> +
>>>> +     init.ops = clk_composite_ops;
>>>> +     composite->hw.init = &init;
>>>> +
>>>> +     clk = clk_register(dev, &composite->hw);
>>>> +     if (IS_ERR(clk))
>>>> +             goto err;
>>>> +
>>>> +     if (composite->mux_hw)
>>>> +             composite->mux_hw->clk = clk;
>>>> +
>>>> +     if (composite->div_hw)
>>>> +             composite->div_hw->clk = clk;
>>>> +
>>>> +     if (composite->gate_hw)
>>>> +             composite->gate_hw->clk = clk;
>>>> +
>>>> +     return clk;
>>>> +
>>>> +err:
>>>> +     kfree(clk_composite_ops);
>>>> +     kfree(composite);
>>>> +     return clk;
>>>> +}
>>>> diff --git a/include/linux/clk-provider.h
>>>> b/include/linux/clk-provider.h index 7f197d7..f1a36aa 100644
>>>> --- a/include/linux/clk-provider.h
>>>> +++ b/include/linux/clk-provider.h
>>>> @@ -325,6 +325,36 @@ struct clk *clk_register_fixed_factor(struct
>>>> device *dev, const char *name, const char *parent_name, unsigned
>>>> long flags,>>
>>>>                 unsigned int mult, unsigned int div);
>>>>
>>>> +/***
>>>> + * struct clk_composite - aggregate clock of mux, divider and gate
>>>> clocks + *
>>>> + * @hw:              handle between common and hardware-specific
>>>> interfaces + * @mux_hw:  handle between composite and
>>>> hardware-specifix mux clock + * @div_hw:  handle between composite
>>>> and hardware-specifix divider clock + * @gate_hw:   handle between
>>>> composite and hardware-specifix gate clock + * @mux_ops:   clock ops
>>>> for mux
>>>> + * @div_ops: clock ops for divider
>>>> + * @gate_ops:        clock ops for gate
>>>> + */
>>>> +struct clk_composite {
>>>> +     struct clk_hw   hw;
>>> As I suggested above:
>>>           struct clk_ops  ops;
>>>> +
>>>> +     struct clk_hw   *mux_hw;
>>>> +     struct clk_hw   *div_hw;
>>>> +     struct clk_hw   *gate_hw;
>>>> +
>>>> +     const struct clk_ops    *mux_ops;
>>>> +     const struct clk_ops    *div_ops;
>>>> +     const struct clk_ops    *gate_ops;
>>>> +};
>>>> +
>>>> +struct clk *clk_register_composite(struct device *dev, const char
>>>> *name, +              const char **parent_names, int num_parents,
>>>> +             struct clk_hw *mux_hw, const struct clk_ops *mux_ops,
>>>> +             struct clk_hw *div_hw, const struct clk_ops *div_ops,
>>>> +             struct clk_hw *gate_hw, const struct clk_ops *gate_ops,
>>>> +             unsigned long flags);
>>>> +
>>>>
>>>>    /**
>>>>
>>>>     * clk_register - allocate a new clock, register it and return an
>>>>
>>>> opaque cookie * @dev: device that is registering this clock
>>> Best regards,
>>> --
>>> Tomasz Figa
>>> Samsung Poland R&D Center
>>> SW Solution Development, Linux Platform
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