Message-ID: <4FBB19E6.2040403@ti.com>
Date:	Tue, 22 May 2012 10:15:26 +0530
From:	Rajendra Nayak <rnayak@...com>
To:	Ben Dooks <ben.dooks@...ethink.co.uk>
CC:	mturquette@...com, mturquette@...aro.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/2] clk: Add support for rate table based dividers

Hi Ben,

On Monday 21 May 2012 03:17 PM, Ben Dooks wrote:
> On 17/05/12 11:22, Rajendra Nayak wrote:
>> Some divider clks do not have any obvious relationship
>> between the divider and the value programmed in the
>> register. For instance, say a value of 1 could signify divide
>> by 6 and a value of 2 could signify divide by 4 etc.
>> Also there are dividers where not all values possible
>> based on the bitfield width are valid. For instance
>> a 3 bit wide bitfield can be used to program a value
>> from 0 to 7. However its possible that only 0 to 4
>> are valid values.
>>
>> All these cases need the platform code to pass a simple
>> table of divider/value tuple, so the framework knows
>> the exact value to be written based on the divider
>> calculation and can also do better error checking.
>>
>> This patch adds support for such rate table based
>> dividers.
>
> I was considering the idea that you simply pass a
> pointer to a set of routines and a data pointer to
> the clk-divider code so that any new cases don't
> require changing the drivers/clk/clk-divider.c

I don;t know if I understand your comment completely.
Are you suggesting the get min/max etc be function pointers
passed by platform code (and implemented in platform code?)
so clk-divider does not need an update every time a new divider
type is added?
The idea of extending clk-divider was so its useful for more
than just OMAP, so the code in clk-divider can be reused across
multiple platforms. Did I understand your comment right?

regards,
Rajendra

>
> This would make the get max / min / special just
> a function call through a struct.
>
>> Signed-off-by: Rajendra Nayak<rnayak@...com>
>> ---
>> drivers/clk/clk-divider.c | 67 ++++++++++++++++++++++++++++++++++++++++--
>> include/linux/clk-private.h | 3 +-
>> include/linux/clk-provider.h | 10 +++++-
>> 3 files changed, 75 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
>> index e548c43..e4911ee 100644
>> --- a/drivers/clk/clk-divider.c
>> +++ b/drivers/clk/clk-divider.c
>> @@ -32,30 +32,69 @@
>> #define div_mask(d) ((1<< (d->width)) - 1)
>> #define is_power_of_two(i) !(i& ~i)
>>
>> +static unsigned int _get_table_maxdiv(const struct clk_div_table *table)
>> +{
>> + unsigned int maxdiv;
>> + const struct clk_div_table *clkt;
>> +
>> + for (clkt = table; clkt->div; clkt++)
>> + if (clkt->div> maxdiv)
>> + maxdiv = clkt->div;
>> + return maxdiv;
>> +}
>> +
>> static unsigned int _get_maxdiv(struct clk_divider *divider)
>> {
>> if (divider->flags& CLK_DIVIDER_ONE_BASED)
>> return div_mask(divider);
>> if (divider->flags& CLK_DIVIDER_POWER_OF_TWO)
>> return 1<< div_mask(divider);
>> + if (divider->table)
>> + return _get_table_maxdiv(divider->table);
>> return div_mask(divider) + 1;
>> }
>>
>> +static unsigned int _get_table_div(const struct clk_div_table *table,
>> + unsigned int val)
>> +{
>> + const struct clk_div_table *clkt;
>> +
>> + for (clkt = table; clkt->div; clkt++)
>> + if (clkt->val == val)
>> + return clkt->div;
>> + return 0;
>> +}
>> +
>> static unsigned int _get_div(struct clk_divider *divider, unsigned int
>> val)
>> {
>> if (divider->flags& CLK_DIVIDER_ONE_BASED)
>> return val;
>> if (divider->flags& CLK_DIVIDER_POWER_OF_TWO)
>> return 1<< val;
>> + if (divider->table)
>> + return _get_table_div(divider->table, val);
>> return val + 1;
>> }
>>
>> +static unsigned int _get_table_val(const struct clk_div_table *table,
>> + unsigned int div)
>> +{
>> + const struct clk_div_table *clkt;
>> +
>> + for (clkt = table; clkt->div; clkt++)
>> + if (clkt->div == div)
>> + return clkt->val;
>> + return 0;
>> +}
>> +
>> static unsigned int _get_val(struct clk_divider *divider, u8 div)
>> {
>> if (divider->flags& CLK_DIVIDER_ONE_BASED)
>> return div;
>> if (divider->flags& CLK_DIVIDER_POWER_OF_TWO)
>> return __ffs(div);
>> + if (divider->table)
>> + return _get_table_val(divider->table, div);
>> return div - 1;
>> }
>>
>> @@ -84,6 +123,26 @@ static unsigned long
>> clk_divider_recalc_rate(struct clk_hw *hw,
>> */
>> #define MULT_ROUND_UP(r, m) ((r) * (m) + (m) - 1)
>>
>> +static bool _is_valid_table_div(const struct clk_div_table *table,
>> + unsigned int div)
>> +{
>> + const struct clk_div_table *clkt;
>> +
>> + for (clkt = table; clkt->div; clkt++)
>> + if (clkt->div == div)
>> + return true;
>> + return false;
>> +}
>> +
>> +static bool _is_valid_div(struct clk_divider *divider, unsigned int div)
>> +{
>> + if (divider->flags& CLK_DIVIDER_POWER_OF_TWO)
>> + return is_power_of_two(div);
>> + if (divider->table)
>> + return _is_valid_table_div(divider->table, div);
>> + return true;
>> +}
>> +
>> static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
>> unsigned long *best_parent_rate)
>> {
>> @@ -111,8 +170,7 @@ static int clk_divider_bestdiv(struct clk_hw *hw,
>> unsigned long rate,
>> maxdiv = min(ULONG_MAX / rate, maxdiv);
>>
>> for (i = 1; i<= maxdiv; i++) {
>> - if ((divider->flags& CLK_DIVIDER_POWER_OF_TWO)
>> - && (!is_power_of_two(i)))
>> + if (!_is_valid_div(divider, i))
>> continue;
>> parent_rate = __clk_round_rate(__clk_get_parent(hw->clk),
>> MULT_ROUND_UP(rate, i));
>> @@ -186,12 +244,14 @@ EXPORT_SYMBOL_GPL(clk_divider_ops);
>> * @shift: number of bits to shift the bitfield
>> * @width: width of the bitfield
>> * @clk_divider_flags: divider-specific flags for this clock
>> + * @table: array of divider/value pairs ending with a div set to 0
>> * @lock: shared register lock for this clock
>> */
>> struct clk *clk_register_divider(struct device *dev, const char *name,
>> const char *parent_name, unsigned long flags,
>> void __iomem *reg, u8 shift, u8 width,
>> - u8 clk_divider_flags, spinlock_t *lock)
>> + u8 clk_divider_flags, const struct clk_div_table *table,
>> + spinlock_t *lock)
>> {
>> struct clk_divider *div;
>> struct clk *clk;
>> @@ -217,6 +277,7 @@ struct clk *clk_register_divider(struct device
>> *dev, const char *name,
>> div->flags = clk_divider_flags;
>> div->lock = lock;
>> div->hw.init =&init;
>> + div->table = table;
>>
>> /* register the clock */
>> clk = clk_register(dev,&div->hw);
>> diff --git a/include/linux/clk-private.h b/include/linux/clk-private.h
>> index eb3f84b..2479239 100644
>> --- a/include/linux/clk-private.h
>> +++ b/include/linux/clk-private.h
>> @@ -105,7 +105,7 @@ struct clk {
>>
>> #define DEFINE_CLK_DIVIDER(_name, _parent_name, _parent_ptr, \
>> _flags, _reg, _shift, _width, \
>> - _divider_flags, _lock) \
>> + _divider_flags, _table, _lock) \
>> static struct clk _name; \
>> static const char *_name##_parent_names[] = { \
>> _parent_name, \
>> @@ -121,6 +121,7 @@ struct clk {
>> .shift = _shift, \
>> .width = _width, \
>> .flags = _divider_flags, \
>> + .table = _table, \
>> .lock = _lock, \
>> }; \
>> DEFINE_CLK(_name, clk_divider_ops, _flags, \
>> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
>> index 4a0b483..22bc067 100644
>> --- a/include/linux/clk-provider.h
>> +++ b/include/linux/clk-provider.h
>> @@ -203,6 +203,11 @@ struct clk *clk_register_gate(struct device *dev,
>> const char *name,
>> void __iomem *reg, u8 bit_idx,
>> u8 clk_gate_flags, spinlock_t *lock);
>>
>> +struct clk_div_table {
>> + unsigned int val;
>> + unsigned int div;
>> +};
>> +
>> /**
>> * struct clk_divider - adjustable divider clock
>> *
>> @@ -210,6 +215,7 @@ struct clk *clk_register_gate(struct device *dev,
>> const char *name,
>> * @reg: register containing the divider
>> * @shift: shift to the divider bit field
>> * @width: width of the divider bit field
>> + * @table: array of value/divider pairs, last entry should have div = 0
>> * @lock: register lock
>> *
>> * Clock with an adjustable divider affecting its output frequency.
>> Implements
>> @@ -229,6 +235,7 @@ struct clk_divider {
>> u8 shift;
>> u8 width;
>> u8 flags;
>> + const struct clk_div_table *table;
>> spinlock_t *lock;
>> };
>>
>> @@ -239,7 +246,8 @@ extern const struct clk_ops clk_divider_ops;
>> struct clk *clk_register_divider(struct device *dev, const char *name,
>> const char *parent_name, unsigned long flags,
>> void __iomem *reg, u8 shift, u8 width,
>> - u8 clk_divider_flags, spinlock_t *lock);
>> + u8 clk_divider_flags, const struct clk_div_table *table,
>> + spinlock_t *lock);
>>
>> /**
>> * struct clk_mux - multiplexer clock
>
>

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