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Date: Mon, 21 May 2012 10:47:41 +0100
From: Ben Dooks <ben.dooks@...ethink.co.uk>
To: Rajendra Nayak <rnayak@...com>
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
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
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
--
Ben Dooks http://www.codethink.co.uk/
Senior Engineer Codethink - Providing Genius
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