linux-kernel - Re: [PATCH] clk: ti: divider: Add the table parsing to get the best divider value

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Date:   Wed, 25 Jan 2017 15:05:08 +0200
From:   Tero Kristo <t-kristo@...com>
To:     Keerthy <j-keerthy@...com>
CC:     <mturquette@...libre.com>, <sboyd@...eaurora.org>,
        <linux-omap@...r.kernel.org>, <linux-clk@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] clk: ti: divider: Add the table parsing to get the best
 divider value

On 25/01/17 12:37, Keerthy wrote:
>
>
> On Friday 02 December 2016 02:35 PM, Keerthy wrote:
>> Currently the divider selection logic blindly divides the parent_rate
>> by the clk rate and gives the divider value for the divider clocks
>> which do not have the CLK_SET_RATE_PARENT flag set. Add the clk divider
>> table parsing to get the closest divider available in the table
>> provided via Device tree.
>>
>> The code is pretty much taken from: drivers/clk/clk-divider.c.
>> and used here to fix up the best divider selection logic.
>
> A gentle ping on this patch. This applies cleanly on the next branch as
> on today. Let me know if this needs to be rebased.
>
> - Keerthy
>
>>
>> Signed-off-by: Keerthy <j-keerthy@...com>
>> Reported-by: Richard Woodruff <r-woodruff2@...com>

Acked-by: Tero Kristo <t-kristo@...com>

Stephen / Michael, can you pick this up?

-Tero

>> ---
>>  drivers/clk/ti/divider.c | 31 ++++++++++++++++++++++++++++++-
>>  1 file changed, 30 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/clk/ti/divider.c b/drivers/clk/ti/divider.c
>> index b4e5de1..6bb8778 100644
>> --- a/drivers/clk/ti/divider.c
>> +++ b/drivers/clk/ti/divider.c
>> @@ -140,6 +140,35 @@ static bool _is_valid_div(struct clk_divider
>> *divider, unsigned int div)
>>      return true;
>>  }
>>
>> +static int _div_round_up(const struct clk_div_table *table,
>> +             unsigned long parent_rate, unsigned long rate)
>> +{
>> +    const struct clk_div_table *clkt;
>> +    int up = INT_MAX;
>> +    int div = DIV_ROUND_UP_ULL((u64)parent_rate, rate);
>> +
>> +    for (clkt = table; clkt->div; clkt++) {
>> +        if (clkt->div == div)
>> +            return clkt->div;
>> +        else if (clkt->div < div)
>> +            continue;
>> +
>> +        if ((clkt->div - div) < (up - div))
>> +            up = clkt->div;
>> +    }
>> +
>> +    return up;
>> +}
>> +
>> +static int _div_round(const struct clk_div_table *table,
>> +              unsigned long parent_rate, unsigned long rate)
>> +{
>> +    if (!table)
>> +        return DIV_ROUND_UP(parent_rate, rate);
>> +
>> +    return _div_round_up(table, parent_rate, rate);
>> +}
>> +
>>  static int ti_clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
>>                    unsigned long *best_parent_rate)
>>  {
>> @@ -155,7 +184,7 @@ static int ti_clk_divider_bestdiv(struct clk_hw
>> *hw, unsigned long rate,
>>
>>      if (!(clk_hw_get_flags(hw) & CLK_SET_RATE_PARENT)) {
>>          parent_rate = *best_parent_rate;
>> -        bestdiv = DIV_ROUND_UP(parent_rate, rate);
>> +        bestdiv = _div_round(divider->table, parent_rate, rate);
>>          bestdiv = bestdiv == 0 ? 1 : bestdiv;
>>          bestdiv = bestdiv > maxdiv ? maxdiv : bestdiv;
>>          return bestdiv;
>>