Re: [PATCH] clk: bcm/kona: implement determine_rate()

From: Alex Elder
Date: Fri May 23 2014 - 19:24:39 EST


On 05/23/2014 06:18 PM, Mike Turquette wrote:
> Quoting Alex Elder (2014-05-20 06:24:57)
>> Implement the clk->determine_rate method for Broadcom Kona peripheral
>> clocks. This allows a peripheral clock to be re-parented in order to
>> satisfy a rate change request. This takes the place of the previous
>> kona_peri_clk_round_rate() functionality, though that function remains
>> because it is used by the new one.
>>
>> The parent clock that allows the peripheral clock to produce a rate
>> closest to the one requested is the one selected, though the current
>> parent is used by default.
>>
>> Signed-off-by: Alex Elder <elder@xxxxxxxxxx>
>> ---
>> This patch is based on Mike Turquette's current "clk-next" branch.
>> 6ed8eb5 Merge tag 'clk-hisi-for-v3.16' of https://git.kern...
>>
>> It is available here:
>> http://git.linaro.org/landing-teams/working/broadcom/kernel.git
>> Branch review/bcm-determine-rate
>>
>> drivers/clk/bcm/clk-kona.c | 53 +++++++++++++++++++++++++++++++++++++++++++++-
>> 1 file changed, 52 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/clk/bcm/clk-kona.c b/drivers/clk/bcm/clk-kona.c
>> index d603c4e..1a4eccc 100644
>> --- a/drivers/clk/bcm/clk-kona.c
>> +++ b/drivers/clk/bcm/clk-kona.c
>> @@ -1031,6 +1031,57 @@ static long kona_peri_clk_round_rate(struct clk_hw *hw, unsigned long rate,
>> rate ? rate : 1, *parent_rate, NULL);
>> }
>>
>> +static long kona_peri_clk_determine_rate(struct clk_hw *hw, unsigned long rate,
>> + unsigned long *best_parent_rate, struct clk **best_parent)
>> +{
>> + struct kona_clk *bcm_clk = to_kona_clk(hw);
>> + struct clk *clk = hw->clk;
>> + struct clk *current_parent;
>> + unsigned long parent_rate;
>> + unsigned long best_delta;
>> + unsigned long best_rate;
>> + u32 parent_count;
>> + u32 which;
>> +
>> + /*
>> + * If there is no other parent to choose, use the current one.
>> + * Note: We don't honor (or use) CLK_SET_RATE_NO_REPARENT.
>> + */
>
> A WARN_ONCE is appropriate upon detection of CLK_SET_RATE_NO_REPARENT.
> It will certainly help someone that is debugging why that flag has no
> effect.

I'll add that.

> Otherwise the patch looks good to me.

Would you like me to send an updated patch as a pull request?

Thanks.

-Alex

> Regards,
> Mike
>
>> + parent_count = (u32)bcm_clk->init_data.num_parents;
>> + if (parent_count < 2)
>> + return kona_peri_clk_round_rate(hw, rate, best_parent_rate);
>> +
>> + /* Unless we can do better, stick with current parent */
>> + current_parent = clk_get_parent(clk);
>> + parent_rate = __clk_get_rate(current_parent);
>> + best_rate = kona_peri_clk_round_rate(hw, rate, &parent_rate);
>> + best_delta = abs(best_rate - rate);
>> +
>> + /* Check whether any other parent clock can produce a better result */
>> + for (which = 0; which < parent_count; which++) {
>> + struct clk *parent = clk_get_parent_by_index(clk, which);
>> + unsigned long delta;
>> + unsigned long other_rate;
>> +
>> + BUG_ON(!parent);
>> + if (parent == current_parent)
>> + continue;
>> +
>> + /* We don't support CLK_SET_RATE_PARENT */
>> + parent_rate = __clk_get_rate(parent);
>> + other_rate = kona_peri_clk_round_rate(hw, rate, &parent_rate);
>> + delta = abs(other_rate - rate);
>> + if (delta < best_delta) {
>> + best_delta = delta;
>> + best_rate = other_rate;
>> + *best_parent = parent;
>> + *best_parent_rate = parent_rate;
>> + }
>> + }
>> +
>> + return best_rate;
>> +}
>> +
>> static int kona_peri_clk_set_parent(struct clk_hw *hw, u8 index)
>> {
>> struct kona_clk *bcm_clk = to_kona_clk(hw);
>> @@ -1135,7 +1186,7 @@ struct clk_ops kona_peri_clk_ops = {
>> .disable = kona_peri_clk_disable,
>> .is_enabled = kona_peri_clk_is_enabled,
>> .recalc_rate = kona_peri_clk_recalc_rate,
>> - .round_rate = kona_peri_clk_round_rate,
>> + .determine_rate = kona_peri_clk_determine_rate,
>> .set_parent = kona_peri_clk_set_parent,
>> .get_parent = kona_peri_clk_get_parent,
>> .set_rate = kona_peri_clk_set_rate,
>> --
>> 1.9.1
>>

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