Re: [PATCH v6 2/3] clk: qcom: clk-rcg2: add support for rcg2 freq multi ops

Devi Priya
2023-11-21T06:31:38Z

On 11/20/2023 11:44 PM, Christian Marangi wrote:
> On Mon, Nov 20, 2023 at 03:51:50PM +0530, Devi Priya wrote:
>>
>>
>> On 9/16/2023 7:30 PM, Christian Marangi wrote:
>>> Some RCG frequency can be reached by multiple configuration.
>>>
>>> Add clk_rcg2_fm_ops ops to support these special RCG configurations.
>>>
>>> These alternative ops will select the frequency using a CEIL policy.
>>>
>>> When the correct frequency is found, the correct config is selected by
>>> calculating the final rate (by checking the defined parent and values
>>> in the config that is being checked) and deciding based on the one that
>>> is less different than the requested one.
>>>
>>> These check are skipped if there is just on config for the requested
>>> freq.
>>>
>>> qcom_find_freq_multi is added to search the freq with the new struct
>>> freq_multi_tbl.
>>> __clk_rcg2_select_conf is used to select the correct conf by simulating
>>> the final clock.
>>> If a conf can't be found due to parent not reachable, a WARN is printed
>>> and -EINVAL is returned.
>>>
>>> Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
>>> ---
>>> drivers/clk/qcom/clk-rcg.h | 1 +
>>> drivers/clk/qcom/clk-rcg2.c | 167 ++++++++++++++++++++++++++++++++++++
>>> drivers/clk/qcom/common.c | 18 ++++
>>> drivers/clk/qcom/common.h | 2 +
>>> 4 files changed, 188 insertions(+)
>>>
>>> diff --git a/drivers/clk/qcom/clk-rcg.h b/drivers/clk/qcom/clk-rcg.h
>>> index c81458db6ce4..dc9a77965e68 100644
>>> --- a/drivers/clk/qcom/clk-rcg.h
>>> +++ b/drivers/clk/qcom/clk-rcg.h
>>> @@ -190,6 +190,7 @@ struct clk_rcg2_gfx3d {
>>> extern const struct clk_ops clk_rcg2_ops;
>>> extern const struct clk_ops clk_rcg2_floor_ops;
>>> +extern const struct clk_ops clk_rcg2_fm_ops;
>>> extern const struct clk_ops clk_rcg2_mux_closest_ops;
>>> extern const struct clk_ops clk_edp_pixel_ops;
>>> extern const struct clk_ops clk_byte_ops;
>>> diff --git a/drivers/clk/qcom/clk-rcg2.c b/drivers/clk/qcom/clk-rcg2.c
>>> index e22baf3a7112..617e7ff0f6a3 100644
>>> --- a/drivers/clk/qcom/clk-rcg2.c
>>> +++ b/drivers/clk/qcom/clk-rcg2.c
>>> @@ -266,6 +266,116 @@ static int _freq_tbl_determine_rate(struct clk_hw *hw, const struct freq_tbl *f,
>>> return 0;
>>> }
>>> +static const struct freq_conf *
>>> +__clk_rcg2_select_conf(struct clk_hw *hw, const struct freq_multi_tbl *f,
>>> + unsigned long req_rate)
>>> +{
>>> + unsigned long rate_diff, best_rate_diff = ULONG_MAX;
>>> + const struct freq_conf *conf, *best_conf;
>>> + struct clk_rcg2 *rcg = to_clk_rcg2(hw);
>>> + const char *name = clk_hw_get_name(hw);
>>> + unsigned long parent_rate, rate;
>>> + struct clk_hw *p;
>>> + int index, i;
>>> +
>>> + /* Init best_conf to the first conf */
>>> + best_conf = f->confs;
>>> +
>>> + /* Exit early if only one config is defined */
>>> + if (f->num_confs == 1)
>>> + goto exit;
>>> +
>>> + /* Search in each provided config the one that is near the wanted rate */
>>> + for (i = 0, conf = f->confs; i < f->num_confs; i++, conf++) {
>>> + index = qcom_find_src_index(hw, rcg->parent_map, conf->src);
>>> + if (index < 0)
>>> + continue;
>>> +
>>> + p = clk_hw_get_parent_by_index(hw, index);
>>> + if (!p)
>>> + continue;
>>> +
>>> + parent_rate = clk_hw_get_rate(p);
>>> + rate = calc_rate(parent_rate, conf->n, conf->m, conf->n, conf->pre_div);
>>> +
>>> + if (rate == req_rate) {
>>> + best_conf = conf;
>>> + goto exit;
>>> + }
>>> +
>>> + rate_diff = abs(req_rate - rate);
>>> + if (rate_diff < best_rate_diff) {
>>> + best_rate_diff = rate_diff;
>>> + best_conf = conf;
>>> + }
>>> + }
>>> +
>>> + /*
>>> + * Very unlikely. Warn if we couldn't find a correct config
>>> + * due to parent not found in every config.
>>> + */
>>> + if (unlikely(i == f->num_confs)) {
>>> + WARN(1, "%s: can't find a configuration for rate %lu.",
>>> + name, req_rate);
>>> + return ERR_PTR(-EINVAL);
>>> + }
>> Hi Christian,
>>
>> Thanks a lot for the patch!
>> We have incorporated these changes along with the corresponding clock driver
>> changes & tested it on IPQ9574 & IPQ5332 targets.
>>
>> When setting the clk rate for the nss port clocks, for the requested
>> frequency the correct config gets selected and the
>> clk rate is set properly.
>> We see the WARN getting printed for other frequencies (rate * i where
>> i=2 to maxdiv) that is requested by the clk_hw_round_rate function.
>>
>> Upon analysis, we see that the for loop in clk_divider_bestdiv iterates
>> until the maxdiv value and requests (rate*i) via the clk_hw_round_rate
>> API to find the bestdiv and best_parent_rate. For frequencies which are
>> multiples of the requested frequency (rate*i where i=2 to maxdiv), it
>> seems unlikely to see the WARN being printed.
>>
>> Can you please help us understand when the WARN is likely to be printed
>> & Looking forward to your suggestions on how this WARN could
>> be suppressed in the afore mentioned scenario!
>>
>
> Hi,
>
> thanks a lot for testing this. Maybe was a small oversight by me.
>
> I attached an alternative patch. Can you test it and tell me if the WARN
> is still printed? (the WARN must be printed only when the parent is not
> found, I don't think it's your case)
>
Hi Christian,

WARN does not get printed with the attached patchset.
Thanks much!

Regards,
Devi Priya