linux-kernel - Re: [PATCH v3 4/7] leds: rgb: leds-qcom-lpg: Add support for PPG through single SDAM

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Date:   Tue, 15 Aug 2023 17:09:58 -0700
From:   Anjelique Melendez <quic_amelende@...cinc.com>
To:     Bjorn Andersson <andersson@...nel.org>
CC:     <pavel@....cz>, <lee@...nel.org>, <thierry.reding@...il.com>,
        <robh+dt@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <conor+dt@...nel.org>, <agross@...nel.org>,
        <luca.weiss@...rphone.com>, <konrad.dybcio@...aro.org>,
        <u.kleine-koenig@...gutronix.de>, <quic_subbaram@...cinc.com>,
        <linux-leds@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-pwm@...r.kernel.org>
Subject: Re: [PATCH v3 4/7] leds: rgb: leds-qcom-lpg: Add support for PPG
 through single SDAM



On 8/15/2023 8:38 AM, Bjorn Andersson wrote:
> On Mon, Aug 14, 2023 at 04:59:15PM -0700, Anjelique Melendez wrote:

[...]>> @@ -65,7 +83,12 @@ struct lpg_data;
>>   * @lut_base:	base address of the LUT block (optional)
>>   * @lut_size:	number of entries in the LUT block
>>   * @lut_bitmap:	allocation bitmap for LUT entries
>> - * @triled_base: base address of the TRILED block (optional)
>> + * @pbs_dev:	PBS device
>> + * @lpg_chan_nvmem:	LPG nvmem peripheral device
>> + * @pbs_en_bitmap:	bitmap for tracking PBS triggers
>> + * @lut_sdam_base:	offset where LUT pattern begins in nvmem
>> + * @ppg_en:	Flag indicating whether PPG is enabled/used
> 
> Looking at its usage, it doesn't feel so much "is PPG enabled" as "does
> this instance use PPG", it's not a thing that can be enabled/disabled in
> runtime.
> 
> So "has_ppg" seems like a better name, or perhaps even "use_sdam" and
> avoid "PPG" completely and make it clearer to the average reader?
Sure, can update to be "use_sdam"


[...]
>> +static void lpg_sdam_configure_triggers(struct lpg_channel *chan)
>> +{
>> +	if (!chan->lpg->ppg_en)
>> +		return;
>> +
>> +	if (chan->enabled && chan->pattern_set) {
>> +		lpg_sdam_write(chan->lpg, SDAM_LUT_EN_OFFSET + chan->sdam_offset, 1);
>> +		lpg_set_pbs_trigger(chan);
>> +		chan->pattern_set = false;
> 
> Forgive me if I'm confused, but doesn't this mean that if I configure a
> pattern and then set the brightness twice the pattern will be disabled
> again?
Yes, you are correct. With current code we continuously disable pattern.
I took a look at the code again and found that it makes more sense to
disable pattern in clear_pattern().


[...]
>> @@ -1363,7 +1618,9 @@ static int lpg_probe(struct platform_device *pdev)
>>  	for (i = 0; i < lpg->num_channels; i++)
>>  		lpg_apply_dtest(&lpg->channels[i]);
>>  
>> -	return lpg_add_pwm(lpg);
>> +	ret = lpg_add_pwm(lpg);
>> +
>> +	return ret;
> 
> I'm failing to see the usefulness of this change.
Sorry, looks like this was never reverted from an old change when I was debugging.
Will revert back to original for next version. 

Thanks,
Anjelique