On 7.09.2023 21:55, Anjelique Melendez wrote: > > > On 8/30/2023 11:34 AM, Konrad Dybcio wrote: >> On 30.08.2023 20:05, Anjelique Melendez wrote: >>> In some PMICs like pmi632, the pattern look up table (LUT) and LPG >>> configuration can be stored in a single SDAM module instead of LUT >>> peripheral. This feature is called PPG. PPG uses Qualcomm Programmable >>> Boot Sequencer (PBS) inorder to trigger pattern sequences for PMICs. >> I still fail to understand what benefit this brings. >> >> Is this a "can be used", or "should be used", or maybe "must be used"? >> >> Are there any distinct advantages to using one over the other? >> I see some limitations in the code below, but that's not being made >> obvious. >> >> This all should be in the commit message, the current one includes >> a lot of cryptic names that mean nothing to most people. >> >> [...] > This is a must be used if you would like to trigger patterns. Will update commit message to try and > make that more clear for next patch. So essentially without this patchset, PM8350C and PMI632 are not capable of producing LED patterns. Is that correct? [...] >>> @@ -860,14 +1043,21 @@ static int lpg_pattern_set(struct lpg_led *led, struct led_pattern *led_pattern, >>> * Validate that all delta_t in the pattern are the same, with the >>> * exception of the middle element in case of ping_pong. >>> */ >>> - delta_t = pattern[1].delta_t; >>> - for (i = 2; i < len; i++) { >>> + if (lpg->lpg_chan_nvmem) { >>> + i = 1; >>> + delta_t = pattern[0].delta_t; >>> + } else { >>> + i = 2; >>> + delta_t = pattern[1].delta_t; >>> + } >> Why? >> >> What's the rationale behind this change? > Patterns are required to have the same duration for each step of the pattern. Devices with LUT peripherals support low/high > pause which is when the first/last entry of the pattern can have a longer duration. This loop checks that the all of the > pattern durations are the same with the exception of the first and last entry for low/hi pause. That's the explanation I was looking for! :) Things like these that are only known to inside folks should definitely be stated either as a comment, or inside the commit message. Since you're changing the code flow in a noticeable manner, this could probably be a good fit for a comment. > > This change was made because devices that use single SDAM do not support low/high pause, so we must check every > single pattern duration. Instead of changing the loop arguments with an if statement I was thinking we could either: > > a. keep the original loop arguments and when loop exits we can check first element for single SDAM devices > > delta_t = pattern[1].delta_t; > for (i = 2; i < len; i++) { > if (pattern[i].delta_t != delta_t) { > + if (i != actual_len - 1 || lpg->lpg_chan_nvmem) > goto out_free_pattern; > } > } > > + if (lpg->lpg_chan_nvmem) { > + if (delta_t != pattern[0].delta_t) > + goto out_free_pattern > + } We assign hi/lo_pause a couple lines below. Moving these assignments a bit higher up could let us make this clearer: /* LPGs using SDAM for patterns require equal duration of all steps */ if ((delta_t != lo_pause) && lpg->lpg_chan_nvmem) goto out_free_pattern; Though I think that (in a separate patch, or perhaps series), it would be worth redoing the code such that hi/lo_pause expresses the deviation from the duration of the rest instead of the duration itself. Then we could just: if ((lo_pause || hi_pause)) && lpg->lpg_chan_nvmem) goto out_free_pattern; But that's just a suggestion from somebody that didn't work on this code. Also, I think that using lpg_chan_nvmem interchangeably with SDAM is a bit confusing. Do we expect NVMEMs/SRAMs that aren't SDAM to make an appearence here? > > b. Change the loop argument to start with i=0 and for LUT device we could just skip checking first and last element duration > ** We would end up checking if pattern[1].delta_t == pattern[1].delta_t inside the loop when i == 1 > > delta_t = pattern[1].delta_t; > + for (i = 0; i < len; i++) { > if (pattern[i].delta_t != delta_t) { > + if (lpg->lut_base && (i == 0 || i == actual_len - 1) > + continue; > + else > + goto out_free_pattern; Meh, too many magic literals for my liking Konrad