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I guess the result is somewhat >>> random: depending on load (power draw), silicon lottery (quality), >>> temperature, voltage supply, ... - one may or may not see crashes >>> caused by this. >> >> Yes, our glitch-free mux is designed to prevent glitches caused by >> excessively short high or low levels in the clock output. >> >> >>> Based on the previous discussion on this topic, my suggestion is to >>> split the original patch: >>> - one to add CLK_SET_RATE_GATE where needed (I think the meson8b.c >>> driver already has this where needed) to actually enable the >>> glitch-free mux behavior >>> - another one with the CLK_OPS_PARENT_ENABLE change (meson8b.c would >>> also need to be updated) to prevent the glitch-free mux from >>> temporarily outputting an electrical low signal. Jerome also asked to >>> document the behavior so we don't forget why we set this flag >>> >>> Both patches should get the proper "Fixes" tags. >>> I think it would also be great if you could include the waveform >>> example in at least the commit message as it helps understand the >>> problem. >>> >>> Let's also give Jerome some time to comment before you send patches. >> >> A V2 version was submitted later with changes based on your suggestions. >> Regarding the "Fixes" tag, Jerome had proposed some modifications. >> >> [PATCH v2 0/3] clk: Fix issues related to CLK_IGNORE_UNUSED failures and >> amlogic glitch free mux - Chuan Liu via B4 Relay >> >> > The comments I've provided on this still stands. > >> Adding CLK_OPS_PARENT_ENABLE causes the CLK_IGNORE_UNUSED configuration >> of it's parent clocks on the chain to become ineffective, so this patch >> depends on fixing that issue before it can proceed. > Unused clocks are NOT a configuration. > > They are by-product of the bootloader. You cannot rely on them. If > anything depends on them, you have a(nother) problem to solve. > >> >> Jerome and I have submitted patches to address the issue of >> CLK_IGNORE_UNUSED becoming ineffective. I originally planned to wait >> for progress on this patch and then incorporate Jerome's feedback before >> sending the V3 version. > I've provided a suggestion but this something happening in clock core. > I suggest that you split this out of your series so things that need to > go through Stephen are not mixed with Amlogic stuff. > > But again, you cannot rely on the state of clock just because it has > CLK_IGNORE_UNUSED: > > * Nothing says it is enabled to begin with > * Nothing says it will stay on if a consumer comes and goes > * ... and yes, it does not survive CCF usage checking down the road. > > It is unreliable and it is not meant to be more than that, AFAIK ok, I see what you mean, I will try to do that later. >> Hi Jerome, sorry if this caused any misunderstanding on your part; I >> will provide timely feedback moving forward. >> >> >>> >>> Best regards, >>> Martin > -- > Jerome