Messages in this thread | | | Date | Mon, 19 Jun 2023 09:45:27 +0200 | Subject | Re: [PATCH v2 3/5] media: mediatek: vcodec: Read HW active status from clock | From | AngeloGioacchino Del Regno <> |
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Il 15/06/23 19:40, Stephen Boyd ha scritto: > Quoting AngeloGioacchino Del Regno (2023-06-15 00:30:56) >> Il 15/06/23 02:40, Stephen Boyd ha scritto: >>> Quoting AngeloGioacchino Del Regno (2023-06-14 01:13:43) >>>> Il 12/06/23 21:19, Stephen Boyd ha scritto: >>>>> Quoting AngeloGioacchino Del Regno (2023-06-09 00:42:13) >>>>>> Il 09/06/23 01:56, Stephen Boyd ha scritto: >>>>>>> Quoting AngeloGioacchino Del Regno (2023-06-08 02:01:58) >>>>>>>> Il 08/06/23 10:12, Chen-Yu Tsai ha scritto: >>>>>>>>> On Thu, Jun 8, 2023 at 4:57 AM Nícolas F. R. A. Prado >>>>>>>>> <nfraprado@collabora.com> wrote: >>>>>> >>>>>> The firmware gives an indication of "boot done", but that's for the "core" part >>>>>> of the vcodec... then it manages this clock internally to enable/disable the >>>>>> "compute" IP of the decoder. >>>>>> >>>>>> As far as I know (and I've been researching about this) the firmware will not >>>>>> give any "decoder powered, clocked - ready to get data" indication, and the >>>>>> only way that we have to judge whether it is in this specific state or not is >>>>>> to check if the "VDEC_ACTIVE" clock got enabled by the firmware. >>>>> >>>>> Is Linux ever going to use clk consumer APIs like clk_enable/clk_disable >>>>> on this VDEC_ACTIVE clk? If the answer is no, then there isn't any >>>>> reason to put it in the clk framework, and probably syscon is the way to >>>>> go for now. >>>>> >>>> >>>> Not for the current platform, but that may change in future SoCs... we're not sure. >>> >>> If you're not using the clk consumer APIs then it shouldn't be a clk. >>> >>>> >>>>> Another approach could be to wait for some amount of time after telling >>>>> firmware to power up and assume the hardware is active. >>>>> >>>> >>>> That would be highly error prone though. Expecting that the HW is alive means that >>>> we're 100% sure that both firmware and driver are doing the right thing at every >>>> moment, which is something that we'd like to assume but, realistically, for safety >>>> reasons we just don't. >>>> >>>> Should we anyway go for a syscon *now* and then change it to a clock later, if any >>>> new platform needs this as a clock? >>> >>> Yeah. Or implement this as a power domain and have it read the register >>> directly waiting to return from the power_on()? >> >> A power domain would force us to incorrectly describe the hardware in the bindings >> though, I think... so, Nícolas, please, let's go for a syscon at this point, as it > > You don't have to add the power domain in DT, do you? You can populate a > power domain in software directly? >
Right. I didn't evaluate that possibility at all. Looks good!
>> really looks like being the only viable option. >> >> Stephen, many thanks for the valuable suggestions and the nice conversation. >> >
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