Messages in this thread | | | Date | Thu, 15 Jun 2023 09:30:56 +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 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 really looks like being the only viable option.
Stephen, many thanks for the valuable suggestions and the nice conversation.
Cheers! Angelo
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