From: "Ondřej Jirman" <email@example.com> To: Chen-Yu Tsai <firstname.lastname@example.org> Cc: Alessandro Zummo <email@example.com>, Alexandre Belloni <firstname.lastname@example.org>, Rob Herring <email@example.com>, Mark Rutland <firstname.lastname@example.org>, Maxime Ripard <email@example.com>, firstname.lastname@example.org, devicetree <email@example.com>, linux-arm-kernel <firstname.lastname@example.org>, linux-kernel <email@example.com>, linux-sunxi <firstname.lastname@example.org> Subject: Re: [linux-sunxi] [PATCH 0/3] Add basic support for RTC on Allwinner H6 SoC Date: Mon, 15 Apr 2019 17:17:03 +0200 Message-ID: <email@example.com> (raw) In-Reply-To: <CAGb2v67XBGhoJWho16A3+2axBuTsY+SkYkg1hwQJ0XyPvPeoOw@mail.gmail.com> On Mon, Apr 15, 2019 at 10:35:47PM +0800, Chen-Yu Tsai wrote: > On Mon, Apr 15, 2019 at 10:22 PM 'Ondřej Jirman' via linux-sunxi > <firstname.lastname@example.org> wrote: > > > > Hi ChenYu, > > > > On Mon, Apr 15, 2019 at 04:18:12PM +0800, Chen-Yu Tsai wrote: > > > On Fri, Apr 12, 2019 at 8:07 PM megous via linux-sunxi > > > <email@example.com> wrote: > > > > > > > > From: Ondrej Jirman <firstname.lastname@example.org> > > > > > > > > I went through the datasheets for H6 and H5, and compared the differences. > > > > RTCs are largely similar, but not entirely compatible. Incompatibilities > > > > are in details not yet implemented by the rtc driver though. > > > > > > > > I also corrected the clock tree in H6 DTSI. > > > > > > Please also add DCXO clock input/output and XO clock input to the bindings > > > and DT, and also fix up the clock tree. You can skip them in the driver for > > > now, but please add a TODO. As long as you don't change the clock-output-name > > > of osc24M, everything should work as before. > > > > That's a bit confusing. There's no clock-output-name for osc24M, nor for input > > clock used in the dt-bindings or the driver. Perhaps you meant osc32k? Maybe > > I'm misunderstanding something? > > I meant the clock-output-names in the device node of the external 24M crystal. > > > If you look at the datasheet page 349, it looks like RTC provides "hosc" > > clock (to plls and the system) either from XO or DCXO oscillators. > > The default selection depends on the voltage level on external PAD. > > > > So based on what you wrote, I suggest these actual changes/names: > > > > 1) Add DT docs for HOSC clock provided at index 3: > > > > - 3: HOSC, 24MHz clock that clocks the PLLs and most of the SoC (H6 only) > > Correct. > > > 2) Add bindings description for "osc24M-dc", "osc24M-m" input clocks in > > addition to existing support for "osc32k". Name "osc24M-m" is based on > > X24MIN/MOUT pins and datasheet's "clk_24mxo" name. > > > > 3) The RTC driver would now just registers a fixed HOSC clock with a name > > gathered from the clock-output-names index 3 (if enabled by the new > > export_hosc flag - only enabled on H6). > > You don't need to do this part yet. Since the CCU drivers are hard-wired > (suprise) to use the global clock name "osc24M" as hosc source. The DT > references are only for show ATM, so it doesn't matter if you implement > the clocks in the RTC driver. Ah, so that's how it works. And that's what "clock parent rework" refers to! :) > However we want the DT to be correct, so that when we do get around to > doing it, we won't have to update the DT again. Ok, so I'll try to come up with a new set of patches, and we'll see if I'll get the description right. > It's up to you though. If you want to implement basic support, that's > fine by me. However you won't be able to test it without hacking the > CCU driver. > > After describing this, it seems that when we get to doing the clk parent > rework, we'll be in a bad situation if we don't get rtc changes in before > the CCU changes. Yeah. > > The driver would ignore the "osc24M-dc", "osc24M-m" input clocks. Or perhaps > > it could just support a case where only one of these are used and make it the > > only parent of the HOSC clock? > > They should just be DCXO and XO, based on the diagram. The names are local > to the RTC, so they don't need to be globally unique. Whatever matches the > datasheet is best. Ok. > > HOSC default source selection is done based on external PAD setup, and > > there's no need for runtime access/selection of HOSC source at the moment. > > Is it even possible to change it? Hmm. Looks like the answer is no: DCXO_CTRL_REG: - OSC_CLK_SRC_SEL bit: (Pad select) Read/Write column contains 'U' not (R/W) > > 4) In the future the RTC driver would be extended to support more refined > > setup/muxing/runtime selection of osc24M-dc/osc24M-m. PRCM driver would > > provide the osc24M-m clock, to be able for kernel to know how to gate it. > > > > The board's DTSI would have to link either "osc24M-dc", "osc24M-m" to nodes > > describing an external crystal (or to PRCM clock in the future). It's a boards > > choice on what crystals are actually used. 3 configs are possible - with one or > > two crystals, connected to either one of XIN/XOUT X24MIN/X24MOUT pins or both. > > AFAIK, osc24M-dc would link directly to the external crystal, while osc24M-m > would link to the external crystal first, then PRCM if it gets implemented. Ok. thank you, o. > > Would that work? > > > > DT would still probably need a re-work in the future, if the PRCM clock > > modeling the gate would be needed. > > Yeah. We'll deal with that when we get to it. > > > To summarize, the goal is to get the DT right the first time. > > Regards > ChenYu > > > > regards, > > o. > > > > > We just want the DT to describe what is actually there. For the XO input, > > > you could just directly reference the external crystal node. The gate for > > > it is likely somewhere in the PRCM block, which we don't have docs for. > > > > > > > There's a small detail here, that's not described absolutely correctly in > > > > DTSI, but the difference is not really that material. ext_osc32k is > > > > originally modelled as a fixed clock that feeds into RTC module, but in > > > > reality it's the RTC module that implements via its registers enabling and > > > > disabling of this oscillator/clock. > > > > > > > > Though: > > > > - there's no other possible user of ext_osc32k than RTC module > > > > - there's no other possible external configuration for the crystal > > > > circuit that would need to be handled in the dts per board > > > > > > > > So I guess, while the description is not perfect, this patch series still > > > > improves the current situation. Or maybe I'm misunderstanding something, > > > > and &ext_osc32k node just describes a fact that there's a crystal on > > > > the board. Then, everything is perhaps fine. :) > > > > > > Correct. The external clock nodes are modeling the crystal, not the internal > > > clock gate / distributor. > > > > > > Were the vendor to not include the crystal (for whatever reasons), the DT > > > should be able to describe it via the absence of the clock input, and the > > > driver should correctly use the internal (inaccurate) oscillator. I realize > > > the clocks property is required, and the driver doesn't handle this case > > > either, so we might have to fix that if it were to appear in the wild. > > > > > > > For now, the enable bit for this oscillator is toggled by the re-parenting > > > > code automatically, as needed. > > > > > > That's fine. No need to increase the clock tree depth. > > > > > > ChenYu > > > > > > > This patchset is necessary for implementing the WiFi/Bluetooth support > > > > on boards using H6 SoC. > > > > > > > > Please take a look. > > > > > > > > Thank you and regards, > > > > Ondrej Jirman > > > > > > > > Ondrej Jirman (3): > > > > dt-bindings: Add compatible for H6 RTC > > > > rtc: sun6i: Add support for H6 RTC > > > > arm64: dts: sun50i-h6: Add support for RTC and fix the clock tree > > > > > > > > .../devicetree/bindings/rtc/sun6i-rtc.txt | 1 + > > > > arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi | 30 +++++++------- > > > > drivers/rtc/rtc-sun6i.c | 40 ++++++++++++++++++- > > > > 3 files changed, 55 insertions(+), 16 deletions(-) > > > > > > > > -- > > > > 2.21.0 > > > > > > > > -- > > > > You received this message because you are subscribed to the Google Groups "linux-sunxi" group. > > > > To unsubscribe from this group and stop receiving emails from it, send an email to email@example.com. > > > > For more options, visit https://groups.google.com/d/optout. > > > > -- > > You received this message because you are subscribed to the Google Groups "linux-sunxi" group. > > To unsubscribe from this group and stop receiving emails from it, send an email to firstname.lastname@example.org. > > For more options, visit https://groups.google.com/d/optout.
next prev parent reply index Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-04-12 12:07 megous 2019-04-12 12:07 ` [PATCH 1/3] dt-bindings: Add compatible for H6 RTC megous 2019-08-05 10:16 ` [linux-sunxi] " Chen-Yu Tsai 2019-04-12 12:07 ` [PATCH 2/3] rtc: sun6i: Add support " megous 2019-08-05 10:16 ` [linux-sunxi] " Chen-Yu Tsai 2019-08-05 10:20 ` Ondřej Jirman 2019-08-05 10:45 ` Ondřej Jirman 2019-08-05 10:54 ` Chen-Yu Tsai 2019-08-05 11:10 ` Ondřej Jirman 2019-08-05 11:21 ` Chen-Yu Tsai 2019-08-05 12:16 ` Clément Péron 2019-04-12 12:07 ` [PATCH 3/3] arm64: dts: sun50i-h6: Add support for RTC and fix the clock tree megous 2019-04-15 8:18 ` [linux-sunxi] [PATCH 0/3] Add basic support for RTC on Allwinner H6 SoC Chen-Yu Tsai 2019-04-15 14:22 ` Ondřej Jirman 2019-04-15 14:33 ` Maxime Ripard 2019-04-15 14:39 ` Chen-Yu Tsai 2019-04-15 14:35 ` Chen-Yu Tsai 2019-04-15 15:17 ` Ondřej Jirman [this message] 2019-08-06 18:30 ` Ondřej Jirman 2019-08-06 22:27 ` Ondřej Jirman 2019-08-07 10:55 ` Alexandre Belloni 2019-08-08 5:48 ` Chen-Yu Tsai 2019-08-08 12:12 ` Ondřej Jirman 2019-08-08 23:39 ` Alexandre Belloni 2019-08-09 9:16 ` Ondřej Jirman
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