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Date: Tue, 22 Jan 2019 17:09:30 -0800 From: Bjorn Andersson <bjorn.andersson@...aro.org> To: Doug Anderson <dianders@...omium.org> Cc: Andy Gross <andy.gross@...aro.org>, David Brown <david.brown@...aro.org>, Sibi Sankar <sibis@...eaurora.org>, Rob Herring <robh+dt@...nel.org>, Mark Rutland <mark.rutland@....com>, linux-arm-msm <linux-arm-msm@...r.kernel.org>, devicetree@...r.kernel.org, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v3 03/10] arm64: dts: sdm845: Introduce ADSP and CDSP PAS nodes On Tue 22 Jan 16:40 PST 2019, Doug Anderson wrote: > Hi, > > On Tue, Jan 22, 2019 at 4:26 PM Bjorn Andersson > <bjorn.andersson@...aro.org> wrote: > > > > + clocks = <&xo_board>; > > > > + clock-names = "xo"; > > > > > > I've found that nearly all the places that refer to xo_board are wrong > > > and should actually point to '<&rpmhcc RPMH_CXO_CLK>'. Maybe yours > > > should too? > > > > > > > Yes, xo_board is a fake clock representing the 19.2MHz clock feeding the > > cxo (or cxo2) pad of the SoC. So you're definitely right in that this > > should be referencing the actual 19.2MHz clock. > > > > We've kept referring to this as xo_board, as we don't handle probe > > deferral when gcc will probe earlier than rpmcc in the boot and for > > other non-clock drivers the fear of actually hitting 0 on the refcounter > > for this (you don't want to disable the cxo while running the system). > > Note that, as defined in the device tree, "xo_board" is actually 38.4. > IIUC that is not actually a fake/bogus clock but represents the actual > crystal on the board. There's a divide by 2 in the CPU though so most > peripherals consider "xo" as 19.2. > There's the 38.4MHz XO connected to the PMIC, but the signal going into the CXO_IN pad of the SoC is supposed to come from LNBBCLK1 and be 19.2MHz. > ...OK, confirmed. The actual RF_XO_CLK pin on the board is truly > connected to 38.4. > And the three RF clocks from the PMIC are all ticking at 38.4MHz. The "xo" I need here is the LNBBCLK1 (RPMH_CXO_CLK in clk-rpmh), for the purpose of preventing the root clock to be turned off if apps goes to suspend while the modem is booting, before it has had a chance to tell RPM(h) that it needs it to be on. Regards, Bjorn
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