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Message-ID: <CAA8EJpoQO7=v8QWeH8MAgX4uU=m4VJqfC3J5PKyySM2TBcHWiw@mail.gmail.com>
Date: Tue, 29 Oct 2024 16:18:44 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Jie Luo <quic_luoj@...cinc.com>
Cc: Bjorn Andersson <andersson@...nel.org>, Michael Turquette <mturquette@...libre.com>,
Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
Konrad Dybcio <konradybcio@...nel.org>, linux-arm-msm@...r.kernel.org,
linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
quic_kkumarcs@...cinc.com, quic_suruchia@...cinc.com, quic_pavir@...cinc.com,
quic_linchen@...cinc.com, quic_leiwei@...cinc.com,
bartosz.golaszewski@...aro.org, srinivas.kandagatla@...aro.org
Subject: Re: [PATCH v5 4/4] arm64: dts: qcom: Add CMN PLL node for IPQ9574 SoC
On Tue, 29 Oct 2024 at 15:31, Jie Luo <quic_luoj@...cinc.com> wrote:
>
>
>
> On 10/28/2024 11:39 PM, Dmitry Baryshkov wrote:
> > On Mon, Oct 28, 2024 at 10:04:11PM +0800, Luo Jie wrote:
> >> The CMN PLL clock controller allows selection of an input clock rate
> >> from a defined set of input clock rates. It in-turn supplies fixed
> >> rate output clocks to the hardware blocks that provide the ethernet
> >> functions such as PPE (Packet Process Engine) and connected switch or
> >> PHY, and to GCC.
> >>
> >> The reference clock of CMN PLL is routed from XO to the CMN PLL through
> >> the internal WiFi block.
> >> .XO (48 MHZ or 96 MHZ)-->WiFi (multiplier/divider)-->48 MHZ to CMN PLL.
> >>
> >> The reference input clock from WiFi to CMN PLL is fully controlled by
> >> the bootstrap pins which select the XO frequency (48 MHZ or 96 MHZ).
> >> Based on this frequency, the divider in the internal Wi-Fi block is
> >> automatically configured by hardware (1 for 48 MHZ, 2 for 96 MHZ), to
> >> ensure output clock to CMN PLL is 48 MHZ.
> >>
> >> Signed-off-by: Luo Jie <quic_luoj@...cinc.com>
> >> ---
> >> arch/arm64/boot/dts/qcom/ipq9574-rdp-common.dtsi | 16 ++++++++++++++-
> >> arch/arm64/boot/dts/qcom/ipq9574.dtsi | 26 +++++++++++++++++++++++-
> >> 2 files changed, 40 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/arch/arm64/boot/dts/qcom/ipq9574-rdp-common.dtsi b/arch/arm64/boot/dts/qcom/ipq9574-rdp-common.dtsi
> >> index 91e104b0f865..f026c2a9d0c0 100644
> >> --- a/arch/arm64/boot/dts/qcom/ipq9574-rdp-common.dtsi
> >> +++ b/arch/arm64/boot/dts/qcom/ipq9574-rdp-common.dtsi
> >> @@ -3,7 +3,7 @@
> >> * IPQ9574 RDP board common device tree source
> >> *
> >> * Copyright (c) 2020-2021 The Linux Foundation. All rights reserved.
> >> - * Copyright (c) 2023, Qualcomm Innovation Center, Inc. All rights reserved.
> >> + * Copyright (c) 2023-2024, Qualcomm Innovation Center, Inc. All rights reserved.
> >> */
> >>
> >> /dts-v1/;
> >> @@ -164,6 +164,20 @@ &usb3 {
> >> status = "okay";
> >> };
> >>
> >> +/*
> >> + * The bootstrap pins for the board select the XO clock frequency,
> >> + * which automatically enables the right dividers to ensure the
> >> + * reference clock output to CMNPLL is 48 MHZ.
> >> + */
> >> +&cmn_pll_ref_clk {
> >> + clock-div = <1>;
> >> + clock-mult = <1>;
> >> +};
> >> +
> >> &xo_board_clk {
> >> clock-frequency = <24000000>;
> >> };
> >> +
> >> +&xo_clk {
> >> + clock-frequency = <48000000>;
> >> +};
> >> diff --git a/arch/arm64/boot/dts/qcom/ipq9574.dtsi b/arch/arm64/boot/dts/qcom/ipq9574.dtsi
> >> index 14c7b3a78442..ad9cdb1f76db 100644
> >> --- a/arch/arm64/boot/dts/qcom/ipq9574.dtsi
> >> +++ b/arch/arm64/boot/dts/qcom/ipq9574.dtsi
> >> @@ -3,10 +3,11 @@
> >> * IPQ9574 SoC device tree source
> >> *
> >> * Copyright (c) 2020-2021 The Linux Foundation. All rights reserved.
> >> - * Copyright (c) 2023, Qualcomm Innovation Center, Inc. All rights reserved.
> >> + * Copyright (c) 2023-2024, Qualcomm Innovation Center, Inc. All rights reserved.
> >> */
> >>
> >> #include <dt-bindings/clock/qcom,apss-ipq.h>
> >> +#include <dt-bindings/clock/qcom,ipq-cmn-pll.h>
> >> #include <dt-bindings/clock/qcom,ipq9574-gcc.h>
> >> #include <dt-bindings/interconnect/qcom,ipq9574.h>
> >> #include <dt-bindings/interrupt-controller/arm-gic.h>
> >> @@ -19,6 +20,12 @@ / {
> >> #size-cells = <2>;
> >>
> >> clocks {
> >> + cmn_pll_ref_clk: cmn-pll-ref-clk {
> >> + compatible = "fixed-factor-clock";
> >> + clocks = <&xo_clk>;
> >> + #clock-cells = <0>;
> >> + };
> >> +
> >> sleep_clk: sleep-clk {
> >> compatible = "fixed-clock";
> >> #clock-cells = <0>;
> >> @@ -28,6 +35,11 @@ xo_board_clk: xo-board-clk {
> >> compatible = "fixed-clock";
> >> #clock-cells = <0>;
> >> };
> >> +
> >> + xo_clk: xo-clk {
> >> + compatible = "fixed-clock";
> >> + #clock-cells = <0>;
> >> + };
> >
> > What is the difference between xo_clk and xo_board_clk? Are there two
> > different crystals?
>
> The xo_board_clk of 24 MHZ is generated by applying another divider in
> HW (by 2), on top of the same 48 MHZ clock output from internal Wi-Fi.
>
> XO (48 MHZ or 96 MHZ)-->WiFi (mul/div)-->48 MHZ-->fixed factor divider 2
> by HW ---> xo_board_clk (24 MHZ)
>
> We may need to correct its clock chain representation. We will update
> xo_board_clk as a fixed factor (div by 2) clock, and refer to the 48 MHZ
> input clock, using a separate patch after the CMN PLL patch series
> review is concluded. Hope this approach is fine.
Yes, please. Don't try to 'shortcut' the hardware description.
Describing the actual hardware is the best way to work.
--
With best wishes
Dmitry
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