linux-kernel - Re: [PATCH V4 2/4] arm64: dts: sc7280: Add QUPv3 wrapper

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Message-ID: <YP7cmkayoajJ+1yj@google.com>
Date:   Mon, 26 Jul 2021 09:02:34 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Rajesh Patil <rajpat@...eaurora.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, rnayak@...eaurora.org,
        saiprakash.ranjan@...eaurora.org, msavaliy@....qualcomm.com,
        skakit@...eaurora.org, Roja Rani Yarubandi <rojay@...eaurora.org>
Subject: Re: [PATCH V4 2/4] arm64: dts: sc7280: Add QUPv3 wrapper_0 nodes

On Mon, Jul 26, 2021 at 07:10:45PM +0530, Rajesh Patil wrote:
> From: Roja Rani Yarubandi <rojay@...eaurora.org>
> 
> Add QUPv3 wrapper_0 DT nodes for SC7280 SoC.
> 
> Signed-off-by: Roja Rani Yarubandi <rojay@...eaurora.org>
> Signed-off-by: Rajesh Patil <rajpat@...eaurora.org>
> ---
> Changes in V4:
>  - As per Bjorn's comment, added QUP Wrapper_0 nodes
>    other than debug-uart node
>  - Dropped interconnect votes for wrapper_0 node
> 
> Changes in V3:
>  - Broken the huge V2 patch into 3 smaller patches.
>    1. QSPI DT nodes
>    2. QUP wrapper_0 DT nodes
>    3. QUP wrapper_1 DT nodes
> 
> Changes in V2:
>  - As per Doug's comments removed pinmux/pinconf subnodes.
>  - As per Doug's comments split of SPI, UART nodes has been done.
>  - Moved QSPI node before aps_smmu as per the order.
> 
>  arch/arm64/boot/dts/qcom/sc7280-idp.dts |  84 ++++
>  arch/arm64/boot/dts/qcom/sc7280.dtsi    | 720 ++++++++++++++++++++++++++++++++
>  2 files changed, 804 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sc7280-idp.dts b/arch/arm64/boot/dts/qcom/sc7280-idp.dts
> index b0bfd8e..f63cf51 100644
> --- a/arch/arm64/boot/dts/qcom/sc7280-idp.dts
> +++ b/arch/arm64/boot/dts/qcom/sc7280-idp.dts
> @@ -358,6 +358,16 @@
>  	vdda18-supply = <&vreg_l1c_1p8>;
>  };
>  
> +&uart7 {
> +	status = "okay";
> +
> +	/delete-property/interrupts;
> +	interrupts-extended = <&intc GIC_SPI 608 IRQ_TYPE_LEVEL_HIGH>,
> +				<&tlmm 31 IRQ_TYPE_EDGE_FALLING>;
> +	pinctrl-names = "default", "sleep";
> +	pinctrl-1 = <&qup_uart7_sleep_cts>, <&qup_uart7_sleep_rts>, <&qup_uart7_sleep_tx>, <&qup_uart7_sleep_rx>;
> +};
> +
>  /* PINCTRL - additions to nodes defined in sc7280.dtsi */
>  
>  &qspi_cs0 {
> @@ -428,3 +438,77 @@
>  		bias-pull-up;
>  	};
>  };
> +&qup_uart7_cts {
> +	/*
> +	 * Configure a pull-down on CTS to match the pull of
> +	 * the Bluetooth module.
> +	 */
> +	bias-pull-down;
> +};
> +
> +&qup_uart7_rts {
> +	/* We'll drive RTS, so no pull */
> +	drive-strength = <2>;
> +	bias-disable;
> +};
> +
> +&qup_uart7_tx {
> +	/* We'll drive TX, so no pull */
> +	drive-strength = <2>;
> +	bias-disable;
> +};
> +
> +&qup_uart7_rx {
> +	/*
> +	 * Configure a pull-up on RX. This is needed to avoid
> +	 * garbage data when the TX pin of the Bluetooth module is
> +	 * in tri-state (module powered off or not driving the
> +	 * signal yet).
> +	 */
> +	bias-pull-up;
> +};
> +
> +&tlmm {
> +	qup_uart7_sleep_cts: qup-uart7-sleep-cts {
> +		pins = "gpio28";
> +		function = "gpio";
> +		/*
> +		 * Configure a pull-down on CTS to match the pull of
> +		 * the Bluetooth module.
> +		 */
> +		bias-pull-down;
> +	};
> +
> +	qup_uart7_sleep_rts: qup-uart7-sleep-rts {
> +		pins = "gpio29";
> +		function = "gpio";
> +		/*
> +		 * Configure pull-down on RTS. As RTS is active low
> +		 * signal, pull it low to indicate the BT SoC that it
> +		 * can wakeup the system anytime from suspend state by
> +		 * pulling RX low (by sending wakeup bytes).
> +		 */
> +		bias-pull-down;
> +	};
> +
> +	qup_uart7_sleep_tx: qup-uart7-sleep-tx {
> +		pins = "gpio30";
> +		function = "gpio";
> +		/*
> +		 * Configure pull-up on TX when it isn't actively driven
> +		 * to prevent BT SoC from receiving garbage during sleep.
> +		 */
> +		bias-pull-up;
> +	};
> +
> +	qup_uart7_sleep_rx: qup-uart7-sleep-rx {
> +		pins = "gpio31";
> +		function = "gpio";
> +		/*
> +		 * Configure a pull-up on RX. This is needed to avoid
> +		 * garbage data when the TX pin of the Bluetooth module
> +		 * is floating which may cause spurious wakeups.
> +		 */
> +		bias-pull-up;
> +	};
> +};

How the patches of this series are split strikes me as a bit odd. Supposedly
this patch adds the QUPv3 wrapper_0 DT nodes for the SC7280, however the
above is the pin configuration for the Bluetooth UART of the SC7280 IDP board.
I don't see a good reason why that should be part of this patch. It should be
a separate change whose subject indicates that it configures the Bluetooth UART
of the SC7280 IDP.

Without this conflation of SoC and board DT it would seem perfectly reasonable
to squash this patch and '[4/4] arm64: dts: sc7280: Add QUPv3 wrapper_1 nodes'
into a single one, they are essentially doing the same thing, I see no need to
have different patches for the wrapper 0 and 1 nodes.