linux-kernel - Re: [PATCH 6/6] arm64: dts: khadas-vim3: add commented support for PCIe

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Date:   Wed, 11 Sep 2019 14:58:18 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Andrew Murray <andrew.murray@....com>
Cc:     khilman@...libre.com, bhelgaas@...gle.com,
        lorenzo.pieralisi@....com, yue.wang@...ogic.com, kishon@...com,
        repk@...plefau.lt, maz@...nel.org,
        linux-amlogic@...ts.infradead.org, linux-pci@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/6] arm64: dts: khadas-vim3: add commented support for
 PCIe

On 11/09/2019 14:50, Andrew Murray wrote:
> On Sun, Sep 08, 2019 at 01:42:58PM +0000, Neil Armstrong wrote:
>> The VIM3 on-board  MCU can mux the PCIe/USB3.0 shared differential
>> lines using a FUSB340TMX USB 3.1 SuperSpeed Data Switch between
>> an USB3.0 Type A connector and a M.2 Key M slot.
>> The PHY driving these differential lines is shared between
>> the USB3.0 controller and the PCIe Controller, thus only
>> a single controller can use it.
>>
>> The needed DT configuration when the MCU is configured to mux
>> the PCIe/USB3.0 differential lines to the M.2 Key M slot is
>> added commented and may uncommented to disable USB3.0 from the
> 
> *and may be*
> 
>> USB Complex and enable the PCIe controller.
>>
>> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
>> ---
>>  .../amlogic/meson-g12b-a311d-khadas-vim3.dts  | 22 +++++++++++++++++++
>>  .../amlogic/meson-g12b-s922x-khadas-vim3.dts  | 22 +++++++++++++++++++
>>  .../boot/dts/amlogic/meson-khadas-vim3.dtsi   |  4 ++++
>>  .../dts/amlogic/meson-sm1-khadas-vim3l.dts    | 22 +++++++++++++++++++
>>  4 files changed, 70 insertions(+)
>>
>> diff --git a/arch/arm64/boot/dts/amlogic/meson-g12b-a311d-khadas-vim3.dts b/arch/arm64/boot/dts/amlogic/meson-g12b-a311d-khadas-vim3.dts
>> index 3a6a1e0c1e32..0577b1435cbb 100644
>> --- a/arch/arm64/boot/dts/amlogic/meson-g12b-a311d-khadas-vim3.dts
>> +++ b/arch/arm64/boot/dts/amlogic/meson-g12b-a311d-khadas-vim3.dts
>> @@ -14,3 +14,25 @@
>>  / {
>>  	compatible = "khadas,vim3", "amlogic,a311d", "amlogic,g12b";
>>  };
>> +
>> +/*
>> + * The VIM3 on-board  MCU can mux the PCIe/USB3.0 shared differential
>> + * lines using a FUSB340TMX USB 3.1 SuperSpeed Data Switch between
>> + * an USB3.0 Type A connector and a M.2 Key M slot.
>> + * The PHY driving these differential lines is shared between
>> + * the USB3.0 controller and the PCIe Controller, thus only
>> + * a single controller can use it.
>> + * If the MCU is configured to mux the PCIe/USB3.0 differential lines
>> + * to the M.2 Key M slot, uncomment the following block to disable
>> + * USB3.0 from the USB Complex and enable the PCIe controller.
>> + */
>> +/*
>> +&pcie {
>> +	status = "okay";
>> +};
>> +
>> +&usb {
>> +	phys = <&usb2_phy0>, <&usb2_phy1>;
>> +	phy-names = "usb2-phy0", "usb2-phy1";
>> +};
> 
> I assume there is no way other way to determine from the hardware which way
> the mux is set?

No, it would be simpler :-/ The MUX is on-board and the MCU drives the MUX selection.

You can look at the https://dl.khadas.com/Hardware/VIM3/Schematic/VIM3_V11_Sch.pdf
The PCIE_EN signal is driven by the STM8S MCU.

> 
> Otherwise phy_g12a_usb3_pcie_xlate could determine the hardware mode, and
> reject the phy instance with the wrong mode. Thus resulting in either the
> PCI or USB to fail their probe. And avoiding the need to modify the DT on
> boot.

Yep, it would have been simpler this way. Maybe a board vendor will set a gpio ?
who knows, but for actual boards it's static or with 0ohm resistors, and for the
VIM3 we only know by asking the MCU.

Maybe we could add a fake PHY as a MCU MFD subdevice, wrapping calls to the
right PHY. But for now the MCU has no upstream driver anyway.

Neil

> 
> Thanks,
> 
> Andrew Murray
> 
>> + */
>> diff --git a/arch/arm64/boot/dts/amlogic/meson-g12b-s922x-khadas-vim3.dts b/arch/arm64/boot/dts/amlogic/meson-g12b-s922x-khadas-vim3.dts
>> index b73deb282120..1ef5c2f04f67 100644
>> --- a/arch/arm64/boot/dts/amlogic/meson-g12b-s922x-khadas-vim3.dts
>> +++ b/arch/arm64/boot/dts/amlogic/meson-g12b-s922x-khadas-vim3.dts
>> @@ -14,3 +14,25 @@
>>  / {
>>  	compatible = "khadas,vim3", "amlogic,s922x", "amlogic,g12b";
>>  };
>> +
>> +/*
>> + * The VIM3 on-board  MCU can mux the PCIe/USB3.0 shared differential
>> + * lines using a FUSB340TMX USB 3.1 SuperSpeed Data Switch between
>> + * an USB3.0 Type A connector and a M.2 Key M slot.
>> + * The PHY driving these differential lines is shared between
>> + * the USB3.0 controller and the PCIe Controller, thus only
>> + * a single controller can use it.
>> + * If the MCU is configured to mux the PCIe/USB3.0 differential lines
>> + * to the M.2 Key M slot, uncomment the following block to disable
>> + * USB3.0 from the USB Complex and enable the PCIe controller.
>> + */
>> +/*
>> +&pcie {
>> +	status = "okay";
>> +};
>> +
>> +&usb {
>> +	phys = <&usb2_phy0>, <&usb2_phy1>;
>> +	phy-names = "usb2-phy0", "usb2-phy1";
>> +};
>> + */
>> diff --git a/arch/arm64/boot/dts/amlogic/meson-khadas-vim3.dtsi b/arch/arm64/boot/dts/amlogic/meson-khadas-vim3.dtsi
>> index 8647da7d6609..eac5720dc15f 100644
>> --- a/arch/arm64/boot/dts/amlogic/meson-khadas-vim3.dtsi
>> +++ b/arch/arm64/boot/dts/amlogic/meson-khadas-vim3.dtsi
>> @@ -246,6 +246,10 @@
>>  	linux,rc-map-name = "rc-khadas";
>>  };
>>  
>> +&pcie {
>> +	reset-gpios = <&gpio GPIOA_8 GPIO_ACTIVE_LOW>;
>> +};
>> +
>>  &pwm_ef {
>>          status = "okay";
>>          pinctrl-0 = <&pwm_e_pins>;
>> diff --git a/arch/arm64/boot/dts/amlogic/meson-sm1-khadas-vim3l.dts b/arch/arm64/boot/dts/amlogic/meson-sm1-khadas-vim3l.dts
>> index 5233bd7cacfb..d9c7cbedce53 100644
>> --- a/arch/arm64/boot/dts/amlogic/meson-sm1-khadas-vim3l.dts
>> +++ b/arch/arm64/boot/dts/amlogic/meson-sm1-khadas-vim3l.dts
>> @@ -68,3 +68,25 @@
>>  	clock-names = "clkin1";
>>  	status = "okay";
>>  };
>> +
>> +/*
>> + * The VIM3 on-board  MCU can mux the PCIe/USB3.0 shared differential
>> + * lines using a FUSB340TMX USB 3.1 SuperSpeed Data Switch between
>> + * an USB3.0 Type A connector and a M.2 Key M slot.
>> + * The PHY driving these differential lines is shared between
>> + * the USB3.0 controller and the PCIe Controller, thus only
>> + * a single controller can use it.
>> + * If the MCU is configured to mux the PCIe/USB3.0 differential lines
>> + * to the M.2 Key M slot, uncomment the following block to disable
>> + * USB3.0 from the USB Complex and enable the PCIe controller.
>> + */
>> +/*
>> +&pcie {
>> +	status = "okay";
>> +};
>> +
>> +&usb {
>> +	phys = <&usb2_phy0>, <&usb2_phy1>;
>> +	phy-names = "usb2-phy0", "usb2-phy1";
>> +};
>> + */
>> -- 
>> 2.17.1
>>