Re: [PATCH V5 10/16] dt-bindings: PCI: tegra: Add device tree support for T194

[Rob Herring <robh@kernel.org>]

On Wed, Apr 24, 2019 at 10:49:58AM +0530, Vidya Sagar wrote:
> Add support for Tegra194 PCIe controllers. These controllers are based
> on Synopsys DesignWare core IP.
> 
> Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
> ---
> Changes since [v4]:
> * None
> 
> Changes since [v3]:
> * None
> 
> Changes since [v2]:
> * Using only 'Cx' (x-being controller number) format to represent a controller
> * Changed to 'value: description' format where applicable
> * Changed 'nvidia,init-speed' to 'nvidia,init-link-speed'
> * Provided more documentation for 'nvidia,init-link-speed' property
> * Changed 'nvidia,pex-wake' to 'nvidia,wake-gpios'
> 
> Changes since [v1]:
> * Added documentation for 'power-domains' property
> * Removed 'window1' and 'window2' properties
> * Removed '_clk' and '_rst' from clock and reset names
> * Dropped 'pcie' from phy-names
> * Added entry for BPMP-FW handle
> * Removed offsets for some of the registers and added them in code and would be pickedup based on
>   controller ID
> * Changed 'nvidia,max-speed' to 'max-link-speed' and is made as an optional
> * Changed 'nvidia,disable-clock-request' to 'supports-clkreq' with inverted operation
> * Added more documentation for 'nvidia,update-fc-fixup' property
> * Removed 'nvidia,enable-power-down' and 'nvidia,plat-gpios' properties
> * Added '-us' to all properties that represent time in microseconds
> * Moved P2U documentation to a separate file
> 
>  .../bindings/pci/nvidia,tegra194-pcie.txt     | 187 ++++++++++++++++++
>  1 file changed, 187 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/pci/nvidia,tegra194-pcie.txt
> 
> diff --git a/Documentation/devicetree/bindings/pci/nvidia,tegra194-pcie.txt b/Documentation/devicetree/bindings/pci/nvidia,tegra194-pcie.txt
> new file mode 100644
> index 000000000000..208dff126108
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pci/nvidia,tegra194-pcie.txt
> @@ -0,0 +1,187 @@
> +NVIDIA Tegra PCIe controller (Synopsys DesignWare Core based)
> +
> +This PCIe host controller is based on the Synopsis Designware PCIe IP
> +and thus inherits all the common properties defined in designware-pcie.txt.
> +
> +Required properties:
> +- compatible: For Tegra19x, must contain "nvidia,tegra194-pcie".
> +- device_type: Must be "pci"
> +- power-domains: A phandle to the node that controls power to the respective
> +  PCIe controller and a specifier name for the PCIe controller. Following are
> +  the specifiers for the different PCIe controllers
> +    TEGRA194_POWER_DOMAIN_PCIEX8B: C0
> +    TEGRA194_POWER_DOMAIN_PCIEX1A: C1
> +    TEGRA194_POWER_DOMAIN_PCIEX1A: C2
> +    TEGRA194_POWER_DOMAIN_PCIEX1A: C3
> +    TEGRA194_POWER_DOMAIN_PCIEX4A: C4
> +    TEGRA194_POWER_DOMAIN_PCIEX8A: C5
> +  these specifiers are defined in
> +  "include/dt-bindings/power/tegra194-powergate.h" file.
> +- reg: A list of physical base address and length for each set of controller
> +  registers. Must contain an entry for each entry in the reg-names property.
> +- reg-names: Must include the following entries:
> +  "appl": Controller's application logic registers
> +  "config": As per the definition in designware-pcie.txt
> +  "atu_dma": iATU and DMA registers. This is where the iATU (internal Address
> +             Translation Unit) registers of the PCIe core are made available
> +             fow SW access.
> +  "dbi": The aperture where root port's own configuration registers are
> +         available
> +- interrupts: A list of interrupt outputs of the controller. Must contain an
> +  entry for each entry in the interrupt-names property.
> +- interrupt-names: Must include the following entries:
> +  "intr": The Tegra interrupt that is asserted for controller interrupts
> +  "msi": The Tegra interrupt that is asserted when an MSI is received
> +- bus-range: Range of bus numbers associated with this controller
> +- #address-cells: Address representation for root ports (must be 3)
> +  - cell 0 specifies the bus and device numbers of the root port:
> +    [23:16]: bus number
> +    [15:11]: device number
> +  - cell 1 denotes the upper 32 address bits and should be 0
> +  - cell 2 contains the lower 32 address bits and is used to translate to the
> +    CPU address space
> +- #size-cells: Size representation for root ports (must be 2)
> +- ranges: Describes the translation of addresses for root ports and standard
> +  PCI regions. The entries must be 7 cells each, where the first three cells
> +  correspond to the address as described for the #address-cells property
> +  above, the fourth and fifth cells are for the physical CPU address to
> +  translate to and the sixth and seventh cells are as described for the
> +  #size-cells property above.
> +  - Entries setup the mapping for the standard I/O, memory and
> +    prefetchable PCI regions. The first cell determines the type of region
> +    that is setup:
> +    - 0x81000000: I/O memory region
> +    - 0x82000000: non-prefetchable memory region
> +    - 0xc2000000: prefetchable memory region
> +  Please refer to the standard PCI bus binding document for a more detailed
> +  explanation.
> +- #interrupt-cells: Size representation for interrupts (must be 1)
> +- interrupt-map-mask and interrupt-map: Standard PCI IRQ mapping properties
> +  Please refer to the standard PCI bus binding document for a more detailed
> +  explanation.
> +- clocks: Must contain an entry for each entry in clock-names.
> +  See ../clocks/clock-bindings.txt for details.
> +- clock-names: Must include the following entries:
> +  - core
> +- resets: Must contain an entry for each entry in reset-names.
> +  See ../reset/reset.txt for details.
> +- reset-names: Must include the following entries:
> +  - core_apb
> +  - core
> +- phys: Must contain a phandle to P2U PHY for each entry in phy-names.
> +- phy-names: Must include an entry for each active lane.
> +  "p2u-N": where N ranges from 0 to one less than the total number of lanes
> +- nvidia,bpmp: Must contain a phandle to BPMP controller node.
> +- nvidia,controller-id : Controller specific ID
> +    0: C0
> +    1: C1
> +    2: C2
> +    3: C3
> +    4: C4
> +    5: C5

We don't normal put device indexes into DT. Why do you need this. 
Perhaps for accessing the BPMP? If so, make nvidia,bpmp a phandle+cell.

> +- vddio-pex-ctl-supply: Regulator supply for PCIe side band signals
> +
> +Optional properties:
> +- max-link-speed: Limits controllers max speed to this value. For more info,
> +    please refer to Documentation/devicetree/bindings/pci/pci.txt file.

No need to define the property again. Just reference the definition and 
define any constraints not in the base def. For example, what's the max 
value?

> +- nvidia,init-link-speed: Limits controllers init speed to this value. It means
> +    that link is brought up to the speed specified by this property initially by
> +    hardware (provided connected end point also supports that). Since the
> +    controller continues to advertise maximum supported link speed set up
> +    through max-link-speed property (Gen-4 if max-link-speed is not present) in
> +    its configuration space, software can take link the desired speed at a later
> +    point of time by spec defined speed change mechanism.
> +    1: Gen-1 (2.5 GT/s)
> +    2: Gen-2 (5 GT/s)
> +    3: Gen-3 (8 GT/s)
> +    4: Gen-4 (16 GT/s)

Why not just set things to the max? Power savingss? If so, you're going 
to want to change speeds at run-time and I don't see how boot-time 
setting really matters.

If we do need this, then I think it should be common.

> +- nvidia,disable-aspm-states: Controls advertisement of ASPM states
> +    bit-0 to '1': Disables advertisement of ASPM-L0s
> +    bit-1 to '1': Disables advertisement of ASPM-L1. This also disables
> +                   advertisement of ASPM-L1.1 and ASPM-L1.2
> +    bit-2 to '1': Disables advertisement of ASPM-L1.1
> +    bit-3 to '1': Disables advertisement of ASPM-L1.2

Can't this cover what 'supports-clkreq' does?

I think this should be common property. We already have a Rockchip 
property to disable L0s.

Also, just use 0x1, 0x2, 0x4 instead of "bit-N to '1'"

> +- supports-clkreq: Refer to Documentation/devicetree/bindings/pci/pci.txt
> +- nvidia,update-fc-fixup: This is a boolean property and needs to be present to
> +    improve perf when a platform is designed in such a way that it satisfies at
> +    least one of the following conditions thereby enabling root port to
> +    exchange optimum number of FC (Flow Control) credits with downstream devices
> +    1. If C0/C4/C5 run at x1/x2 link widths (irrespective of speed and MPS)
> +    2. If C0/C1/C2/C3/C4/C5 operate at their respective max link widths and
> +       a) speed is Gen-2 and MPS is 256B
> +       b) speed is >= Gen-3 with any MPS
> +- "nvidia,wake-gpios": Add PEX_WAKE GPIO pin. It contains phandle to GPIO
> +    controller followed by GPIO specifier.

Seems like the same issue as this discussion:

https://lkml.org/lkml/2019/2/24/69

I'd drop this until this is solved in a common way.

> +    Refer ../gpio/nvidia,tegra186-gpio.txt for more info.
> +- "nvidia,aspm-cmrt-us": Common Mode Restore time for proper operation of ASPM
> +   to be specified in microseconds
> +- "nvidia,aspm-pwr-on-t-us": Power On time for proper operation of ASPM to be
> +   specified in microseconds
> +- "nvidia,aspm-l0s-entrance-latency-us": ASPM L0s entrance latency to be
> +   specified in microseconds
> +
> +Examples:
> +=========
> +
> +Tegra194:
> +--------
> +
> +SoC DTSI:
> +
> +	pcie@14180000 {
> +		compatible = "nvidia,tegra194-pcie", "snps,dw-pcie";
> +		power-domains = <&bpmp TEGRA194_POWER_DOMAIN_PCIEX8B>;
> +		reg = <0x00 0x14180000 0x0 0x00020000   /* appl registers (128K)      */
> +		       0x00 0x38000000 0x0 0x00040000   /* configuration space (256K) */
> +		       0x00 0x38040000 0x0 0x00040000>; /* iATU_DMA reg space (256K)  */
> +		reg-names = "appl", "config", "atu_dma";
> +
> +		status = "disabled";

Don't show status in examples.

> +
> +		#address-cells = <3>;
> +		#size-cells = <2>;
> +		device_type = "pci";
> +		num-lanes = <8>;
> +		linux,pci-domain = <0>;
> +
> +		clocks = <&bpmp TEGRA194_CLK_PEX0_CORE_0>;
> +		clock-names = "core";
> +
> +		resets = <&bpmp TEGRA194_RESET_PEX0_CORE_0_APB>,
> +			 <&bpmp TEGRA194_RESET_PEX0_CORE_0>;
> +		reset-names = "core_apb", "core";
> +
> +		interrupts = <GIC_SPI 72 IRQ_TYPE_LEVEL_HIGH>,	/* controller interrupt */
> +			     <GIC_SPI 73 IRQ_TYPE_LEVEL_HIGH>;	/* MSI interrupt */
> +		interrupt-names = "intr", "msi";
> +
> +		#interrupt-cells = <1>;
> +		interrupt-map-mask = <0 0 0 0>;
> +		interrupt-map = <0 0 0 0 &gic 0 72 0x04>;
> +
> +		nvidia,bpmp = <&bpmp>;
> +
> +		supports-clkreq;
> +		nvidia,disable-aspm-states = <0xf>;
> +		nvidia,controller-id = <0>;
> +		nvidia,aspm-cmrt-us = <60>;
> +		nvidia,aspm-pwr-on-t-us = <20>;
> +		nvidia,aspm-l0s-entrance-latency-us = <3>;
> +
> +		bus-range = <0x0 0xff>;
> +		ranges = <0x81000000 0x0 0x38100000 0x0 0x38100000 0x0 0x00100000      /* downstream I/O (1MB) */
> +			  0x82000000 0x0 0x38200000 0x0 0x38200000 0x0 0x01E00000      /* non-prefetchable memory (30MB) */
> +			  0xc2000000 0x18 0x00000000 0x18 0x00000000 0x4 0x00000000>;  /* prefetchable memory (16GB) */
> +	};
> +
> +Board DTS:

Just make the example a single node. This split is convention, but not 
part of the binding definition.

> +
> +	pcie@14180000 {
> +		status = "okay";
> +
> +		vddio-pex-ctl-supply = <&vdd_1v8ao>;
> +
> +		phys = <&p2u_hsio_2>, <&p2u_hsio_3>, <&p2u_hsio_4>,
> +		       <&p2u_hsio_5>;
> +		phy-names = "p2u-0", "p2u-1", "p2u-2", "p2u-3";
> +	};
> -- 
> 2.17.1
>