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

From: Vidya Sagar
Date: Tue May 07 2019 - 05:21:47 EST

On 4/26/2019 9:13 PM, Rob Herring wrote:
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@xxxxxxxxxx>
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
+ 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.
BPMP needs to know the controller number to enable it hence it needs to be
passed to BPMP. Just for accessing BPMP, I already added 'nvidia,bpmp' property.

+- 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

+- 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.
This is added mostly for debugging purposes where link is brought up at a lower speed (ex:- Gen-1)
and then by means of SW initiated speed change, it is taken to a higher speed.
I'll remove it from the next patch as I'm not sure if it deserves to go as a common entry.

+- 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?
Well, they are related partially. i.e. if a platform doesn't have 'supports-clkreq' set,
then, by definition, it can't advertise support for ASPM L1.1 and L1.2 states. But, ASPM-L0s
and ASPM-L1 states don't depend on 'supports-clkreq' property.
Having this property gives more granularity as to support for which particular ASPM state
shouldn't be advertised by the root port.

I think this should be common property. We already have a Rockchip
property to disable L0s.
I'm afraid it can't be a common property as not all implementations allow programming capabilty
registers before PCIe link up (as capability registers in a root port's configurations space are
otherwise read-only registers). Since this is more like a feature of Tegra194's PCIe root port,
I added it here.

Also, just use 0x1, 0x2, 0x4 instead of "bit-N to '1'"
Ok. I'll change this.

+- 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:

I'd drop this until this is solved in a common way.
I'm fine with it. I'll drop this for now and push patches to support WAKE at a
later point of time.

+ 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
+ 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";
+ };