Re: [PATCH v4 1/5] dt-bindings: phy: Add STM32MP25 COMBOPHY bindings
From: Christian Bruel
Date: Thu Aug 29 2024 - 07:08:22 EST
On 8/28/24 18:11, Conor Dooley wrote:
On Wed, Aug 28, 2024 at 04:34:48PM +0200, Christian Bruel wrote:
Document the bindings for STM32 COMBOPHY interface, used to support
the PCIe and USB3 stm32mp25 drivers.
Following entries can be used to tune caracterisation parameters
- st,output-micro-ohms and st,output-vswing-microvolt bindings entries
to tune the impedance and voltage swing using discrete simulation results
- st,rx-equalizer register to set the internal rx equalizer filter value.
Signed-off-by: Christian Bruel <christian.bruel@xxxxxxxxxxx>
---
.../bindings/phy/st,stm32mp25-combophy.yaml | 128 ++++++++++++++++++
1 file changed, 128 insertions(+)
create mode 100644 Documentation/devicetree/bindings/phy/st,stm32mp25-combophy.yaml
diff --git a/Documentation/devicetree/bindings/phy/st,stm32mp25-combophy.yaml b/Documentation/devicetree/bindings/phy/st,stm32mp25-combophy.yaml
new file mode 100644
index 000000000000..8d4a40b94507
--- /dev/null
+++ b/Documentation/devicetree/bindings/phy/st,stm32mp25-combophy.yaml
@@ -0,0 +1,128 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/phy/st,stm32mp25-combophy.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: STMicroelectronics STM32MP25 USB3/PCIe COMBOPHY
+
+maintainers:
+ - Christian Bruel <christian.bruel@xxxxxxxxxxx>
+
+description:
+ Single lane PHY shared (exclusive) between the USB3 and PCIe controllers.
+ Supports 5Gbit/s for USB3 and PCIe gen2 or 2.5Gbit/s for PCIe gen1.
+
+properties:
+ compatible:
+ const: st,stm32mp25-combophy
+
+ reg:
+ maxItems: 1
+
+ "#phy-cells":
+ const: 1
+
+ clocks:
+ minItems: 2
+ items:
+ - description: apb Bus clock mandatory to access registers.
+ - description: ker Internal RCC reference clock for USB3 or PCIe
+ - description: pad Optional on board clock input for PCIe only. Typically an
+ external 100Mhz oscillator wired on dedicated CLKIN pad. Used as reference
+ clock input instead of the ker
+
+ clock-names:
+ minItems: 2
+ items:
+ - const: apb
+ - const: ker
+ - const: pad
+
+ resets:
+ maxItems: 1
+
+ reset-names:
+ const: phy
+
+ power-domains:
+ maxItems: 1
+
+ wakeup-source: true
+
+ interrupts:
+ maxItems: 1
+ description: interrupt used for wakeup
+
+ access-controllers:
+ minItems: 1
+ maxItems: 2
Can you please describe the items here?
I can specialize the description: "Phandle to the rifsc firewall device to check access right."
otherwise described in access-controllers/access-controllers.yaml, see also bindings/bus/st,stm32mp25-rifsc.yaml
+ st,syscfg:
+ $ref: /schemas/types.yaml#/definitions/phandle
+ description: Phandle to the SYSCON entry required for configuring PCIe
+ or USB3.
Why is a phandle required for this lookup, rather than doing it by
compatible?
the phandle is used to select the sysconf SoC configuration register
depending on the PCIe/USB3 mode (selected by xlate function), so it's
not like a lookup here. This sysconf register is also used for other
settings such as the PLL, Reference clock selection, ...
+
+ st,ssc-on:
+ type: boolean
flag, not boolean, for presence based stuff. And in the driver,
s/of_property_read_bool/of_property_present/.
ok
+ description:
+ A boolean property whose presence indicates that the SSC for common clock
+ needs to be set.
And what, may I ask, does "SSC" mean? "Common clock" is also a bit of a
"linuxism", what does this actually do in the hardware block?
SSC for Spread Spectrum Clocking. It is an hardware setting for the 100Mhz PCIe reference common clock,
I will rephrase the description
+
+ st,rx-equalizer:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ minimum: 0
+ maximum: 7
+ default: 2
+ description:
+ A 3 bit value to tune the RX fixed equalizer setting for optimal eye compliance
+
+ st,output-micro-ohms:
+ minimum: 3999000
+ maximum: 6090000
+ default: 4968000
+ description:
+ A value property to tune the Single Ended Output Impedance, simulations results
+ at 25C for a VDDP=0.8V. The hardware accepts discrete values in this range.
+
+ st,output-vswing-microvolt:
+ minimum: 442000
+ maximum: 803000
+ default: 803000
+ description:
+ A value property in microvolt to tune the Single Ended Output Voltage Swing to change the
+ Vlo, Vhi for a VDDP = 0.8V. The hardware accepts discrete values in this range.
+
+required:
+ - "#phy-cells"
+ - compatible
+ - clocks
+ - clock-names
+ - reg
+ - resets
+ - reset-names
+ - st,syscfg
The order here should reflect the ordering in a node, so compatible and
reg first, rather than sorted alphanumerically.
ok
+
+additionalProperties: false
+
+examples:
+ - |
+ #include <dt-bindings/clock/st,stm32mp25-rcc.h>
+ #include <dt-bindings/interrupt-controller/arm-gic.h>
+ #include <dt-bindings/reset/st,stm32mp25-rcc.h>
+
+ combophy: phy@480c0000 {
You can drop the label here, it ain't used by anything.
ok
thanks,
Christian
Cheers,
Conor.
+ compatible = "st,stm32mp25-combophy";
+ reg = <0x480c0000 0x1000>;
+ #phy-cells = <1>;
+ clocks = <&rcc CK_BUS_USB3PCIEPHY>, <&rcc CK_KER_USB3PCIEPHY>;
+ clock-names = "apb", "ker";
+ resets = <&rcc USB3PCIEPHY_R>;
+ reset-names = "phy";
+ st,syscfg = <&syscfg>;
+ access-controllers = <&rifsc 67>;
+ power-domains = <&CLUSTER_PD>;
+ wakeup-source;
+ interrupts-extended = <&exti1 45 IRQ_TYPE_EDGE_FALLING>;
+ };
+...
--
2.34.1