The Broadcom STB/CM PCIe HW -- a core that is also used by RPi SOCs --
requires the driver to deliberately place the RC HW one of three CLKREQ#
modes. The "brcm,clkreq-mode" property allows the user to override the
default setting. If this property is omitted, the default mode shall be
"default".
Signed-off-by: Jim Quinlan <james.quinlan@xxxxxxxxxxxx>
---
.../devicetree/bindings/pci/brcm,stb-pcie.yaml | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml
index 7e15aae7d69e..22491f7f8852 100644
--- a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml
+++ b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml
@@ -64,6 +64,24 @@ properties:
aspm-no-l0s: true
+ brcm,clkreq-mode:
+ description: A string that determines the operating
+ clkreq mode of the PCIe RC HW with respect to controlling the refclk
+ signal. There are three different modes -- "safe", which drives the
+ refclk signal unconditionally and will work for all devices but does
+ not provide any power savings; "no-l1ss" -- which provides Clock
+ Power Management, L0s, and L1, but cannot provide L1 substate (L1SS)
+ power savings. If the downstream device connected to the RC is L1SS
+ capable AND the OS enables L1SS, all PCIe traffic may abruptly halt,
+ potentially hanging the system; "default" -- which provides L0s, L1,
+ and L1SS, but not compliant to provide Clock Power Management;
+ specifically, may not be able to meet the T_CLRon max timing of 400ns
+ as specified in "Dynamic Clock Control", section 3.2.5.2.2 PCI
+ Express Mini CEM 2.1 specification. This situation is atypical and
+ should happen only with older devices.
+ $ref: /schemas/types.yaml#/definitions/string
+ enum: [ safe, no-l1ss, default ]
+
brcm,scb-sizes:
description: u64 giving the 64bit PCIe memory
viewport size of a memory controller. There may be up to
--
2.17.1
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