| Message ID | 20231109191355.27738-2-james.quinlan@broadcom.com |
|---|---|
| State | New |
| Headers | show |
| Series | PCI: brcmstb: Configure appropriate HW CLKREQ# mode | expand |
On Thu, Nov 09, 2023 at 02:13:52PM -0500, Jim Quinlan wrote: > 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@broadcom.com> > --- > .../bindings/pci/brcm,stb-pcie.yaml | 21 +++++++++++++++++++ > 1 file changed, 21 insertions(+) > > diff --git a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml > index 7e15aae7d69e..992b35e915a5 100644 > --- a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml > +++ b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml > @@ -64,6 +64,27 @@ properties: > > aspm-no-l0s: true > > + brcm,clkreq-mode: > + description: A string that determines the operating > + clkreq mode of the PCIe RC HW WRT controlling the refclk signal. I assume "WRT" is shorthand for "with respect to", but it's slightly confusing following all the other acronyms. > + 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 Tclron max > + timing of 400ns as specified in "Dynamic Clock Control", > + section 3.2.5.2.2 of the PCIe spec. This situation is > + atypical and should happen only with older devices. These are all weirdly wrapped. Really no reason to use lines shorter than 80. Same spec citation question as in patch 2/3. > + $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
diff --git a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml index 7e15aae7d69e..992b35e915a5 100644 --- a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml +++ b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml @@ -64,6 +64,27 @@ properties: aspm-no-l0s: true + brcm,clkreq-mode: + description: A string that determines the operating + clkreq mode of the PCIe RC HW WRT 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 Tclron max + timing of 400ns as specified in "Dynamic Clock Control", + section 3.2.5.2.2 of the PCIe spec. 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
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@broadcom.com> --- .../bindings/pci/brcm,stb-pcie.yaml | 21 +++++++++++++++++++ 1 file changed, 21 insertions(+)