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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org It'd be nice to mention the property names (maybe omit the "brcm," prefix if that helps) in the commit log so "git log --oneline" is more useful: 959e000f0463 ("dt-bindings: PCI: brcmstb: Add two optional props") ea372f45cfff ("dt-bindings: PCI: Add bindings for Brcmstb EP voltage regulators") 504253e44a9d ("dt-bindings: PCI: Correct brcmstb interrupts, interrupt-map.") 145790e55d82 ("dt-bindings: PCI: Add compatible string for Brcmstb 74[23]5 MIPs SOCs") 5e8a7d26d935 ("dt-bindings: PCI: brcmstb: compatible is required") f435ce7ebf8c ("dt-bindings: PCI: brcmstb: add BCM4908 binding") On Tue, Apr 11, 2023 at 12:59:16PM -0400, Jim Quinlan wrote: > Regarding "brcm,enable-l1ss": > > The Broadcom STB/CM PCIe HW -- a core that is also used by RPi SOCs -- > requires the driver probe() to deliberately place the HW one of three > CLKREQ# modes: > > (a) CLKREQ# driven by the RC unconditionally > (b) CLKREQ# driven by the EP for ASPM L0s, L1 > (c) Bidirectional CLKREQ#, as used for L1 Substates (L1SS). > > The HW+driver can tell the difference between downstream devices that > need (a) and (b), but does not know when to configure (c). Further, the > HW may cause a CPU abort on boot if guesses wrong regarding the need for > (c). So we introduce the boolean "brcm,enable-l1ss" property to indicate > that (c) is desired. Setting this property only makes sense when the > downstream device is L1SS-capable and the OS is configured to activate > this mode (e.g. policy==superpowersave). > > This property is already present in the Raspian version of Linux, but the > upstream driver implementaion that will follow adds more details and > discerns between (a) and (b). > > Regarding "brcm,completion-timeout-us" > > Our HW will cause a CPU abort if the L1SS exit time is longer than the > PCIe transaction completion abort timeout. We've been asked to make this > configurable, so we are introducing "brcm,completion-timeout-us". Completion Timeout is a generic PCIe concept. Do we want a generic (non-brcm) name that would be documented elsewhere? Rob? > Signed-off-by: Jim Quinlan > --- > .../devicetree/bindings/pci/brcm,stb-pcie.yaml | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > diff --git a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml > index 7e15aae7d69e..f7fc2f6561bb 100644 > --- a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml > +++ b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml > @@ -64,6 +64,22 @@ properties: > > aspm-no-l0s: true > > + brcm,enable-l1ss: > + description: Indicates that PCIe L1SS power savings > + are desired, the downstream device is L1SS-capable, and the > + OS has been configured to enable this mode. Note that when > + in this mode, this particular HW may not meet the requirement > + that requires CLKREQ# assertion to clock active to be > + within 400ns. Maybe a pointer to the source of the 400ns requirement? "requirement that requires" is a little redundant, maybe "... may not meet the requirement that Refclk be valid within 400ns of CLKREQ# assertion"? (I don't actually know whether this refers to Refclk or if that would be a true statement; this is just a possible sentence structure.) _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel