On Mon, Aug 21, 2023 at 12:01:50PM -0400, Jim Quinlan wrote: > On Mon, Aug 21, 2023 at 11:41 AM Lorenzo Pieralisi > <lpieralisi@xxxxxxxxxx> wrote: > > > > On Mon, Aug 21, 2023 at 11:25:11AM -0400, Jim Quinlan wrote: > > > On Mon, Aug 21, 2023 at 10:47 AM Lorenzo Pieralisi > > > <lpieralisi@xxxxxxxxxx> wrote: > > > > > > > > On Fri, Jun 23, 2023 at 10:40:54AM -0400, Jim Quinlan wrote: > > > > > This commit adds the boolean "brcm,enable-l1ss" property: > > > > > > > > > > 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). All devices > > > > > should work fine when the driver chooses (a) or (b), but (c) may be > > > > > desired to realize the extra power savings that L1SS offers. So we > > > > > introduce the boolean "brcm,enable-l1ss" property to inform the driver > > > > > 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==powersupersave). > > > > > > > > > > This property is already present in the Raspian version of Linux, but the > > > > > upstream driver implementation that follows adds more details and > > > > > discerns between (a) and (b). > > > > > > > > > > Signed-off-by: Jim Quinlan <james.quinlan@xxxxxxxxxxxx> > > > > > Reviewed-by: Rob Herring <robh@xxxxxxxxxx> > > > > > --- > > > > > Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml | 9 +++++++++ > > > > > 1 file changed, 9 insertions(+) > > > > > > > > > > diff --git a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml > > > > > index 7e15aae7d69e..8b61c2179608 100644 > > > > > --- a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml > > > > > +++ b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml > > > > > @@ -64,6 +64,15 @@ 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. For boards > > > > > > > > What does this mean ? I don't think DT properties are supposed > > > > to carry information related to how the OS is configured. > > > > > > The DT setting in question is unrelated to the statement "and the OS > > > has been configured to > > > enable this mode". > > > > > > This is merely saying that even if you enable "brcm,l1ss-enable" > > > that you may not get L1SS power savings w/o setting > > > "CONFIG_PCIEASPM_POWER_SUPERSAVE=y". > > > I mentioned that exact term but a reviewer nakked it because > > > apparently DT descriptions should not be OS specific. > > > > > > I am actually open for this to be a command-line option but I wanted to honor > > > what the Raspian OS folks have already done. RaspianOS already has > > > "brcm,enable-l1ss" > > > set in their DTS files. > > > > This is about the mainline kernel, I don't have any visibility into > > downstream kernels (where that property management was added without DT > > and PCI maintainers supervision). > > > > Raspian OS folks' choice is theirs but it can't and it shouldn't override > > the mainline review process even though I understand the position you > > are in. > > Understood, but using the command line has its warts as well; I now recall the > discussion Bjorn and I had regarding this option. I'm pretty sure > that upstreaam will not allow the following > possible command line kernel params: > > brcm,enable-l1ss > pci=brcm,entable-l1ss > > Bjorn suggested using the documented but (IMO) obscure and rarely > used format > > pci=[<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*pci:<vendor>:<device>[:<subvendor>:<subdevice>] > > but this is just going in the wrong direction; here's why. Using the > above iformat s completely dependent on the > PCI "linux-domaiin" property, a non-HW related DT property I might > add. Since "linux-domain" is already > a valid and well-used DT property, and the value of the above > command line format is dependent > on the value of the "linux-domain", why not be consistent and let > "brcm,enable-l1ss" be a Broadcom specific property? I am just asking to add a module_param to the host controller driver. Anyway - time is running out for v6.6, I need Rob's feedback, if I don't hear from him today I will merge the last three patches and postpone the discussion. Thanks, Lorenzo > > Regards, > Jim Quinlan > Broadcom STB/CM > > > > > > Thanks, > > Lorenzo > > > > > > > > Regards, > > > Jim > > > > > > > Again - it depends on what DT should be used for, I am not claiming to > > > > have any authority on that, just asking. > > > > > > > > Thanks, > > > > Lorenzo > > > > > > > > > + using a mini-card connector, this mode may not meet the > > > > > + TCRLon maximum time of 400ns, as specified in 3.2.5.2.2 > > > > > + of the PCI Express Mini CEM 2.0 specification. > > > > > + type: boolean > > > > > + > > > > > brcm,scb-sizes: > > > > > description: u64 giving the 64bit PCIe memory > > > > > viewport size of a memory controller. There may be up to > > > > > -- > > > > > 2.17.1 > > > > > > > > > > > > > > > > >
