Re: [PATCH 1/4] PCI: dwc: Advertise L1 PM Substates only if driver requests it

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, Nov 12, 2025 at 11:21:07PM +0530, Manivannan Sadhasivam wrote:
> On Wed, Nov 12, 2025 at 09:22:36AM +0100, Niklas Cassel wrote:
> > On Tue, Nov 11, 2025 at 04:16:08PM -0600, Bjorn Helgaas wrote:
> > > --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> > > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> > > @@ -1060,6 +1060,8 @@ int dw_pcie_setup_rc(struct dw_pcie_rp *pp)
> > >  		PCI_COMMAND_MASTER | PCI_COMMAND_SERR;
> > >  	dw_pcie_writel_dbi(pci, PCI_COMMAND, val);
> > >  
> > > +	dw_pcie_config_l1ss(pci);

> > > --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > > +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > > @@ -1067,6 +1067,8 @@ static int qcom_pcie_init_2_7_0(struct qcom_pcie *pcie)
> > >  	val &= ~REQ_NOT_ENTR_L1;
> > >  	writel(val, pcie->parf + PARF_PM_CTRL);
> > >  
> > > +	pci->l1ss_support = true;
> > > +
> > >  	val = readl(pcie->parf + PARF_AXI_MSTR_WR_ADDR_HALT_V2);
> > >  	val |= EN;
> > >  	writel(val, pcie->parf + PARF_AXI_MSTR_WR_ADDR_HALT_V2);
> > 
> > While it seems like ops_2_7_0 is the only type that explicitly does a
> > register write to enable L1ss, other versions might have the register
> > as enabled by default, so it would be nice if Mani could confirm exactly
> > which versions that should set l1ss_support = true.
> > 
> 
> Yes, on the rest of the platforms, this bit is supposed to be enabled by
> default. AFAIK, all Qcom platforms should support L1SS, atleast the
> non-IPQ/APQ ones.
> 
> We should set it for below cfgs:
> 
> cfg_fw_managed
> cfg_sc8280xp
> cfg_1_34_0
> cfg_1_9_0
> cfg_2_7_0

Except for cfg_fw_managed, the above are all covered by
qcom_pcie_init_2_7_0(), either via ops_2_7_0, ops_1_9_0, or
ops_1_21_0.

cfg_fw_managed is harder because we don't use dw_pcie_host_init() or
dw_pcie_setup_rc().

We do allocate a struct dw_pcie (where l1ss_support is) in
qcom_pcie_ecam_host_init(), but only so we can call
dw_pcie_msi_host_init() and dw_pcie_msi_init().

Neither of those seems like a logical place to fiddle with L1SS
support.

Open to suggestions.

Bjorn