On Thu, Apr 30, 2020 at 02:55:22PM -0400, Jim Quinlan wrote: > From: Jim Quinlan <[email protected]> > > Some informal internal experiments has shown that the BrcmSTB ASPM L0s > savings may introduce an undesirable noise signal on some customers' > boards. In addition, L0s was found lacking in realized power savings, > especially relative to the L1 ASPM component. This is BrcmSTB's > experience and may not hold for others. At any rate, we disable L0s > savings by default unless the DT node has the 'brcm,aspm-en-l0s' > property.
I assume this works by writing the PCIe Link Capabilities register, which is read-only via the config space path used by the generic ASPM code, so that code thinks the device doesn't support L0s at all. Documentation/devicetree/bindings/pci/rockchip-pcie-host.txt includes an "aspm-no-l0s" property. It'd be nice if this could use the same property. > Signed-off-by: Jim Quinlan <[email protected]> > --- > drivers/pci/controller/pcie-brcmstb.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/controller/pcie-brcmstb.c > b/drivers/pci/controller/pcie-brcmstb.c > index 2bc913c0262c..bc1d514b19e4 100644 > --- a/drivers/pci/controller/pcie-brcmstb.c > +++ b/drivers/pci/controller/pcie-brcmstb.c > @@ -44,6 +44,9 @@ > #define PCIE_RC_CFG_PRIV1_ID_VAL3 0x043c > #define PCIE_RC_CFG_PRIV1_ID_VAL3_CLASS_CODE_MASK 0xffffff > > +#define PCIE_RC_CFG_PRIV1_LINK_CAPABILITY 0x04dc > +#define PCIE_RC_CFG_PRIV1_LINK_CAPABILITY_ASPM_SUPPORT_MASK 0xc00 > + > #define PCIE_RC_DL_MDIO_ADDR 0x1100 > #define PCIE_RC_DL_MDIO_WR_DATA 0x1104 > #define PCIE_RC_DL_MDIO_RD_DATA 0x1108 > @@ -696,7 +699,7 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie) > int num_out_wins = 0; > u16 nlw, cls, lnksta; > int i, ret; > - u32 tmp; > + u32 tmp, aspm_support; > > /* Reset the bridge */ > brcm_pcie_bridge_sw_init_set(pcie, 1); > @@ -806,6 +809,15 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie) > num_out_wins++; > } > > + /* Only support ASPM L1 unless L0s is explicitly desired */ > + aspm_support = PCIE_LINK_STATE_L1; > + if (of_property_read_bool(pcie->np, "brcm,aspm-en-l0s")) > + aspm_support |= PCIE_LINK_STATE_L0S; > + tmp = readl(base + PCIE_RC_CFG_PRIV1_LINK_CAPABILITY); > + u32p_replace_bits(&tmp, aspm_support, > + PCIE_RC_CFG_PRIV1_LINK_CAPABILITY_ASPM_SUPPORT_MASK); > + writel(tmp, base + PCIE_RC_CFG_PRIV1_LINK_CAPABILITY); > + > /* > * For config space accesses on the RC, show the right class for > * a PCIe-PCIe bridge (the default setting is to be EP mode). > -- > 2.17.1 >
