https://lore.kernel.org/linux-pci/20171215201434.GY30595@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ On Wed, Jul 20, 2022 at 6:06 PM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > > On Sat, Jul 16, 2022 at 06:24:50PM -0400, Jim Quinlan wrote: > > Our PCIe RC HW has an atypical behavior: if it does not have PCIe link > > established between itself and downstream, any subsequent config space > > access causes a CPU abort. This commit sets a "refusal mode" if the PCIe > > link-up fails, and this has our pci_ops map_bus function returning a NULL > > address, which in turn precludes the access from happening. > > > > Right now, "refusal mode" is window dressing. It will become relevant > > in a future commit when brcm_pcie_start_link() is invoked during > > enumeration instead of before it. > > > > Signed-off-by: Jim Quinlan <jim2101024@xxxxxxxxx> > > --- > > drivers/pci/controller/pcie-brcmstb.c | 24 ++++++++++++++++++++++++ > > 1 file changed, 24 insertions(+) > > > > diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c > > index c026446d5830..72219a4f3964 100644 > > --- a/drivers/pci/controller/pcie-brcmstb.c > > +++ b/drivers/pci/controller/pcie-brcmstb.c > > @@ -255,6 +255,7 @@ struct brcm_pcie { > > u32 hw_rev; > > void (*perst_set)(struct brcm_pcie *pcie, u32 val); > > void (*bridge_sw_init_set)(struct brcm_pcie *pcie, u32 val); > > + bool refusal_mode; > > }; > > > > static inline bool is_bmips(const struct brcm_pcie *pcie) > > @@ -687,6 +688,19 @@ static void __iomem *brcm_pcie_map_conf(struct pci_bus *bus, unsigned int devfn, > > if (pci_is_root_bus(bus)) > > return PCI_SLOT(devfn) ? NULL : base + where; > > > > + if (pcie->refusal_mode) { > > + /* > > + * At this point we do not have PCIe link-up. If there is > > + * a config read or write access besides those targeting > > + * the host bridge, our PCIe HW throws a CPU abort. To > > + * prevent this we return the NULL address. The calling > > + * functions -- pci_generic_config_*() -- will notice this > > + * and not perform the access, and if it is a read access, > > + * 0xffffffff is returned. > > + */ > > + return NULL; > > + } > > Is this any different from all the other .map_bus() implementations > that return NULL when the link is down? Not really,,but long ago I submitted code that gated the config spec access based on link status and was advised not to do it [1]. I'll be happy to make it look like the others. Regards, Jim Quinlan Broadcom STB [1] https://lore.kernel.org/linux-pci/20171215201434.GY30595@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ > > cdns_pci_map_bus() > dw_pcie_other_conf_map_bus() > nwl_pcie_map_bus() (see nwl_pcie_valid_device()) > xilinx_pcie_map_bus() (see xilinx_pcie_valid_device()) > > If you can implement this the same way, i.e., using > brcm_pcie_link_up(), it would be nice. > > > /* For devices, write to the config space index register */ > > idx = PCIE_ECAM_OFFSET(bus->number, devfn, 0); > > writel(idx, pcie->base + PCIE_EXT_CFG_INDEX); > > @@ -704,6 +718,11 @@ static void __iomem *brcm_pcie_map_conf32(struct pci_bus *bus, unsigned int devf > > if (pci_is_root_bus(bus)) > > return PCI_SLOT(devfn) ? NULL : base + (where & ~0x3); > > > > + if (pcie->refusal_mode) { > > + /* See note above in brcm_pcie_map_conf() */ > > + return NULL; > > + } > > + > > /* For devices, write to the config space index register */ > > idx = PCIE_ECAM_OFFSET(bus->number, devfn, (where & ~3)); > > writel(idx, base + IDX_ADDR(pcie)); > > @@ -989,6 +1008,7 @@ static int brcm_pcie_start_link(struct brcm_pcie *pcie) > > dev_err(dev, "link down\n"); > > return -ENODEV; > > } > > + pcie->refusal_mode = false; > > > > if (!brcm_pcie_rc_mode(pcie)) { > > dev_err(dev, "PCIe misconfigured; is in EP mode\n"); > > @@ -1134,6 +1154,8 @@ static void brcm_pcie_turn_off(struct brcm_pcie *pcie) > > void __iomem *base = pcie->base; > > int tmp; > > > > + pcie->refusal_mode = true; > > + > > if (brcm_pcie_link_up(pcie)) > > brcm_pcie_enter_l23(pcie); > > /* Assert fundamental reset */ > > @@ -1185,6 +1207,7 @@ static int brcm_pcie_resume(struct device *dev) > > u32 tmp; > > int ret; > > > > + pcie->refusal_mode = true; > > base = pcie->base; > > ret = clk_prepare_enable(pcie->clk); > > if (ret) > > @@ -1361,6 +1384,7 @@ static int brcm_pcie_probe(struct platform_device *pdev) > > pcie->type = data->type; > > pcie->perst_set = data->perst_set; > > pcie->bridge_sw_init_set = data->bridge_sw_init_set; > > + pcie->refusal_mode = true; > > > > pcie->base = devm_platform_ioremap_resource(pdev, 0); > > if (IS_ERR(pcie->base)) > > -- > > 2.17.1 > > > > > > _______________________________________________ > > linux-arm-kernel mailing list > > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
Attachment:
smime.p7s
Description: S/MIME Cryptographic Signature
