External email: Use caution opening links or attachmentsWe noticed PCIe link-up issues with some endpoints. link-up at the physical
Hi Vidya, question about ancient history:
On Tue, Aug 13, 2019 at 05:06:27PM +0530, Vidya Sagar wrote:
Add support for Synopsys DesignWare core IP based PCIe host controllerThis comment suggests that there's an issue with *Endpoints*, not an
present in Tegra194 SoC.
...
+static int tegra_pcie_dw_host_init(struct pcie_port *pp)
+{
+ struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+ struct tegra_pcie_dw *pcie = to_tegra_pcie(pci);
+ u32 val, tmp, offset, speed;
+
+ tegra_pcie_prepare_host(pp);
+
+ if (dw_pcie_wait_for_link(pci)) {
+ /*
+ * There are some endpoints which can't get the link up if
+ * root port has Data Link Feature (DLF) enabled.
+ * Refer Spec rev 4.0 ver 1.0 sec 3.4.2 & 7.7.4 for more info
+ * on Scaled Flow Control and DLF.
+ * So, need to confirm that is indeed the case here and attempt
+ * link up once again with DLF disabled.
issue with the Root Port. If so, it seems like this problem could
occur with all Root Ports, not just Tegra194. Do you remember any
details about this?
I don't remember hearing about any similar issues, and this driver is
the only place PCI_EXT_CAP_ID_DLF is referenced, so maybe it is
actually something related to Tegra194?
+ val = appl_readl(pcie, APPL_DEBUG);
+ val &= APPL_DEBUG_LTSSM_STATE_MASK;
+ val >>= APPL_DEBUG_LTSSM_STATE_SHIFT;
+ tmp = appl_readl(pcie, APPL_LINK_STATUS);
+ tmp &= APPL_LINK_STATUS_RDLH_LINK_UP;
+ if (!(val == 0x11 && !tmp)) {
+ /* Link is down for all good reasons */
+ return 0;
+ }
+
+ dev_info(pci->dev, "Link is down in DLL");
+ dev_info(pci->dev, "Trying again with DLFE disabled\n");
+ /* Disable LTSSM */
+ val = appl_readl(pcie, APPL_CTRL);
+ val &= ~APPL_CTRL_LTSSM_EN;
+ appl_writel(pcie, val, APPL_CTRL);
+
+ reset_control_assert(pcie->core_rst);
+ reset_control_deassert(pcie->core_rst);
+
+ offset = dw_pcie_find_ext_capability(pci, PCI_EXT_CAP_ID_DLF);
+ val = dw_pcie_readl_dbi(pci, offset + PCI_DLF_CAP);
+ val &= ~PCI_DLF_EXCHANGE_ENABLE;
+ dw_pcie_writel_dbi(pci, offset, val);
+
+ tegra_pcie_prepare_host(pp);
+
+ if (dw_pcie_wait_for_link(pci))
+ return 0;
+ }
+
+ speed = dw_pcie_readw_dbi(pci, pcie->pcie_cap_base + PCI_EXP_LNKSTA) &
+ PCI_EXP_LNKSTA_CLS;
+ clk_set_rate(pcie->core_clk, pcie_gen_freq[speed - 1]);
+
+ tegra_pcie_enable_interrupts(pp);
+
+ return 0;
+}