PCI: tegra194: Fix CBB timeout caused by DBI access before core power-on

When PERST# is deasserted twice (assert -> deassert -> assert -> deassert),
a CBB (Control Backbone) timeout occurs at DBI register offset 0x8bc
(PCIE_MISC_CONTROL_1_OFF). This happens because pci_epc_deinit_notify()
and dw_pcie_ep_cleanup() are called before reset_control_deassert() powers
on the controller core.

The call chain that causes the timeout:

  pex_ep_event_pex_rst_deassert()
    pci_epc_deinit_notify()
      pci_epf_test_epc_deinit()
        pci_epf_test_clear_bar()
          pci_epc_clear_bar()
            dw_pcie_ep_clear_bar()
              __dw_pcie_ep_reset_bar()
                dw_pcie_dbi_ro_wr_en()      <- Accesses 0x8bc DBI register
    reset_control_deassert(pcie->core_rst)  <- Core powered on HERE

The DBI registers, including PCIE_MISC_CONTROL_1_OFF (0x8bc), are only
accessible after the controller core is powered on via
reset_control_deassert(pcie->core_rst). Accessing them before this point
results in a CBB timeout because the hardware is not yet operational.

Fix this by moving pci_epc_deinit_notify() and dw_pcie_ep_cleanup() to
after reset_control_deassert(pcie->core_rst), ensuring the controller is
fully powered on before any DBI register accesses occur.

Fixes: 40e2125381dc ("PCI: tegra194: Move controller cleanups to pex_ep_event_pex_rst_deassert()")
Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-by: Vidya Sagar <vidyas@nvidia.com>
Link: https://patch.msgid.link/20260324190755.1094879-15-mmaddireddy@nvidia.com

diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
index eb24f88e0175b2bbfb114ed84c925ec96403bcb3..336d3c759547ab223200bd89e0ec5b8fcdaff1cb 100644 (file)
--- a/drivers/pci/controller/dwc/pcie-tegra194.c
+++ b/drivers/pci/controller/dwc/pcie-tegra194.c
@@ -1750,10 +1750,6 @@ static void pex_ep_event_pex_rst_deassert(struct tegra_pcie_dw *pcie)
                goto fail_phy;
        }
 
-       /* Perform cleanup that requires refclk */
-       pci_epc_deinit_notify(pcie->pci.ep.epc);
-       dw_pcie_ep_cleanup(&pcie->pci.ep);
-
        /* Clear any stale interrupt statuses */
        appl_writel(pcie, 0xFFFFFFFF, APPL_INTR_STATUS_L0);
        appl_writel(pcie, 0xFFFFFFFF, APPL_INTR_STATUS_L1_0_0);
@@ -1823,6 +1819,10 @@ static void pex_ep_event_pex_rst_deassert(struct tegra_pcie_dw *pcie)
 
        reset_control_deassert(pcie->core_rst);
 
+       /* Perform cleanup that requires refclk and core reset deasserted */
+       pci_epc_deinit_notify(pcie->pci.ep.epc);
+       dw_pcie_ep_cleanup(&pcie->pci.ep);
+
        val = dw_pcie_readl_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL);
        val &= ~PORT_LOGIC_SPEED_CHANGE;
        dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, val);