PCI: tegra: Mask AFI_INTR in runtime suspend [Linux 5.3]

This Linux kernel change "PCI: tegra: Mask AFI_INTR in runtime suspend" is included in the Linux 5.3 release. This change is authored by Manikanta Maddireddy <mmaddireddy [at] nvidia.com> on Tue Jun 18 23:31:43 2019 +0530. The commit for this change in Linux stable tree is 316b9ef (patch).

PCI: tegra: Mask AFI_INTR in runtime suspend

AFI_INTR is unmasked in tegra_pcie_enable_controller(), mask it to avoid
unwanted interrupts raised by AFI after pex_rst is asserted.

The following sequence triggers such scenario:

- tegra_pcie_remove() triggers runtime suspend
- pex_rst is asserted in runtime suspend
- PRSNT_MAP bit field in RP_PRIV_MISC register changes from EP_PRSNT to
  EP_ABSNT
- This is sensed by AFI and triggers "Slot present pin change" interrupt
- tegra_pcie_isr() function accesses AFI register when runtime suspend
  is going through power off sequence

Resulting faulty backtrace:

rmmod pci-tegra
 pci_generic_config_write32: 108 callbacks suppressed
 pci_bus 0002:00: 2-byte config write to 0002:00:02.0 offset 0x4c may corrupt adjacent RW1C bits
 pci_bus 0002:00: 2-byte config write to 0002:00:02.0 offset 0x9c may corrupt adjacent RW1C bits
 pci_bus 0002:00: 2-byte config write to 0002:00:02.0 offset 0x88 may corrupt adjacent RW1C bits
 pci_bus 0002:00: 2-byte config write to 0002:00:02.0 offset 0x90 may corrupt adjacent RW1C bits
 pci_bus 0002:00: 2-byte config write to 0002:00:02.0 offset 0x4 may corrupt adjacent RW1C bits
 igb 0002:04:00.1: removed PHC on enP2p4s0f1
 igb 0002:04:00.0: removed PHC on enP2p4s0f0
 pci_bus 0002:00: 2-byte config write to 0002:00:01.0 offset 0x4c may corrupt adjacent RW1C bits
 pci_bus 0002:00: 2-byte config write to 0002:00:01.0 offset 0x9c may corrupt adjacent RW1C bits
 pci_bus 0002:00: 2-byte config write to 0002:00:01.0 offset 0x88 may corrupt adjacent RW1C bits
 pci_bus 0002:00: 2-byte config write to 0002:00:01.0 offset 0x90 may corrupt adjacent RW1C bits
 pci_bus 0002:00: 2-byte config write to 0002:00:01.0 offset 0x4 may corrupt adjacent RW1C bits
 rcu: INFO: rcu_preempt self-detected stall on CPU
 SError Interrupt on CPU0, code 0xbf000002 -- SError
 CPU: 0 PID: 0 Comm: swapper/0 Tainted: G        W         5.1.0-rc3-next-20190405-00027-gcd8110499e6f-dirty #42
 Hardware name: NVIDIA Jetson TX1 Developer Kit (DT)
 pstate: 20000085 (nzCv daIf -PAN -UAO)
 pc : tegra_pcie_isr+0x58/0x178 [pci_tegra]
 lr : tegra_pcie_isr+0x40/0x178 [pci_tegra]
 sp : ffff000010003da0
 x29: ffff000010003da0 x28: 0000000000000000
 x27: ffff8000f9e61000 x26: ffff000010fbf420
 x25: ffff000011427f93 x24: ffff8000fa600410
 x23: ffff00001129d000 x22: ffff00001129d000
 x21: ffff8000f18bf3c0 x20: 0000000000000070
 x19: 00000000ffffffff x18: 0000000000000000
 x17: 0000000000000000 x16: 0000000000000000
 x15: 0000000000000000 x14: ffff000008d40a48
 x13: ffff000008d40a30 x12: ffff000008d40a20
 x11: ffff000008d40a10 x10: ffff000008d40a00
 x9 : ffff000008d409e8 x8 : ffff000008d40ae8
 x7 : ffff000008d40ad0 x6 : ffff000010003e58
 x5 : ffff8000fac00248 x4 : 0000000000000000
 x3 : ffff000008d40b08 x2 : fffffffffffffff8
 x1 : ffff000008d3f4e8 x0 : 00000000ffffffff
 Kernel panic - not syncing: Asynchronous SError Interrupt
 CPU: 0 PID: 0 Comm: swapper/0 Tainted: G        W         5.1.0-rc3-next-20190405-00027-gcd8110499e6f-dirty #42
 Hardware name: NVIDIA Jetson TX1 Developer Kit (DT)
 Call trace:
  dump_backtrace+0x0/0x158
  show_stack+0x14/0x20
  dump_stack+0xa8/0xcc
  panic+0x140/0x2f4
  nmi_panic+0x6c/0x70
  arm64_serror_panic+0x74/0x80
  __pte_error+0x0/0x28
  el1_error+0x84/0xf8
  tegra_pcie_isr+0x58/0x178 [pci_tegra]
  __handle_irq_event_percpu+0x70/0x198
  handle_irq_event_percpu+0x34/0x88
  handle_irq_event+0x48/0x78
  handle_fasteoi_irq+0xb4/0x190
  generic_handle_irq+0x24/0x38
  __handle_domain_irq+0x5c/0xb8
  gic_handle_irq+0x58/0xa8
  el1_irq+0xb8/0x180
  cpuidle_enter_state+0x138/0x358
  cpuidle_enter+0x18/0x20
  call_cpuidle+0x1c/0x48
  do_idle+0x230/0x2d0
  cpu_startup_entry+0x20/0x28
  rest_init+0xd4/0xe0
  arch_call_rest_init+0xc/0x14
  start_kernel+0x444/0x470

AFI_INTR is re-enabled on resume in tegra_pcie_pm_resume() through
tegra_pcie_enable_controller().

Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
[lorenzo.pieralisi@arm.com: updated log]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Thierry Reding <treding@nvidia.com>

There are 15 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/pci/controller/pci-tegra.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/pci/controller/pci-tegra.c b/drivers/pci/controller/pci-tegra.c
index 5d93bb3..b823a63 100644
--- a/drivers/pci/controller/pci-tegra.c
+++ b/drivers/pci/controller/pci-tegra.c
@@ -1641,6 +1641,15 @@ static int tegra_pcie_disable_msi(struct tegra_pcie *pcie)
    return 0;
 }

+static void tegra_pcie_disable_interrupts(struct tegra_pcie *pcie)
+{
+   u32 value;
+
+   value = afi_readl(pcie, AFI_INTR_MASK);
+   value &= ~AFI_INTR_MASK_INT_MASK;
+   afi_writel(pcie, value, AFI_INTR_MASK);
+}
+
 static int tegra_pcie_get_xbar_config(struct tegra_pcie *pcie, u32 lanes,
                      u32 *xbar)
 {
@@ -2486,6 +2495,12 @@ static int __maybe_unused tegra_pcie_pm_suspend(struct device *dev)

    tegra_pcie_disable_ports(pcie);

+   /*
+    * AFI_INTR is unmasked in tegra_pcie_enable_controller(), mask it to
+    * avoid unwanted interrupts raised by AFI after pex_rst is asserted.
+    */
+   tegra_pcie_disable_interrupts(pcie);
+
    if (pcie->soc->program_uphy) {
        err = tegra_pcie_phy_power_off(pcie);
        if (err < 0)

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