[PATCH 1/4] PCI: imx6: Mark the msi cascade handler IRQF_NO_THREAD

[Kevin Hao <haokexin@gmail.com>]

The cascade handler must run in hard interrupt context, otherwise
it will cause the following kernel warning if we force threading
of all the interrupt handlers via kernel command parameter
"threadirqs":
   [ INFO: inconsistent lock state ]
   4.2.0-rc3-next-20150723 #28 Not tainted
   ---------------------------------
   inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
   irq/21-mx6-pcie/62 [HC0[0]:SC0[2]:HE1:SE0] takes:
    (&irq_desc_lock_class){?.-...}, at: [<80078d94>] handle_simple_irq+0x1c/0xc0
   {IN-HARDIRQ-W} state was registered at:
     [<8006aa70>] lock_acquire+0x74/0x94
     [<807acc6c>] _raw_spin_lock+0x34/0x44
     [<8007900c>] handle_fasteoi_irq+0x20/0x1b8
     [<80075720>] generic_handle_irq+0x28/0x38
     [<80075864>] __handle_domain_irq+0x6c/0xe0
     [<80009558>] gic_handle_irq+0x28/0x68
     [<80013b64>] __irq_svc+0x44/0x5c
     [<807ad400>] _raw_spin_unlock_irq+0x30/0x34
     [<8004cffc>] finish_task_switch+0xc0/0x218
     [<807a7a10>] __schedule+0x248/0x6e0
     [<807a7fac>] schedule+0x38/0x9c
     [<807a8240>] schedule_preempt_disabled+0x10/0x14
     [<80063f8c>] cpu_startup_entry+0xfc/0x1f8
     [<8079f640>] rest_init+0x130/0x16c
     [<80a55ca4>] start_kernel+0x374/0x3e8
     [<1000807c>] 0x1000807c
   irq event stamp: 16
   hardirqs last  enabled at (15): [<807ad3fc>] _raw_spin_unlock_irq+0x2c/0x34
   hardirqs last disabled at (14): [<807acd80>] _raw_spin_lock_irq+0x20/0x58
   softirqs last  enabled at (0): [<800283d8>] copy_process.isra.58+0x3bc/0x1504
   softirqs last disabled at (16): [<80076f08>] irq_forced_thread_fn+0x0/0x68

   other info that might help us debug this:
    Possible unsafe locking scenario:

          CPU0
          ----
     lock(&irq_desc_lock_class);
     <Interrupt>
       lock(&irq_desc_lock_class);

    *** DEADLOCK ***

   no locks held by irq/21-mx6-pcie/62.

   stack backtrace:
   CPU: 0 PID: 62 Comm: irq/21-mx6-pcie Not tainted 4.2.0-rc3-next-20150723 #28
   Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
   Backtrace:
   [<80012dc4>] (dump_backtrace) from [<80012f64>] (show_stack+0x18/0x1c)
    r6:be3eeb78 r5:00000000 r4:00000000 r3:00000000
   [<80012f4c>] (show_stack) from [<807a4b50>] (dump_stack+0x80/0x9c)
   [<807a4ad0>] (dump_stack) from [<807a2efc>] (print_usage_bug+0x270/0x2e4)
    r5:be3ee780 r4:80c579ec
   [<807a2c8c>] (print_usage_bug) from [<8006874c>] (mark_lock+0x5b4/0x6e0)
    r10:80c579ec r9:800678e0 r8:be3ee780 r7:00000000 r6:80c579ec r5:be3eeb78
    r4:00000002
   [<80068198>] (mark_lock) from [<80068f70>] (__lock_acquire+0x6f8/0x1e20)
    r10:00000001 r9:be3eeb78 r8:be3ee780 r7:00000008 r6:000003f8 r5:be3ee780
    r4:00000000
   [<80068878>] (__lock_acquire) from [<8006aa70>] (lock_acquire+0x74/0x94)
    r10:00000001 r9:00000001 r8:00000000 r7:00000001 r6:00000001 r5:60030013
    r4:00000000
   [<8006a9fc>] (lock_acquire) from [<807acc6c>] (_raw_spin_lock+0x34/0x44)
    r6:0000012c r5:00000001 r4:be1f4d64
   [<807acc38>] (_raw_spin_lock) from [<80078d94>] (handle_simple_irq+0x1c/0xc0)
    r5:be1f4d64 r4:be1f4d00
   [<80078d78>] (handle_simple_irq) from [<80075720>] (generic_handle_irq+0x28/0x38)
    r5:be28ee20 r4:0000012c
   [<800756f8>] (generic_handle_irq) from [<80321914>] (dw_handle_msi_irq+0x68/0x90)
    r4:00000001 r3:00000002
   [<803218ac>] (dw_handle_msi_irq) from [<8032265c>] (imx6_pcie_msi_handler+0x14/0x18)
    r7:80076f08 r6:be39efc0 r5:be154000 r4:be39efc0
   [<80322648>] (imx6_pcie_msi_handler) from [<80076f38>] (irq_forced_thread_fn+0x30/0x68)
   [<80076f08>] (irq_forced_thread_fn) from [<80076cb4>] (irq_thread+0x14c/0x19c)
    r6:be39efc0 r5:be154000 r4:be39efe0 r3:00000004
   [<80076b68>] (irq_thread) from [<80047f80>] (kthread+0xdc/0xf8)
    r10:00000000 r9:00000000 r8:00000000 r7:80076b68 r6:be39efc0 r5:be3a1000
    r4:00000000
   [<80047ea4>] (kthread) from [<8000fa38>] (ret_from_fork+0x14/0x3c)
    r7:00000000 r6:00000000 r5:80047ea4 r4:be3a1000

Signed-off-by: Kevin Hao <haokexin@gmail.com>
---
 drivers/pci/host/pci-imx6.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
index 233a196c6e66..fd5eb2e34fc0 100644
--- a/drivers/pci/host/pci-imx6.c
+++ b/drivers/pci/host/pci-imx6.c
@@ -544,7 +544,8 @@ static int __init imx6_add_pcie_port(struct pcie_port *pp,
 
 		ret = devm_request_irq(&pdev->dev, pp->msi_irq,
 				       imx6_pcie_msi_handler,
-				       IRQF_SHARED, "mx6-pcie-msi", pp);
+				       IRQF_SHARED | IRQF_NO_THREAD,
+				       "mx6-pcie-msi", pp);
 		if (ret) {
 			dev_err(&pdev->dev, "failed to request MSI irq\n");
 			return -ENODEV;
-- 
2.1.0