[PATCH v4] PCI: Xilinx NWL: Modifying irq chip for legacy interrupts

 > On 03/02/17 12:16, Bharat Kumar Gogada wrote:

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On 03/02/17 11:08, Bharat Kumar Gogada wrote:

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- Adding mutex lock for protecting legacy mask register
- Few wifi end points which only support legacy interrupts, performs
hardware reset functionalities after disabling interrupts by
invoking disable_irq and then re-enable using enable_irq, they
enable hardware interrupts first and then virtual irq line later.
- The legacy irq line goes low only after DEASSERT_INTx is
received.As the legacy irq line is high immediately after hardware
interrupts are enabled but virq of EP is still in disabled state and
EP handler is never executed resulting no DEASSERT_INTx.If dummy irq
chip is used, interrutps are not masked and system is hanging with CPU stall.
- Adding irq chip functions instead of dummy irq chip for legacy
interrupts.
- Legacy interrupts are level sensitive, so using handle_level_irq
is more appropriate as it is masks interrupts until End point
handles interrupts and unmasks interrutps after End point handler is

executed.

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- Legacy interrupts are level triggered, virtual irq line of End
Point shows as edge in /proc/interrupts.
- Setting irq flags of virtual irq line of EP to level triggered at
the time of mapping.

Signed-off-by: Bharat Kumar Gogada <redacted>
---
 drivers/pci/host/pcie-xilinx-nwl.c |   45

+++++++++++++++++++++++++++++++++++-

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 1 files changed, 44 insertions(+), 1 deletions(-)

diff --git a/drivers/pci/host/pcie-xilinx-nwl.c

b/drivers/pci/host/pcie-xilinx-nwl.c
index 43eaa4a..e4605f9 100644

--- a/drivers/pci/host/pcie-xilinx-nwl.c
+++ b/drivers/pci/host/pcie-xilinx-nwl.c

@@ -184,6 +184,7 @@ struct nwl_pcie {
 	u8 root_busno;
 	struct nwl_msi msi;
 	struct irq_domain *legacy_irq_domain;
+	spinlock_t leg_mask_lock;
 };

 static inline u32 nwl_bridge_readl(struct nwl_pcie *pcie, u32 off)

@@
-395,11 +396,52 @@ static void nwl_pcie_msi_handler_low(struct
irq_desc

*desc)

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 	chained_irq_exit(chip, desc);
 }

+static void nwl_mask_leg_irq(struct irq_data *data) {
+	struct irq_desc *desc = irq_to_desc(data->irq);
+	struct nwl_pcie *pcie;
+	unsigned long flags;
+	u32 mask;
+	u32 val;
+
+	pcie = irq_desc_get_chip_data(desc);
+	mask = 1 << (data->hwirq - 1);
+	spin_lock_irqsave(&pcie->leg_mask_lock, flags);

I've asked you to use a raw spinlock for a reason. If using RT, this
gets turned into a sleeping lock...

 In include/linux/spinlock.h
#define spin_lock_irqsave(lock, flags)                          \
do {                                                            \
        raw_spin_lock_irqsave(spinlock_check(lock), flags);     \
} while (0)

The above API invokes raw_spin_lock_irqsave know.
So is there any difference between raw_spin_lock_irqsave and

spin_lock_irqsave ?

When using RT, yes. RT upgrades all spinlocks to sleeping locks. We're trying
hard not to break RT, despite most of it not being merged yet. So your patch will
work on mainline Linux, and will break horribly on Linux/RT.

So please, turn this into a raw spinlock as requested.

Thanks for the explanation, will do it. 

Regards,
Bharat