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MIPS: DECstation I/O ASIC DMA interrupt handling fix
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This change complements commit d0da7c0
and brings clear_ioasic_irq back, renaming it to clear_ioasic_dma_irq at
the same time, to make I/O ASIC DMA interrupts functional.

Unlike ordinary I/O ASIC interrupts DMA interrupts need to be deasserted
by software by writing 0 to the respective bit in I/O ASIC's System
Interrupt Register (SIR), similarly to how CP0.Cause.IP0 and CP0.Cause.IP1
bits are handled in the CPU (the difference is SIR DMA interrupt bits are
R/W0C so there's no need for an RMW cycle).  Otherwise the handler is
reentered over and over again.

The only current user is the DEC LANCE Ethernet driver and its extremely
uncommon DMA memory error handler that does not care when exactly the
interrupt is cleared.  Anticipating the use of DMA interrupts by the Zilog
SCC driver this change however exports clear_ioasic_dma_irq for device
drivers to choose the right application-specific sequence to clear the
request explicitly rather than calling it implicitly in the .irq_eoi
handler of `struct irq_chip'.  Previously these interrupts were cleared in
the .end handler of the said structure, before it was removed.

Signed-off-by: Maciej W. Rozycki <[email protected]>
Cc: [email protected]
Patchwork: https://patchwork.linux-mips.org/patch/5826/
Signed-off-by: Ralf Baechle <[email protected]>
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Maciej W. Rozycki authored and ralfbaechle committed Sep 13, 2013
1 parent daed128 commit 5359b93
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Showing 3 changed files with 11 additions and 0 deletions.
8 changes: 8 additions & 0 deletions arch/mips/dec/ioasic-irq.c
Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,14 @@ static struct irq_chip ioasic_irq_type = {
.irq_unmask = unmask_ioasic_irq,
};

void clear_ioasic_dma_irq(unsigned int irq)
{
u32 sir;

sir = ~(1 << (irq - ioasic_irq_base));
ioasic_write(IO_REG_SIR, sir);
}

static struct irq_chip ioasic_dma_irq_type = {
.name = "IO-ASIC-DMA",
.irq_ack = ack_ioasic_irq,
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2 changes: 2 additions & 0 deletions arch/mips/include/asm/dec/ioasic.h
Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,8 @@ static inline u32 ioasic_read(unsigned int reg)
return ioasic_base[reg / 4];
}

extern void clear_ioasic_dma_irq(unsigned int irq);

extern void init_ioasic_irqs(int base);

extern int dec_ioasic_clocksource_init(void);
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1 change: 1 addition & 0 deletions drivers/net/ethernet/amd/declance.c
Original file line number Diff line number Diff line change
Expand Up @@ -725,6 +725,7 @@ static irqreturn_t lance_dma_merr_int(int irq, void *dev_id)
{
struct net_device *dev = dev_id;

clear_ioasic_dma_irq(irq);
printk(KERN_ERR "%s: DMA error\n", dev->name);
return IRQ_HANDLED;
}
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