MIPS: DECstation I/O ASIC DMA interrupt handling fix

Maciej W. Rozycki · ralfbaechle · commit 5359b938c088 · 2013-09-13T11:57:40.000+02:00
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 <macro@linux-mips.org> Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/5826/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/dec/ioasic-irq.c b/arch/mips/dec/ioasic-irq.c
@@ -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,
diff --git a/arch/mips/include/asm/dec/ioasic.h b/arch/mips/include/asm/dec/ioasic.h
@@ -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);
diff --git a/drivers/net/ethernet/amd/declance.c b/drivers/net/ethernet/amd/declance.c
@@ -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;
 }

Original file line number	Diff line number	Diff line change
`@@ -31,6 +31,8 @@ static inline u32 ioasic_read(unsigned int reg)`
`31`	`31`	`return ioasic_base[reg / 4];`
`32`	`32`	`}`
`33`	`33`
	`34`	`+extern void clear_ioasic_dma_irq(unsigned int irq);`
	`35`	`+`
`34`	`36`	`extern void init_ioasic_irqs(int base);`
`35`	`37`
`36`	`38`	`extern int dec_ioasic_clocksource_init(void);`
Original file line number	Diff line number	Diff line change
`@@ -725,6 +725,7 @@ static irqreturn_t lance_dma_merr_int(int irq, void *dev_id)`
`725`	`725`	`{`
`726`	`726`	`struct net_device *dev = dev_id;`
`727`	`727`
	`728`	`+ clear_ioasic_dma_irq(irq);`
`728`	`729`	`printk(KERN_ERR "%s: DMA error\n", dev->name);`
`729`	`730`	`return IRQ_HANDLED;`
`730`	`731`	`}`