MIPS: ath79: rework IP2/IP3 interrupt handling

The current implementation assumes that flushing the
DDR writeback buffer is required for IP2/IP3 interrupts,
however this is not true for all SoCs.

Use SoC specific IP2/IP3 handlers instead of flushing
the buffers in the dispatcher code.
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Acked-by: Luis R. Rodriguez <mcgrof@qca.qualcomm.com>
Cc: linux-mips@linux-mips.org
Cc: mcgrof@infradead.org
Patchwork: https://patchwork.linux-mips.org/patch/3509/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/ath79/irq.c

 /*
  *  Atheros AR71xx/AR724x/AR913x specific interrupt handling
  *
- *  Copyright (C) 2008-2010 Gabor Juhos <juhosg@openwrt.org>
+ *  Copyright (C) 2008-2011 Gabor Juhos <juhosg@openwrt.org>
  *  Copyright (C) 2008 Imre Kaloz <kaloz@openwrt.org>
  *
  *  Parts of this file are based on Atheros' 2.6.15 BSP
@@ -23,8 +23,8 @@
 #include <asm/mach-ath79/ar71xx_regs.h>
 #include "common.h"
 
-static unsigned int ath79_ip2_flush_reg;
-static unsigned int ath79_ip3_flush_reg;
+static void (*ath79_ip2_handler)(void);
+static void (*ath79_ip3_handler)(void);
 
 static void ath79_misc_irq_handler(unsigned int irq, struct irq_desc *desc)
 {
@@ -152,10 +152,8 @@ asmlinkage void plat_irq_dispatch(void)
 	if (pending & STATUSF_IP7)
 		do_IRQ(ATH79_CPU_IRQ_TIMER);
 
-	else if (pending & STATUSF_IP2) {
-		ath79_ddr_wb_flush(ath79_ip2_flush_reg);
-		do_IRQ(ATH79_CPU_IRQ_IP2);
-	}
+	else if (pending & STATUSF_IP2)
+		ath79_ip2_handler();
 
 	else if (pending & STATUSF_IP4)
 		do_IRQ(ATH79_CPU_IRQ_GE0);
@@ -163,10 +161,8 @@ asmlinkage void plat_irq_dispatch(void)
 	else if (pending & STATUSF_IP5)
 		do_IRQ(ATH79_CPU_IRQ_GE1);
 
-	else if (pending & STATUSF_IP3) {
-		ath79_ddr_wb_flush(ath79_ip3_flush_reg);
-		do_IRQ(ATH79_CPU_IRQ_USB);
-	}
+	else if (pending & STATUSF_IP3)
+		ath79_ip3_handler();
 
 	else if (pending & STATUSF_IP6)
 		do_IRQ(ATH79_CPU_IRQ_MISC);
@@ -175,22 +171,78 @@ asmlinkage void plat_irq_dispatch(void)
 		spurious_interrupt();
 }
 
+/*
+ * The IP2/IP3 lines are tied to a PCI/WMAC/USB device. Drivers for
+ * these devices typically allocate coherent DMA memory, however the
+ * DMA controller may still have some unsynchronized data in the FIFO.
+ * Issue a flush in the handlers to ensure that the driver sees
+ * the update.
+ */
+static void ar71xx_ip2_handler(void)
+{
+	ath79_ddr_wb_flush(AR71XX_DDR_REG_FLUSH_PCI);
+	do_IRQ(ATH79_CPU_IRQ_IP2);
+}
+
+static void ar724x_ip2_handler(void)
+{
+	ath79_ddr_wb_flush(AR724X_DDR_REG_FLUSH_PCIE);
+	do_IRQ(ATH79_CPU_IRQ_IP2);
+}
+
+static void ar913x_ip2_handler(void)
+{
+	ath79_ddr_wb_flush(AR913X_DDR_REG_FLUSH_WMAC);
+	do_IRQ(ATH79_CPU_IRQ_IP2);
+}
+
+static void ar933x_ip2_handler(void)
+{
+	ath79_ddr_wb_flush(AR933X_DDR_REG_FLUSH_WMAC);
+	do_IRQ(ATH79_CPU_IRQ_IP2);
+}
+
+static void ar71xx_ip3_handler(void)
+{
+	ath79_ddr_wb_flush(AR71XX_DDR_REG_FLUSH_USB);
+	do_IRQ(ATH79_CPU_IRQ_USB);
+}
+
+static void ar724x_ip3_handler(void)
+{
+	ath79_ddr_wb_flush(AR724X_DDR_REG_FLUSH_USB);
+	do_IRQ(ATH79_CPU_IRQ_USB);
+}
+
+static void ar913x_ip3_handler(void)
+{
+	ath79_ddr_wb_flush(AR913X_DDR_REG_FLUSH_USB);
+	do_IRQ(ATH79_CPU_IRQ_USB);
+}
+
+static void ar933x_ip3_handler(void)
+{
+	ath79_ddr_wb_flush(AR933X_DDR_REG_FLUSH_USB);
+	do_IRQ(ATH79_CPU_IRQ_USB);
+}
+
 void __init arch_init_irq(void)
 {
 	if (soc_is_ar71xx()) {
-		ath79_ip2_flush_reg = AR71XX_DDR_REG_FLUSH_PCI;
-		ath79_ip3_flush_reg = AR71XX_DDR_REG_FLUSH_USB;
+		ath79_ip2_handler = ar71xx_ip2_handler;
+		ath79_ip3_handler = ar71xx_ip3_handler;
 	} else if (soc_is_ar724x()) {
-		ath79_ip2_flush_reg = AR724X_DDR_REG_FLUSH_PCIE;
-		ath79_ip3_flush_reg = AR724X_DDR_REG_FLUSH_USB;
+		ath79_ip2_handler = ar724x_ip2_handler;
+		ath79_ip3_handler = ar724x_ip3_handler;
 	} else if (soc_is_ar913x()) {
-		ath79_ip2_flush_reg = AR913X_DDR_REG_FLUSH_WMAC;
-		ath79_ip3_flush_reg = AR913X_DDR_REG_FLUSH_USB;
+		ath79_ip2_handler = ar913x_ip2_handler;
+		ath79_ip3_handler = ar913x_ip3_handler;
 	} else if (soc_is_ar933x()) {
-		ath79_ip2_flush_reg = AR933X_DDR_REG_FLUSH_WMAC;
-		ath79_ip3_flush_reg = AR933X_DDR_REG_FLUSH_USB;
-	} else
+		ath79_ip2_handler = ar933x_ip2_handler;
+		ath79_ip3_handler = ar933x_ip3_handler;
+	} else {
 		BUG();
+	}
 
 	cp0_perfcount_irq = ATH79_MISC_IRQ_PERFC;
 	mips_cpu_irq_init();