sparc32, sun4d: Implemented SMP IPIs support for SUN4D machines

The sun4d does not seem to have a distingstion between soft and hard
IRQs. When generating IPIs the generated IRQ looks like a hard IRQ,
this patch adds a "IPI check" in the sun4d irq trap handler at a
predefined IRQ number (SUN4D_IPI_IRQ). Before generating an IPI
a per-cpu memory structure is modified for the "IPI check" to
successfully detect a IPI request to a specific processor, the check
clears the IPI work requested.

All three IPIs (resched, single and cpu-mask) use the same IRQ
number.

The IPI IRQ should preferrably be on a separate IRQ and definitly
not shared with IRQ handlers requesting IRQ with IRQF_SHARED.

Signed-off-by: Daniel Hellstrom <daniel@gaisler.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 0 deletions

diff --git a/arch/sparc/kernel/sun4d_irq.c b/arch/sparc/kernel/sun4d_irq.c
index b830914e32d3..a9ea60eb2c10 100644
--- a/arch/sparc/kernel/sun4d_irq.c
+++ b/arch/sparc/kernel/sun4d_irq.c
@@ -156,6 +156,15 @@ void sun4d_handler_irq(int pil, struct pt_regs *regs)
 
 	cc_set_iclr(1 << pil);
 
+#ifdef CONFIG_SMP
+	/*
+	 * Check IPI data structures after IRQ has been cleared. Hard and Soft
+	 * IRQ can happen at the same time, so both cases are always handled.
+	 */
+	if (pil == SUN4D_IPI_IRQ)
+		sun4d_ipi_interrupt();
+#endif
+
 	old_regs = set_irq_regs(regs);
 	irq_enter();
 	if (sbusl == 0) {