sparc32,leon: Implemented SMP IPIs for LEON CPU

This patch implements SMP IPIs on LEON using software generated
IRQs to signal between CPUs.

The IPI IRQ number is set by using the ipi_num property in the
device tree, or defaults to 13. LEON SMP systems should reserve
IRQ 13 (and IRQ 15) to Linux in order for the defaults to work.

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

3 files changed, 126 insertions, 3 deletions

diff --git a/arch/sparc/include/asm/leon.h b/arch/sparc/include/asm/leon.h
index f1598ca255f0..6bdaf1e43d2a 100644
--- a/arch/sparc/include/asm/leon.h
+++ b/arch/sparc/include/asm/leon.h
@@ -215,7 +215,7 @@ static inline int sparc_leon3_cpuid(void)
 #endif /*!__ASSEMBLY__*/
 
 #ifdef CONFIG_SMP
-# define LEON3_IRQ_RESCHEDULE           13
+# define LEON3_IRQ_IPI_DEFAULT          13
 # define LEON3_IRQ_TICKER               (leon3_ticker_irq)
 # define LEON3_IRQ_CROSS_CALL           15
 #endif
@@ -351,9 +351,11 @@ void leon_enable_irq_cpu(unsigned int irq_nr, unsigned int cpu);
 extern irqreturn_t leon_percpu_timer_interrupt(int irq, void *unused);
 
 extern unsigned int real_irq_entry[];
+extern unsigned int smpleon_ipi[];
 extern unsigned int patchme_maybe_smp_msg[];
 extern unsigned int t_nmi[], linux_trap_ipi15_leon[];
 extern unsigned int linux_trap_ipi15_sun4m[];
+extern int leon_ipi_irq;
 
 #endif /* CONFIG_SMP */
 
diff --git a/arch/sparc/kernel/entry.S b/arch/sparc/kernel/entry.S
index 1879739c9588..d759cf31c8ee 100644
--- a/arch/sparc/kernel/entry.S
+++ b/arch/sparc/kernel/entry.S
@@ -401,6 +401,22 @@ linux_trap_ipi15_sun4d:
 1:      b,a     1b
 
 #ifdef CONFIG_SPARC_LEON
+        .globl  smpleon_ipi
+        .extern leon_ipi_interrupt
+        /* SMP per-cpu IPI interrupts are handled specially. */
+smpleon_ipi:
+        SAVE_ALL
+        or      %l0, PSR_PIL, %g2
+        wr      %g2, 0x0, %psr
+        WRITE_PAUSE
+        wr      %g2, PSR_ET, %psr
+        WRITE_PAUSE
+        call    leonsmp_ipi_interrupt
+         add    %sp, STACKFRAME_SZ, %o1 ! pt_regs
+        wr      %l0, PSR_ET, %psr
+        WRITE_PAUSE
+        RESTORE_ALL
+
         .align  4
         .globl  linux_trap_ipi15_leon
 linux_trap_ipi15_leon:
diff --git a/arch/sparc/kernel/leon_smp.c b/arch/sparc/kernel/leon_smp.c
index de9506d9ad7d..d95e456a04b6 100644
--- a/arch/sparc/kernel/leon_smp.c
+++ b/arch/sparc/kernel/leon_smp.c
@@ -14,6 +14,7 @@
 #include <linux/smp.h>
 #include <linux/interrupt.h>
 #include <linux/kernel_stat.h>
+#include <linux/of.h>
 #include <linux/init.h>
 #include <linux/spinlock.h>
 #include <linux/mm.h>
@@ -29,6 +30,7 @@
 #include <asm/ptrace.h>
 #include <asm/atomic.h>
 #include <asm/irq_regs.h>
+#include <asm/traps.h>
 
 #include <asm/delay.h>
 #include <asm/irq.h>
@@ -52,6 +54,10 @@ static int smp_processors_ready;
 extern volatile unsigned long cpu_callin_map[NR_CPUS];
 extern cpumask_t smp_commenced_mask;
 void __init leon_configure_cache_smp(void);
+static void leon_ipi_init(void);
+
+/* IRQ number of LEON IPIs */
+int leon_ipi_irq = LEON3_IRQ_IPI_DEFAULT;
 
 static inline unsigned long do_swap(volatile unsigned long *ptr,
                                     unsigned long val)
@@ -176,13 +182,16 @@ void __init leon_boot_cpus(void)
         int nrcpu = leon_smp_nrcpus();
         int me = smp_processor_id();
 
+        /* Setup IPI */
+        leon_ipi_init();
+
         printk(KERN_INFO "%d:(%d:%d) cpus mpirq at 0x%x\n", (unsigned int)me,
                (unsigned int)nrcpu, (unsigned int)NR_CPUS,
                (unsigned int)&(leon3_irqctrl_regs->mpstatus));
 
         leon_enable_irq_cpu(LEON3_IRQ_CROSS_CALL, me);
         leon_enable_irq_cpu(LEON3_IRQ_TICKER, me);
-        leon_enable_irq_cpu(LEON3_IRQ_RESCHEDULE, me);
+        leon_enable_irq_cpu(leon_ipi_irq, me);
 
         leon_smp_setbroadcast(1 << LEON3_IRQ_TICKER);
 
@@ -237,7 +246,7 @@ int __cpuinit leon_boot_one_cpu(int i)
         } else {
                 leon_enable_irq_cpu(LEON3_IRQ_CROSS_CALL, i);
                 leon_enable_irq_cpu(LEON3_IRQ_TICKER, i);
-                leon_enable_irq_cpu(LEON3_IRQ_RESCHEDULE, i);
+                leon_enable_irq_cpu(leon_ipi_irq, i);
         }
 
         local_flush_cache_all();
@@ -293,6 +302,99 @@ void leon_irq_rotate(int cpu)
 {
 }
 
+struct leon_ipi_work {
+        int single;
+        int msk;
+        int resched;
+};
+
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct leon_ipi_work, leon_ipi_work);
+
+/* Initialize IPIs on the LEON, in order to save IRQ resources only one IRQ
+ * is used for all three types of IPIs.
+ */
+static void __init leon_ipi_init(void)
+{
+        int cpu, len;
+        struct leon_ipi_work *work;
+        struct property *pp;
+        struct device_node *rootnp;
+        struct tt_entry *trap_table;
+        unsigned long flags;
+
+        /* Find IPI IRQ or stick with default value */
+        rootnp = of_find_node_by_path("/ambapp0");
+        if (rootnp) {
+                pp = of_find_property(rootnp, "ipi_num", &len);
+                if (pp && (*(int *)pp->value))
+                        leon_ipi_irq = *(int *)pp->value;
+        }
+        printk(KERN_INFO "leon: SMP IPIs at IRQ %d\n", leon_ipi_irq);
+
+        /* Adjust so that we jump directly to smpleon_ipi */
+        local_irq_save(flags);
+        trap_table = &sparc_ttable[SP_TRAP_IRQ1 + (leon_ipi_irq - 1)];
+        trap_table->inst_three += smpleon_ipi - real_irq_entry;
+        local_flush_cache_all();
+        local_irq_restore(flags);
+
+        for_each_possible_cpu(cpu) {
+                work = &per_cpu(leon_ipi_work, cpu);
+                work->single = work->msk = work->resched = 0;
+        }
+}
+
+static void leon_ipi_single(int cpu)
+{
+        struct leon_ipi_work *work = &per_cpu(leon_ipi_work, cpu);
+
+        /* Mark work */
+        work->single = 1;
+
+        /* Generate IRQ on the CPU */
+        set_cpu_int(cpu, leon_ipi_irq);
+}
+
+static void leon_ipi_mask_one(int cpu)
+{
+        struct leon_ipi_work *work = &per_cpu(leon_ipi_work, cpu);
+
+        /* Mark work */
+        work->msk = 1;
+
+        /* Generate IRQ on the CPU */
+        set_cpu_int(cpu, leon_ipi_irq);
+}
+
+static void leon_ipi_resched(int cpu)
+{
+        struct leon_ipi_work *work = &per_cpu(leon_ipi_work, cpu);
+
+        /* Mark work */
+        work->resched = 1;
+
+        /* Generate IRQ on the CPU (any IRQ will cause resched) */
+        set_cpu_int(cpu, leon_ipi_irq);
+}
+
+void leonsmp_ipi_interrupt(void)
+{
+        struct leon_ipi_work *work = &__get_cpu_var(leon_ipi_work);
+
+        if (work->single) {
+                work->single = 0;
+                smp_call_function_single_interrupt();
+        }
+        if (work->msk) {
+                work->msk = 0;
+                smp_call_function_interrupt();
+        }
+        if (work->resched) {
+                work->resched = 0;
+                smp_resched_interrupt();
+        }
+}
+
 static struct smp_funcall {
         smpfunc_t func;
         unsigned long arg1;
@@ -446,6 +548,9 @@ void __init leon_init_smp(void)
         BTFIXUPSET_CALL(smp_cross_call, leon_cross_call, BTFIXUPCALL_NORM);
         BTFIXUPSET_CALL(__hard_smp_processor_id, __leon_processor_id,
                         BTFIXUPCALL_NORM);
+        BTFIXUPSET_CALL(smp_ipi_resched, leon_ipi_resched, BTFIXUPCALL_NORM);
+        BTFIXUPSET_CALL(smp_ipi_single, leon_ipi_single, BTFIXUPCALL_NORM);
+        BTFIXUPSET_CALL(smp_ipi_mask_one, leon_ipi_mask_one, BTFIXUPCALL_NORM);
 }
 
 #endif /* CONFIG_SPARC_LEON */