[POWERPC] spufs: rework class 0 and 1 interrupt handling

Based on original patches from
 Arnd Bergmann <arnd.bergman@de.ibm.com>; and
 Luke Browning <lukebr@linux.vnet.ibm.com>

Currently, spu contexts need to be loaded to the SPU in order to take
class 0 and class 1 exceptions.

This change makes the actual interrupt-handlers much simpler (ie,
set the exception information in the context save area), and defers the
handling code to the spufs_handle_class[01] functions, called from
spufs_run_spu.

This should improve the concurrency of the spu scheduling leading to
greater SPU utilization when SPUs are overcommited.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

8 files changed, 108 insertions, 121 deletions

diff --git a/arch/powerpc/platforms/cell/spu_base.c b/arch/powerpc/platforms/cell/spu_base.c
index a560277b3ad7..fb266ae32095 100644
--- a/arch/powerpc/platforms/cell/spu_base.c
+++ b/arch/powerpc/platforms/cell/spu_base.c
@@ -132,27 +132,6 @@ int spu_64k_pages_available(void)
 }
 EXPORT_SYMBOL_GPL(spu_64k_pages_available);
 
-static int __spu_trap_invalid_dma(struct spu *spu)
-{
-        pr_debug("%s\n", __FUNCTION__);
-        spu->dma_callback(spu, SPE_EVENT_INVALID_DMA);
-        return 0;
-}
-
-static int __spu_trap_dma_align(struct spu *spu)
-{
-        pr_debug("%s\n", __FUNCTION__);
-        spu->dma_callback(spu, SPE_EVENT_DMA_ALIGNMENT);
-        return 0;
-}
-
-static int __spu_trap_error(struct spu *spu)
-{
-        pr_debug("%s\n", __FUNCTION__);
-        spu->dma_callback(spu, SPE_EVENT_SPE_ERROR);
-        return 0;
-}
-
 static void spu_restart_dma(struct spu *spu)
 {
         struct spu_priv2 __iomem *priv2 = spu->priv2;
@@ -252,10 +231,12 @@ static int __spu_trap_data_map(struct spu *spu, unsigned long ea, u64 dsisr)
                 return 1;
         }
 
+        spu->class_0_pending = 0;
         spu->dar = ea;
         spu->dsisr = dsisr;
-        mb();
+
         spu->stop_callback(spu);
+
         return 0;
 }
 
@@ -335,12 +316,13 @@ spu_irq_class_0(int irq, void *data)
 
         spu = data;
 
+        spin_lock(&spu->register_lock);
         mask = spu_int_mask_get(spu, 0);
-        stat = spu_int_stat_get(spu, 0);
-        stat &= mask;
+        stat = spu_int_stat_get(spu, 0) & mask;
 
-        spin_lock(&spu->register_lock);
         spu->class_0_pending |= stat;
+        spu->dsisr = spu_mfc_dsisr_get(spu);
+        spu->dar = spu_mfc_dar_get(spu);
         spin_unlock(&spu->register_lock);
 
         spu->stop_callback(spu);
@@ -350,31 +332,6 @@ spu_irq_class_0(int irq, void *data)
         return IRQ_HANDLED;
 }
 
-int
-spu_irq_class_0_bottom(struct spu *spu)
-{
-        unsigned long flags;
-        unsigned long stat;
-
-        spin_lock_irqsave(&spu->register_lock, flags);
-        stat = spu->class_0_pending;
-        spu->class_0_pending = 0;
-
-        if (stat & CLASS0_DMA_ALIGNMENT_INTR)
-                __spu_trap_dma_align(spu);
-
-        if (stat & CLASS0_INVALID_DMA_COMMAND_INTR)
-                __spu_trap_invalid_dma(spu);
-
-        if (stat & CLASS0_SPU_ERROR_INTR)
-                __spu_trap_error(spu);
-
-        spin_unlock_irqrestore(&spu->register_lock, flags);
-
-        return (stat & CLASS0_INTR_MASK) ? -EIO : 0;
-}
-EXPORT_SYMBOL_GPL(spu_irq_class_0_bottom);
-
 static irqreturn_t
 spu_irq_class_1(int irq, void *data)
 {
diff --git a/arch/powerpc/platforms/cell/spufs/fault.c b/arch/powerpc/platforms/cell/spufs/fault.c
index 0635f292ae19..720e111f1f6a 100644
--- a/arch/powerpc/platforms/cell/spufs/fault.c
+++ b/arch/powerpc/platforms/cell/spufs/fault.c
@@ -28,46 +28,69 @@
 
 #include "spufs.h"
 
-static void spufs_handle_dma_error(struct spu_context *ctx,
+/**
+ * Handle an SPE event, depending on context SPU_CREATE_EVENTS_ENABLED flag.
+ *
+ * If the context was created with events, we just set the return event.
+ * Otherwise, send an appropriate signal to the process.
+ */
+static void spufs_handle_event(struct spu_context *ctx,
                                 unsigned long ea, int type)
 {
+        siginfo_t info;
+
         if (ctx->flags & SPU_CREATE_EVENTS_ENABLED) {
                 ctx->event_return |= type;
                 wake_up_all(&ctx->stop_wq);
-        } else {
-                siginfo_t info;
-                memset(&info, 0, sizeof(info));
-
-                switch (type) {
-                case SPE_EVENT_INVALID_DMA:
-                        info.si_signo = SIGBUS;
-                        info.si_code = BUS_OBJERR;
-                        break;
-                case SPE_EVENT_SPE_DATA_STORAGE:
-                        info.si_signo = SIGBUS;
-                        info.si_addr = (void __user *)ea;
-                        info.si_code = BUS_ADRERR;
-                        break;
-                case SPE_EVENT_DMA_ALIGNMENT:
-                        info.si_signo = SIGBUS;
-                        /* DAR isn't set for an alignment fault :( */
-                        info.si_code = BUS_ADRALN;
-                        break;
-                case SPE_EVENT_SPE_ERROR:
-                        info.si_signo = SIGILL;
-                        info.si_addr = (void __user *)(unsigned long)
-                                ctx->ops->npc_read(ctx) - 4;
-                        info.si_code = ILL_ILLOPC;
-                        break;
-                }
-                if (info.si_signo)
-                        force_sig_info(info.si_signo, &info, current);
+                return;
         }
+
+        memset(&info, 0, sizeof(info));
+
+        switch (type) {
+        case SPE_EVENT_INVALID_DMA:
+                info.si_signo = SIGBUS;
+                info.si_code = BUS_OBJERR;
+                break;
+        case SPE_EVENT_SPE_DATA_STORAGE:
+                info.si_signo = SIGBUS;
+                info.si_addr = (void __user *)ea;
+                info.si_code = BUS_ADRERR;
+                break;
+        case SPE_EVENT_DMA_ALIGNMENT:
+                info.si_signo = SIGBUS;
+                /* DAR isn't set for an alignment fault :( */
+                info.si_code = BUS_ADRALN;
+                break;
+        case SPE_EVENT_SPE_ERROR:
+                info.si_signo = SIGILL;
+                info.si_addr = (void __user *)(unsigned long)
+                        ctx->ops->npc_read(ctx) - 4;
+                info.si_code = ILL_ILLOPC;
+                break;
+        }
+
+        if (info.si_signo)
+                force_sig_info(info.si_signo, &info, current);
 }
 
-void spufs_dma_callback(struct spu *spu, int type)
+int spufs_handle_class0(struct spu_context *ctx)
 {
-        spufs_handle_dma_error(spu->ctx, spu->dar, type);
+        unsigned long stat = ctx->csa.class_0_pending & CLASS0_INTR_MASK;
+
+        if (likely(!stat))
+                return 0;
+
+        if (stat & CLASS0_DMA_ALIGNMENT_INTR)
+                spufs_handle_event(ctx, ctx->csa.dar, SPE_EVENT_DMA_ALIGNMENT);
+
+        if (stat & CLASS0_INVALID_DMA_COMMAND_INTR)
+                spufs_handle_event(ctx, ctx->csa.dar, SPE_EVENT_INVALID_DMA);
+
+        if (stat & CLASS0_SPU_ERROR_INTR)
+                spufs_handle_event(ctx, ctx->csa.dar, SPE_EVENT_SPE_ERROR);
+
+        return -EIO;
 }
 
 /*
@@ -95,16 +118,8 @@ int spufs_handle_class1(struct spu_context *ctx)
          * in time, we can still expect to get the same fault
          * the immediately after the context restore.
          */
-        if (ctx->state == SPU_STATE_RUNNABLE) {
-                ea = ctx->spu->dar;
-                dsisr = ctx->spu->dsisr;
-                ctx->spu->dar= ctx->spu->dsisr = 0;
-        } else {
-                ea = ctx->csa.priv1.mfc_dar_RW;
-                dsisr = ctx->csa.priv1.mfc_dsisr_RW;
-                ctx->csa.priv1.mfc_dar_RW = 0;
-                ctx->csa.priv1.mfc_dsisr_RW = 0;
-        }
+        ea = ctx->csa.dar;
+        dsisr = ctx->csa.dsisr;
 
         if (!(dsisr & (MFC_DSISR_PTE_NOT_FOUND | MFC_DSISR_ACCESS_DENIED)))
                 return 0;
@@ -132,6 +147,14 @@ int spufs_handle_class1(struct spu_context *ctx)
                 ret = spu_handle_mm_fault(current->mm, ea, dsisr, &flt);
 
         spu_acquire(ctx);
+
+        /*
+         * Clear dsisr under ctxt lock after handling the fault, so that
+         * time slicing will not preempt the context while the page fault
+         * handler is running. Context switch code removes mappings.
+         */
+        ctx->csa.dar = ctx->csa.dsisr = 0;
+
         /*
          * If we handled the fault successfully and are in runnable
          * state, restart the DMA.
@@ -152,7 +175,7 @@ int spufs_handle_class1(struct spu_context *ctx)
                 if (ctx->spu)
                         ctx->ops->restart_dma(ctx);
         } else
-                spufs_handle_dma_error(ctx, ea, SPE_EVENT_SPE_DATA_STORAGE);
+                spufs_handle_event(ctx, ea, SPE_EVENT_SPE_DATA_STORAGE);
 
         spuctx_switch_state(ctx, SPU_UTIL_SYSTEM);
         return ret;
diff --git a/arch/powerpc/platforms/cell/spufs/run.c b/arch/powerpc/platforms/cell/spufs/run.c
index b3cc1dd72185..3b3de6c7ee5b 100644
--- a/arch/powerpc/platforms/cell/spufs/run.c
+++ b/arch/powerpc/platforms/cell/spufs/run.c
@@ -15,7 +15,30 @@ void spufs_stop_callback(struct spu *spu)
 {
         struct spu_context *ctx = spu->ctx;
 
-        wake_up_all(&ctx->stop_wq);
+        /*
+         * It should be impossible to preempt a context while an exception
+         * is being processed, since the context switch code is specially
+         * coded to deal with interrupts ... But, just in case, sanity check
+         * the context pointer.  It is OK to return doing nothing since
+         * the exception will be regenerated when the context is resumed.
+         */
+        if (ctx) {
+                /* Copy exception arguments into module specific structure */
+                ctx->csa.class_0_pending = spu->class_0_pending;
+                ctx->csa.dsisr = spu->dsisr;
+                ctx->csa.dar = spu->dar;
+
+                /* ensure that the exception status has hit memory before a
+                 * thread waiting on the context's stop queue is woken */
+                smp_wmb();
+
+                wake_up_all(&ctx->stop_wq);
+        }
+
+        /* Clear callback arguments from spu structure */
+        spu->class_0_pending = 0;
+        spu->dsisr = 0;
+        spu->dar = 0;
 }
 
 static inline int spu_stopped(struct spu_context *ctx, u32 *stat)
@@ -29,9 +52,9 @@ static inline int spu_stopped(struct spu_context *ctx, u32 *stat)
         if (ctx->state != SPU_STATE_RUNNABLE ||
             test_bit(SPU_SCHED_NOTIFY_ACTIVE, &ctx->sched_flags))
                 return 1;
-        pte_fault = spu->dsisr &
+        pte_fault = ctx->csa.dsisr &
             (MFC_DSISR_PTE_NOT_FOUND | MFC_DSISR_ACCESS_DENIED);
-        return (!(*stat & SPU_STATUS_RUNNING) || pte_fault || spu->class_0_pending) ?
+        return (!(*stat & SPU_STATUS_RUNNING) || pte_fault || ctx->csa.class_0_pending) ?
                 1 : 0;
 }
 
@@ -287,18 +310,6 @@ static int spu_process_callback(struct spu_context *ctx)
         return ret;
 }
 
-static inline int spu_process_events(struct spu_context *ctx)
-{
-        struct spu *spu = ctx->spu;
-        int ret = 0;
-
-        if (spu->class_0_pending)
-                ret = spu_irq_class_0_bottom(spu);
-        if (!ret && signal_pending(current))
-                ret = -ERESTARTSYS;
-        return ret;
-}
-
 long spufs_run_spu(struct spu_context *ctx, u32 *npc, u32 *event)
 {
         int ret;
@@ -364,13 +375,20 @@ long spufs_run_spu(struct spu_context *ctx, u32 *npc, u32 *event)
                 if (ret)
                         break;
 
+                ret = spufs_handle_class0(ctx);
+                if (ret)
+                        break;
+
                 if (unlikely(ctx->state != SPU_STATE_RUNNABLE)) {
                         ret = spu_reacquire_runnable(ctx, npc, &status);
                         if (ret)
                                 goto out2;
                         continue;
                 }
-                ret = spu_process_events(ctx);
+
+                if (signal_pending(current))
+                        ret = -ERESTARTSYS;
+
 
         } while (!ret && !(status & (SPU_STATUS_STOPPED_BY_STOP |
                                       SPU_STATUS_STOPPED_BY_HALT |
diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c
index 52215aa2f3c6..82ea576c53a3 100644
--- a/arch/powerpc/platforms/cell/spufs/sched.c
+++ b/arch/powerpc/platforms/cell/spufs/sched.c
@@ -245,7 +245,6 @@ static void spu_bind_context(struct spu *spu, struct spu_context *ctx)
         spu->wbox_callback = spufs_wbox_callback;
         spu->stop_callback = spufs_stop_callback;
         spu->mfc_callback = spufs_mfc_callback;
-        spu->dma_callback = spufs_dma_callback;
         mb();
         spu_unmap_mappings(ctx);
         spu_restore(&ctx->csa, spu);
@@ -433,7 +432,6 @@ static void spu_unbind_context(struct spu *spu, struct spu_context *ctx)
         spu->wbox_callback = NULL;
         spu->stop_callback = NULL;
         spu->mfc_callback = NULL;
-        spu->dma_callback = NULL;
         spu_associate_mm(spu, NULL);
         spu->pid = 0;
         spu->tgid = 0;
diff --git a/arch/powerpc/platforms/cell/spufs/spufs.h b/arch/powerpc/platforms/cell/spufs/spufs.h
index afdddbc8cf68..eaab1b239d02 100644
--- a/arch/powerpc/platforms/cell/spufs/spufs.h
+++ b/arch/powerpc/platforms/cell/spufs/spufs.h
@@ -222,6 +222,7 @@ void spu_gang_add_ctx(struct spu_gang *gang, struct spu_context *ctx);
 
 /* fault handling */
 int spufs_handle_class1(struct spu_context *ctx);
+int spufs_handle_class0(struct spu_context *ctx);
 
 /* affinity */
 struct spu *affinity_check(struct spu_context *ctx);
diff --git a/arch/powerpc/platforms/cell/spufs/switch.c b/arch/powerpc/platforms/cell/spufs/switch.c
index c9600e8e0e16..1a7d7a0f66fc 100644
--- a/arch/powerpc/platforms/cell/spufs/switch.c
+++ b/arch/powerpc/platforms/cell/spufs/switch.c
@@ -2077,10 +2077,6 @@ int spu_save(struct spu_state *prev, struct spu *spu)
         int rc;
 
         acquire_spu_lock(spu);          /* Step 1.     */
-        prev->dar = spu->dar;
-        prev->dsisr = spu->dsisr;
-        spu->dar = 0;
-        spu->dsisr = 0;
         rc = __do_spu_save(prev, spu);  /* Steps 2-53. */
         release_spu_lock(spu);
         if (rc != 0 && rc != 2 && rc != 6) {
@@ -2107,9 +2103,6 @@ int spu_restore(struct spu_state *new, struct spu *spu)
         acquire_spu_lock(spu);
         harvest(NULL, spu);
         spu->slb_replace = 0;
-        new->dar = 0;
-        new->dsisr = 0;
-        spu->class_0_pending = 0;
         rc = __do_spu_restore(new, spu);
         release_spu_lock(spu);
         if (rc) {
diff --git a/include/asm-powerpc/spu.h b/include/asm-powerpc/spu.h
index 816e3dc1f66f..277460476aec 100644
--- a/include/asm-powerpc/spu.h
+++ b/include/asm-powerpc/spu.h
@@ -146,7 +146,6 @@ struct spu {
         void (* ibox_callback)(struct spu *spu);
         void (* stop_callback)(struct spu *spu);
         void (* mfc_callback)(struct spu *spu);
-        void (* dma_callback)(struct spu *spu, int type);
 
         char irq_c0[8];
         char irq_c1[8];
@@ -197,8 +196,6 @@ struct cbe_spu_info {
 extern struct cbe_spu_info cbe_spu_info[];
 
 void spu_init_channels(struct spu *spu);
-int spu_irq_class_0_bottom(struct spu *spu);
-int spu_irq_class_1_bottom(struct spu *spu);
 void spu_irq_setaffinity(struct spu *spu, int cpu);
 
 void spu_setup_kernel_slbs(struct spu *spu, struct spu_lscsa *lscsa,
diff --git a/include/asm-powerpc/spu_csa.h b/include/asm-powerpc/spu_csa.h
index 34da5c685170..0ab6bff86078 100644
--- a/include/asm-powerpc/spu_csa.h
+++ b/include/asm-powerpc/spu_csa.h
@@ -254,7 +254,7 @@ struct spu_state {
         u64 spu_chnldata_RW[32];
         u32 spu_mailbox_data[4];
         u32 pu_mailbox_data[1];
-        u64 dar, dsisr;
+        u64 dar, dsisr, class_0_pending;
         unsigned long suspend_time;
         spinlock_t register_lock;
 };