powerpc/mpic: Add "last-interrupt-source" property to override hardware

The FreeScale PowerQUICC-III-compatible (mpc85xx/mpc86xx) MPICs do not
correctly report the number of hardware interrupt sources, so software
needs to override the detected value with "256".

To avoid needing to write custom board-specific code to detect that
scenario, allow it to be easily overridden in the device-tree.

Signed-off-by: Kyle Moffett <Kyle.D.Moffett@boeing.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 26 insertions, 20 deletions

diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
index cbffeb742d66..90171d447c3d 100644
--- a/arch/powerpc/sysdev/mpic.c
+++ b/arch/powerpc/sysdev/mpic.c
@@ -1149,6 +1149,7 @@ struct mpic * __init mpic_alloc(struct device_node *node,
         u32 greg_feature;
         const char *vers;
         const u32 *psrc;
+        u32 last_irq;
 
         /* Default MPIC search parameters */
         static const struct of_device_id __initconst mpic_device_id[] = {
@@ -1220,7 +1221,6 @@ struct mpic * __init mpic_alloc(struct device_node *node,
         mpic->hc_tm = mpic_tm_chip;
         mpic->hc_tm.name = name;
 
-        mpic->isu_size = isu_size;
         mpic->num_sources = 0; /* so far */
 
         if (mpic->flags & MPIC_LARGE_VECTORS)
@@ -1308,20 +1308,6 @@ struct mpic * __init mpic_alloc(struct device_node *node,
                            | MPIC_GREG_GCONF_MCK);
 
         /*
-         * Read feature register.  For non-ISU MPICs, num sources as well. On
-         * ISU MPICs, sources are counted as ISUs are added
-         */
-        greg_feature = mpic_read(mpic->gregs, MPIC_INFO(GREG_FEATURE_0));
-        if (isu_size == 0) {
-                if (irq_count)
-                        mpic->num_sources = irq_count;
-                else
-                        mpic->num_sources =
-                                ((greg_feature & MPIC_GREG_FEATURE_LAST_SRC_MASK)
-                                 >> MPIC_GREG_FEATURE_LAST_SRC_SHIFT) + 1;
-        }
-
-        /*
          * The MPIC driver will crash if there are more cores than we
          * can initialize, so we may as well catch that problem here.
          */
@@ -1336,18 +1322,38 @@ struct mpic * __init mpic_alloc(struct device_node *node,
                          0x1000);
         }
 
+        /*
+         * Read feature register.  For non-ISU MPICs, num sources as well. On
+         * ISU MPICs, sources are counted as ISUs are added
+         */
+        greg_feature = mpic_read(mpic->gregs, MPIC_INFO(GREG_FEATURE_0));
+
+        /*
+         * By default, the last source number comes from the MPIC, but the
+         * device-tree and board support code can override it on buggy hw.
+         */
+        last_irq = (greg_feature & MPIC_GREG_FEATURE_LAST_SRC_MASK)
+                                >> MPIC_GREG_FEATURE_LAST_SRC_SHIFT;
+        of_property_read_u32(mpic->node, "last-interrupt-source", &last_irq);
+        if (irq_count)
+                last_irq = irq_count - 1;
+
         /* Initialize main ISU if none provided */
-        if (mpic->isu_size == 0) {
-                mpic->isu_size = mpic->num_sources;
+        if (!isu_size) {
+                isu_size = last_irq + 1;
+                mpic->num_sources = isu_size;
                 mpic_map(mpic, mpic->paddr, &mpic->isus[0],
-                         MPIC_INFO(IRQ_BASE), MPIC_INFO(IRQ_STRIDE) * mpic->isu_size);
+                                MPIC_INFO(IRQ_BASE),
+                                MPIC_INFO(IRQ_STRIDE) * isu_size);
         }
+
+        mpic->isu_size = isu_size;
         mpic->isu_shift = 1 + __ilog2(mpic->isu_size - 1);
         mpic->isu_mask = (1 << mpic->isu_shift) - 1;
 
         mpic->irqhost = irq_alloc_host(mpic->node, IRQ_HOST_MAP_LINEAR,
-                                       isu_size ? isu_size : mpic->num_sources,
-                                       &mpic_host_ops, intvec_top + 1);
+                                       mpic->isu_size, &mpic_host_ops,
+                                       intvec_top + 1);
 
         /*
          * FIXME: The code leaks the MPIC object and mappings here; this