1 files changed, 11 insertions, 0 deletions

diff --git a/arch/parisc/kernel/traps.c b/arch/parisc/kernel/traps.c
index 68e671a11987..71d31274d782 100644
--- a/arch/parisc/kernel/traps.c
+++ b/arch/parisc/kernel/traps.c
@@ -837,6 +837,17 @@ void __init initialize_ivt(const void *iva)
         if (pdc_instr(&instr) == PDC_OK)
                 ivap[0] = instr;
 
+        /*
+         * Rules for the checksum of the HPMC handler:
+         * 1. The IVA does not point to PDC/PDH space (ie: the OS has installed
+         *    its own IVA).
+         * 2. The word at IVA + 32 is nonzero.
+         * 3. If Length (IVA + 60) is not zero, then Length (IVA + 60) and
+         *    Address (IVA + 56) are word-aligned.
+         * 4. The checksum of the 8 words starting at IVA + 32 plus the sum of
+         *    the Length/4 words starting at Address is zero.
+         */
+
         /* Compute Checksum for HPMC handler */
         length = os_hpmc_size;
         ivap[7] = length;