target/hppa: Fix PDC address translation on PA2.0 with PSW.W=0

Fix the address translation for PDC space on PA2.0 if PSW.W=0.
Basically, for any address in the 32-bit PDC range from 0xf0000000 to
0xf1000000 keep the lower 32-bits and just set the upper 32-bits to
0xfffffff0.

This mapping fixes the emulated power button in PDC space for 32- and
64-bit machines and is how the physical C3700 machine seems to map
PDC.

Figures H-10 and H-11 in the parisc2.0 spec [1] show that the 32-bit
region will be mapped somewhere into a higher and bigger 64-bit PDC
space.  The start and end of this 64-bit space is defined by the
physical address bits. But the figures don't specifiy where exactly the
mapping will start inside that region. Tests on a real HP C3700
regarding the address of the power button indicate, that the lower
32-bits will stay the same though.
[1] https://parisc.wiki.kernel.org/images-parisc/7/73/Parisc2.0.pdf

Signed-off-by: Helge Deller <deller@gmx.de>
Tested-by: Bruno Haible <bruno@clisp.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 8 insertions, 2 deletions

diff --git a/target/hppa/mem_helper.c b/target/hppa/mem_helper.c
index 08abd1a..4c28c58 100644
--- a/target/hppa/mem_helper.c
+++ b/target/hppa/mem_helper.c
@@ -55,8 +55,14 @@ hwaddr hppa_abs_to_phys_pa2_w0(vaddr addr)
         /* I/O address space */
         addr = (int32_t)addr;
     } else {
-        /* PDC address space */
-        addr &= MAKE_64BIT_MASK(0, 24);
+        /*
+         * PDC address space:
+         * Figures H-10 and H-11 of the parisc2.0 spec do not specify
+         * where to map into the 64-bit PDC address space.
+         * We map with an offset which equals the 32-bit address, which
+         * is what can be seen on physical machines too.
+         */
+        addr = (uint32_t)addr;
         addr |= -1ull << (TARGET_PHYS_ADDR_SPACE_BITS - 4);
     }
     return addr;