sm501: Do not clear read only bits when writing registers

When writing registers that have read only bits we have to avoid
changing these bits as they may have non zero values. Make sure we use
the correct masks to mask out read only and reserved bits when
changing registers.

Also remove extra spaces from dram_control and arbitration_control
assignments.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

1 files changed, 9 insertions, 6 deletions

diff --git a/hw/display/sm501.c b/hw/display/sm501.c
index e47be99451..ca0840f6fa 100644
--- a/hw/display/sm501.c
+++ b/hw/display/sm501.c
@@ -836,27 +836,30 @@ static void sm501_system_config_write(void *opaque, hwaddr addr,
 
     switch (addr) {
     case SM501_SYSTEM_CONTROL:
-        s->system_control = value & 0xE300B8F7;
+        s->system_control &= 0x10DB0000;
+        s->system_control |= value & 0xEF00B8F7;
         break;
     case SM501_MISC_CONTROL:
-        s->misc_control = value & 0xFF7FFF20;
+        s->misc_control &= 0xEF;
+        s->misc_control |= value & 0xFF7FFF10;
         break;
     case SM501_GPIO31_0_CONTROL:
         s->gpio_31_0_control = value;
         break;
     case SM501_GPIO63_32_CONTROL:
-        s->gpio_63_32_control = value;
+        s->gpio_63_32_control = value & 0xFF80FFFF;
         break;
     case SM501_DRAM_CONTROL:
         s->local_mem_size_index = (value >> 13) & 0x7;
         /* TODO : check validity of size change */
-        s->dram_control |=  value & 0x7FFFFFC3;
+        s->dram_control &= 0x80000000;
+        s->dram_control |= value & 0x7FFFFFC3;
         break;
     case SM501_ARBTRTN_CONTROL:
-        s->arbitration_control =  value & 0x37777777;
+        s->arbitration_control = value & 0x37777777;
         break;
     case SM501_IRQ_MASK:
-        s->irq_mask = value;
+        s->irq_mask = value & 0xFFDF3F5F;
         break;
     case SM501_MISC_TIMING:
         s->misc_timing = value & 0xF31F1FFF;