Add to MMU init: bypass cache in MMIO page

[pdp11-memory-test] / pdp11_mmu.c

// (c) 2020 Aaron Taylor <ataylor at subgeniuskitty dot com>
// See License.txt file for copyright and license details.

#include <stdint.h>
#include "pdp11_register.h"

void
init_mmu(void)
{

   /*
    * First populate the relocation registers, all zero since we want an
    * identity mapping, except the highest page that we remap to the physical MMIO
    * range.
    */
   SET(KISAR0,PAR_PAF,0000000);
   SET(KISAR1,PAR_PAF,0000000);
   SET(KISAR2,PAR_PAF,0000000);
   SET(KISAR3,PAR_PAF,0000000);
   SET(KISAR4,PAR_PAF,0000000);
   SET(KISAR5,PAR_PAF,0000000);
   SET(KISAR6,PAR_PAF,0000000);
   SET(KISAR7,PAR_PAF,0177600);

   /*
    * Now populate the page descriptor registers. See EK-KDJ1B-UG page 1-19
    * for details of each field.
    */
   uint16_t data = 0;
   SET(data,PDR_BYPASCACHE,0);
   SET(data,PDR_PAGELEN,0177);
   SET(data,PDR_PAGEWRITEN,0);
   SET(data,PDR_EXPANDDIR,0);
   SET(data,PDR_ACCESSCTRL,03);

   KISDR0 = data;
   KISDR1 = data;
   KISDR2 = data;
   KISDR3 = data;
   KISDR4 = data;
   KISDR5 = data;
   KISDR6 = data;

   SET(data,PDR_BYPASCACHE,1);

   KISDR7 = data;

   /*
    * Enable the MMU with a 22-bit mapping.
    */
   SET(MMR3,MMR3_KRNSPLTID,0);
   SET(MMR3,MMR3_EN_22BIT,1);
   SET(MMR0,MMR0_EN_MMU,1);
}