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https://github.com/antonblanchard/microwatt.git
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750b3a8e28
This adds a TLB to dcache, providing the ability to translate addresses for loads and stores. No protection mechanism has been implemented yet. The MSR_DR bit controls whether addresses are translated through the TLB. The TLB is a fixed-pagesize, set-associative cache. Currently the page size is 4kB and the TLB is 2-way set associative with 64 entries per set. This implements the tlbie instruction. RB bits 10 and 11 control whether the whole TLB is invalidated (if either bit is 1) or just a single entry corresponding to the effective page number in bits 12-63 of RB. As an extension until we get a hardware page table walk, a tlbie instruction with RB bits 9-11 set to 001 will load an entry into the TLB. The TLB entry value is in RS in the format of a radix PTE. Currently there is no proper handling of TLB misses. The load or store will not be performed but no interrupt is generated. In order to make timing at 100MHz on the Arty A7-100, we compare the real address from each way of the TLB with the tag from each way of the cache in parallel (requiring # TLB ways * # cache ways comparators). Then the result is selected based on which way hit in the TLB. That avoids a timing path going through the TLB EA comparators, the multiplexer that selects the RA, and the cache tag comparators. The hack where addresses of the form 0xc------- are marked as cache-inhibited is kept for now but restricted to real-mode accesses. Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
95 lines
2.9 KiB
VHDL
95 lines
2.9 KiB
VHDL
library ieee;
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use ieee.std_logic_1164.all;
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package decode_types is
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type insn_type_t is (OP_ILLEGAL, OP_NOP, OP_ADD,
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OP_ADDPCIS, OP_AND, OP_ATTN, OP_B, OP_BC, OP_BCREG,
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OP_BPERM, OP_CMP, OP_CMPB, OP_CMPEQB, OP_CMPRB,
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OP_CNTZ, OP_CROP,
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OP_DARN, OP_DCBF, OP_DCBST, OP_DCBT, OP_DCBTST,
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OP_DCBZ, OP_DIV, OP_DIVE, OP_EXTS,
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OP_EXTSWSLI, OP_ICBI, OP_ICBT, OP_ISEL, OP_ISYNC,
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OP_LOAD, OP_STORE, OP_MADDHD, OP_MADDHDU, OP_MADDLD,
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OP_MCRXR, OP_MCRXRX, OP_MFCR, OP_MFMSR, OP_MFSPR, OP_MOD,
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OP_MTCRF, OP_MTMSRD, OP_MTSPR, OP_MUL_L64,
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OP_MUL_H64, OP_MUL_H32, OP_OR,
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OP_POPCNT, OP_PRTY, OP_RFID,
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OP_RLC, OP_RLCL, OP_RLCR, OP_SC, OP_SETB,
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OP_SHL, OP_SHR,
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OP_SYNC, OP_TLBIE, OP_TRAP,
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OP_XOR
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);
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type input_reg_a_t is (NONE, RA, RA_OR_ZERO, SPR);
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type input_reg_b_t is (NONE, RB, CONST_UI, CONST_SI, CONST_SI_HI, CONST_UI_HI, CONST_LI, CONST_BD, CONST_DS, CONST_M1, CONST_SH, CONST_SH32, SPR);
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type input_reg_c_t is (NONE, RS);
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type output_reg_a_t is (NONE, RT, RA, SPR);
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type rc_t is (NONE, ONE, RC);
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type carry_in_t is (ZERO, CA, ONE);
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constant SH_OFFSET : integer := 0;
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constant MB_OFFSET : integer := 1;
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constant ME_OFFSET : integer := 1;
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constant SH32_OFFSET : integer := 0;
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constant MB32_OFFSET : integer := 1;
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constant ME32_OFFSET : integer := 2;
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constant FXM_OFFSET : integer := 0;
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constant BO_OFFSET : integer := 0;
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constant BI_OFFSET : integer := 1;
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constant BH_OFFSET : integer := 2;
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constant BF_OFFSET : integer := 0;
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constant L_OFFSET : integer := 1;
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constant TOO_OFFSET : integer := 0;
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type unit_t is (NONE, ALU, LDST);
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type length_t is (NONE, is1B, is2B, is4B, is8B);
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type decode_rom_t is record
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unit : unit_t;
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insn_type : insn_type_t;
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input_reg_a : input_reg_a_t;
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input_reg_b : input_reg_b_t;
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input_reg_c : input_reg_c_t;
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output_reg_a : output_reg_a_t;
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input_cr : std_ulogic;
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output_cr : std_ulogic;
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invert_a : std_ulogic;
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invert_out : std_ulogic;
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input_carry : carry_in_t;
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output_carry : std_ulogic;
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-- load/store signals
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length : length_t;
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byte_reverse : std_ulogic;
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sign_extend : std_ulogic;
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update : std_ulogic;
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reserve : std_ulogic;
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-- multiplier and ALU signals
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is_32bit : std_ulogic;
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is_signed : std_ulogic;
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rc : rc_t;
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lr : std_ulogic;
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sgl_pipe : std_ulogic;
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end record;
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constant decode_rom_init : decode_rom_t := (unit => NONE,
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insn_type => OP_ILLEGAL, input_reg_a => NONE,
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input_reg_b => NONE, input_reg_c => NONE,
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output_reg_a => NONE, input_cr => '0', output_cr => '0',
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invert_a => '0', invert_out => '0', input_carry => ZERO, output_carry => '0',
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length => NONE, byte_reverse => '0', sign_extend => '0',
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update => '0', reserve => '0', is_32bit => '0',
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is_signed => '0', rc => NONE, lr => '0', sgl_pipe => '0');
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end decode_types;
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package body decode_types is
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end decode_types;
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