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microwatt/loadstore1.vhdl

987 lines
38 KiB
VHDL

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
library work;
use work.decode_types.all;
use work.common.all;
use work.insn_helpers.all;
use work.helpers.all;
-- 2 cycle LSU
-- We calculate the address in the first cycle
entity loadstore1 is
generic (
HAS_FPU : boolean := true;
-- Non-zero to enable log data collection
LOG_LENGTH : natural := 0
);
port (
clk : in std_ulogic;
rst : in std_ulogic;
l_in : in Execute1ToLoadstore1Type;
e_out : out Loadstore1ToExecute1Type;
l_out : out Loadstore1ToWritebackType;
d_out : out Loadstore1ToDcacheType;
d_in : in DcacheToLoadstore1Type;
m_out : out Loadstore1ToMmuType;
m_in : in MmuToLoadstore1Type;
dc_stall : in std_ulogic;
events : out Loadstore1EventType;
log_out : out std_ulogic_vector(9 downto 0)
);
end loadstore1;
architecture behave of loadstore1 is
-- State machine for unaligned loads/stores
type state_t is (IDLE, -- ready for instruction
MMU_LOOKUP, -- waiting for MMU to look up translation
TLBIE_WAIT, -- waiting for MMU to finish doing a tlbie
FINISH_LFS -- write back converted SP data for lfs*
);
type byte_index_t is array(0 to 7) of unsigned(2 downto 0);
subtype byte_trim_t is std_ulogic_vector(1 downto 0);
type trim_ctl_t is array(0 to 7) of byte_trim_t;
type request_t is record
valid : std_ulogic;
dc_req : std_ulogic;
load : std_ulogic;
store : std_ulogic;
dcache: Implement data TLB 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>
4 years ago
tlbie : std_ulogic;
dcbz : std_ulogic;
read_spr : std_ulogic;
write_spr : std_ulogic;
mmu_op : std_ulogic;
instr_fault : std_ulogic;
load_zero : std_ulogic;
do_update : std_ulogic;
noop : std_ulogic;
mode_32bit : std_ulogic;
addr : std_ulogic_vector(63 downto 0);
addr0 : std_ulogic_vector(63 downto 0);
byte_sel : std_ulogic_vector(7 downto 0);
second_bytes : std_ulogic_vector(7 downto 0);
store_data : std_ulogic_vector(63 downto 0);
instr_tag : instr_tag_t;
write_reg : gspr_index_t;
length : std_ulogic_vector(3 downto 0);
elt_length : std_ulogic_vector(3 downto 0);
byte_reverse : std_ulogic;
brev_mask : unsigned(2 downto 0);
sign_extend : std_ulogic;
update : std_ulogic;
xerc : xer_common_t;
reserve : std_ulogic;
core: Implement quadword loads and stores This implements the lq, stq, lqarx and stqcx. instructions. These instructions all access two consecutive GPRs; for example the "lq %r6,0(%r3)" instruction will load the doubleword at the address in R3 into R7 and the doubleword at address R3 + 8 into R6. To cope with having two GPR sources or destinations, the instruction gets repeated at the decode2 stage, that is, for each lq/stq/lqarx/stqcx. coming in from decode1, two instructions get sent out to execute1. For these instructions, the RS or RT register gets modified on one of the iterations by setting the LSB of the register number. In LE mode, the first iteration uses RS|1 or RT|1 and the second iteration uses RS or RT. In BE mode, this is done the other way around. In order for decode2 to know what endianness is currently in use, we pass the big_endian flag down from icache through decode1 to decode2. This is always in sync with what execute1 is using because only rfid or an interrupt can change MSR[LE], and those operations all cause a flush and redirect. There is now an extra column in the decode tables in decode1 to indicate whether the instruction needs to be repeated. Decode1 also enforces the rule that lq with RT = RT and lqarx with RA = RT or RB = RT are illegal. Decode2 now passes a 'repeat' flag and a 'second' flag to execute1, and execute1 passes them on to loadstore1. The 'repeat' flag is set for both iterations of a repeated instruction, and 'second' is set on the second iteration. Execute1 does not take asynchronous or trace interrupts on the second iteration of a repeated instruction. Loadstore1 uses 'next_addr' for the second iteration of a repeated load/store so that we access the second doubleword of the memory operand. Thus loadstore1 accesses the doublewords in increasing memory order. For 16-byte loads this means that the first iteration writes GPR RT|1. It is possible that RA = RT|1 (this is a legal but non-preferred form), meaning that if the memory operand was misaligned, the first iteration would overwrite RA but then the second iteration might take a page fault, leading to corrupted state. To avoid that possibility, 16-byte loads in LE mode take an alignment interrupt if the operand is not 16-byte aligned. (This is the case anyway for lqarx, and we enforce it for lq as well.) Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
4 years ago
atomic : std_ulogic;
atomic_last : std_ulogic;
rc : std_ulogic;
nc : std_ulogic; -- non-cacheable access
dcache: Implement data TLB 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>
4 years ago
virt_mode : std_ulogic;
priv_mode : std_ulogic;
load_sp : std_ulogic;
sprn : std_ulogic_vector(9 downto 0);
is_slbia : std_ulogic;
align_intr : std_ulogic;
dword_index : std_ulogic;
two_dwords : std_ulogic;
nia : std_ulogic_vector(63 downto 0);
end record;
constant request_init : request_t := (valid => '0', dc_req => '0', load => '0', store => '0', tlbie => '0',
dcbz => '0', read_spr => '0', write_spr => '0', mmu_op => '0',
instr_fault => '0', load_zero => '0', do_update => '0', noop => '0',
mode_32bit => '0', addr => (others => '0'), addr0 => (others => '0'),
byte_sel => x"00", second_bytes => x"00",
store_data => (others => '0'), instr_tag => instr_tag_init,
write_reg => 7x"00", length => x"0",
elt_length => x"0", byte_reverse => '0', brev_mask => "000",
sign_extend => '0', update => '0',
xerc => xerc_init, reserve => '0',
atomic => '0', atomic_last => '0', rc => '0', nc => '0',
virt_mode => '0', priv_mode => '0', load_sp => '0',
sprn => 10x"0", is_slbia => '0', align_intr => '0',
dword_index => '0', two_dwords => '0',
nia => (others => '0'));
type reg_stage1_t is record
req : request_t;
issued : std_ulogic;
end record;
type reg_stage2_t is record
req : request_t;
byte_index : byte_index_t;
use_second : std_ulogic_vector(7 downto 0);
wait_dc : std_ulogic;
wait_mmu : std_ulogic;
one_cycle : std_ulogic;
wr_sel : std_ulogic_vector(1 downto 0);
end record;
type reg_stage3_t is record
state : state_t;
instr_tag : instr_tag_t;
write_enable : std_ulogic;
write_reg : gspr_index_t;
write_data : std_ulogic_vector(63 downto 0);
rc : std_ulogic;
xerc : xer_common_t;
store_done : std_ulogic;
convert_lfs : std_ulogic;
load_data : std_ulogic_vector(63 downto 0);
dar : std_ulogic_vector(63 downto 0);
dsisr : std_ulogic_vector(31 downto 0);
ld_sp_data : std_ulogic_vector(31 downto 0);
ld_sp_nz : std_ulogic;
ld_sp_lz : std_ulogic_vector(5 downto 0);
stage1_en : std_ulogic;
interrupt : std_ulogic;
intr_vec : integer range 0 to 16#fff#;
nia : std_ulogic_vector(63 downto 0);
srr1 : std_ulogic_vector(15 downto 0);
events : Loadstore1EventType;
end record;
signal req_in : request_t;
signal r1, r1in : reg_stage1_t;
signal r2, r2in : reg_stage2_t;
signal r3, r3in : reg_stage3_t;
signal busy : std_ulogic;
signal complete : std_ulogic;
signal in_progress : std_ulogic;
signal flushing : std_ulogic;
signal store_sp_data : std_ulogic_vector(31 downto 0);
signal load_dp_data : std_ulogic_vector(63 downto 0);
signal store_data : std_ulogic_vector(63 downto 0);
signal stage1_issue_enable : std_ulogic;
signal stage1_req : request_t;
signal stage1_dcreq : std_ulogic;
signal stage1_dreq : std_ulogic;
signal stage2_busy_next : std_ulogic;
signal stage3_busy_next : std_ulogic;
-- Generate byte enables from sizes
function length_to_sel(length : in std_logic_vector(3 downto 0)) return std_ulogic_vector is
begin
case length is
when "0001" =>
return "00000001";
when "0010" =>
return "00000011";
when "0100" =>
return "00001111";
when "1000" =>
return "11111111";
when others =>
return "00000000";
end case;
end function length_to_sel;
-- Calculate byte enables
-- This returns 16 bits, giving the select signals for two transfers,
-- to account for unaligned loads or stores
function xfer_data_sel(size : in std_logic_vector(3 downto 0);
address : in std_logic_vector(2 downto 0))
return std_ulogic_vector is
variable longsel : std_ulogic_vector(15 downto 0);
begin
longsel := "00000000" & length_to_sel(size);
return std_ulogic_vector(shift_left(unsigned(longsel),
to_integer(unsigned(address))));
end function xfer_data_sel;
-- 23-bit right shifter for DP -> SP float conversions
function shifter_23r(frac: std_ulogic_vector(22 downto 0); shift: unsigned(4 downto 0))
return std_ulogic_vector is
variable fs1 : std_ulogic_vector(22 downto 0);
variable fs2 : std_ulogic_vector(22 downto 0);
begin
case shift(1 downto 0) is
when "00" =>
fs1 := frac;
when "01" =>
fs1 := '0' & frac(22 downto 1);
when "10" =>
fs1 := "00" & frac(22 downto 2);
when others =>
fs1 := "000" & frac(22 downto 3);
end case;
case shift(4 downto 2) is
when "000" =>
fs2 := fs1;
when "001" =>
fs2 := x"0" & fs1(22 downto 4);
when "010" =>
fs2 := x"00" & fs1(22 downto 8);
when "011" =>
fs2 := x"000" & fs1(22 downto 12);
when "100" =>
fs2 := x"0000" & fs1(22 downto 16);
when others =>
fs2 := x"00000" & fs1(22 downto 20);
end case;
return fs2;
end;
-- 23-bit left shifter for SP -> DP float conversions
function shifter_23l(frac: std_ulogic_vector(22 downto 0); shift: unsigned(4 downto 0))
return std_ulogic_vector is
variable fs1 : std_ulogic_vector(22 downto 0);
variable fs2 : std_ulogic_vector(22 downto 0);
begin
case shift(1 downto 0) is
when "00" =>
fs1 := frac;
when "01" =>
fs1 := frac(21 downto 0) & '0';
when "10" =>
fs1 := frac(20 downto 0) & "00";
when others =>
fs1 := frac(19 downto 0) & "000";
end case;
case shift(4 downto 2) is
when "000" =>
fs2 := fs1;
when "001" =>
fs2 := fs1(18 downto 0) & x"0" ;
when "010" =>
fs2 := fs1(14 downto 0) & x"00";
when "011" =>
fs2 := fs1(10 downto 0) & x"000";
when "100" =>
fs2 := fs1(6 downto 0) & x"0000";
when others =>
fs2 := fs1(2 downto 0) & x"00000";
end case;
return fs2;
end;
begin
loadstore1_reg: process(clk)
begin
if rising_edge(clk) then
if rst = '1' then
r1.req.valid <= '0';
r2.req.valid <= '0';
r2.wait_dc <= '0';
r2.wait_mmu <= '0';
r2.one_cycle <= '0';
r3.dar <= (others => '0');
r3.dsisr <= (others => '0');
r3.state <= IDLE;
r3.write_enable <= '0';
r3.interrupt <= '0';
r3.stage1_en <= '1';
r3.convert_lfs <= '0';
flushing <= '0';
else
r1 <= r1in;
r2 <= r2in;
r3 <= r3in;
flushing <= (flushing or (r1in.req.valid and r1in.req.align_intr)) and
not r3in.interrupt;
end if;
stage1_dreq <= stage1_dcreq;
if d_in.valid = '1' then
assert r2.req.valid = '1' and r2.req.dc_req = '1' and r3.state = IDLE severity failure;
end if;
if d_in.error = '1' then
assert r2.req.valid = '1' and r2.req.dc_req = '1' and r3.state = IDLE severity failure;
end if;
if m_in.done = '1' or m_in.err = '1' then
assert r2.req.valid = '1' and (r3.state = MMU_LOOKUP or r3.state = TLBIE_WAIT) severity failure;
end if;
end if;
end process;
ls_fp_conv: if HAS_FPU generate
-- Convert DP data to SP for stfs
dp_to_sp: process(all)
variable exp : unsigned(10 downto 0);
variable frac : std_ulogic_vector(22 downto 0);
variable shift : unsigned(4 downto 0);
begin
store_sp_data(31) <= l_in.data(63);
store_sp_data(30 downto 0) <= (others => '0');
exp := unsigned(l_in.data(62 downto 52));
if exp > 896 then
store_sp_data(30) <= l_in.data(62);
store_sp_data(29 downto 0) <= l_in.data(58 downto 29);
elsif exp >= 874 then
-- denormalization required
frac := '1' & l_in.data(51 downto 30);
shift := 0 - exp(4 downto 0);
store_sp_data(22 downto 0) <= shifter_23r(frac, shift);
end if;
end process;
-- Convert SP data to DP for lfs
sp_to_dp: process(all)
variable exp : unsigned(7 downto 0);
variable exp_dp : unsigned(10 downto 0);
variable exp_nz : std_ulogic;
variable exp_ao : std_ulogic;
variable frac : std_ulogic_vector(22 downto 0);
variable frac_shift : unsigned(4 downto 0);
begin
frac := r3.ld_sp_data(22 downto 0);
exp := unsigned(r3.ld_sp_data(30 downto 23));
exp_nz := or (r3.ld_sp_data(30 downto 23));
exp_ao := and (r3.ld_sp_data(30 downto 23));
frac_shift := (others => '0');
if exp_ao = '1' then
exp_dp := to_unsigned(2047, 11); -- infinity or NaN
elsif exp_nz = '1' then
exp_dp := 896 + resize(exp, 11); -- finite normalized value
elsif r3.ld_sp_nz = '0' then
exp_dp := to_unsigned(0, 11); -- zero
else
-- denormalized SP operand, need to normalize
exp_dp := 896 - resize(unsigned(r3.ld_sp_lz), 11);
frac_shift := unsigned(r3.ld_sp_lz(4 downto 0)) + 1;
end if;
load_dp_data(63) <= r3.ld_sp_data(31);
load_dp_data(62 downto 52) <= std_ulogic_vector(exp_dp);
load_dp_data(51 downto 29) <= shifter_23l(frac, frac_shift);
load_dp_data(28 downto 0) <= (others => '0');
end process;
end generate;
-- Translate a load/store instruction into the internal request format
-- XXX this should only depend on l_in, but actually depends on
-- r1.req.addr0 as well (in the l_in.second = 1 case).
loadstore1_in: process(all)
variable v : request_t;
variable lsu_sum : std_ulogic_vector(63 downto 0);
variable brev_lenm1 : unsigned(2 downto 0);
variable long_sel : std_ulogic_vector(15 downto 0);
variable addr : std_ulogic_vector(63 downto 0);
variable sprn : std_ulogic_vector(9 downto 0);
variable misaligned : std_ulogic;
variable addr_mask : std_ulogic_vector(2 downto 0);
begin
v := request_init;
sprn := std_ulogic_vector(to_unsigned(decode_spr_num(l_in.insn), 10));
v.valid := l_in.valid;
v.instr_tag := l_in.instr_tag;
v.mode_32bit := l_in.mode_32bit;
v.write_reg := l_in.write_reg;
v.length := l_in.length;
v.elt_length := l_in.length;
v.byte_reverse := l_in.byte_reverse;
v.sign_extend := l_in.sign_extend;
v.update := l_in.update;
v.xerc := l_in.xerc;
v.reserve := l_in.reserve;
v.rc := l_in.rc;
v.nc := l_in.ci;
v.virt_mode := l_in.virt_mode;
v.priv_mode := l_in.priv_mode;
v.sprn := sprn;
v.nia := l_in.nia;
lsu_sum := std_ulogic_vector(unsigned(l_in.addr1) + unsigned(l_in.addr2));
if HAS_FPU and l_in.is_32bit = '1' then
v.store_data := x"00000000" & store_sp_data;
else
v.store_data := l_in.data;
end if;
addr := lsu_sum;
if l_in.second = '1' then
if l_in.update = '0' then
-- for the second half of a 16-byte transfer,
-- use the previous address plus 8.
addr := std_ulogic_vector(unsigned(r1.req.addr0(63 downto 3)) + 1) & r1.req.addr0(2 downto 0);
else
-- for an update-form load, use the previous address
-- as the value to write back to RA.
addr := r1.req.addr0;
end if;
end if;
if l_in.mode_32bit = '1' then
addr(63 downto 32) := (others => '0');
end if;
v.addr := addr;
v.addr0 := addr;
-- XXX Temporary hack. Mark the op as non-cachable if the address
-- is the form 0xc------- for a real-mode access.
if addr(31 downto 28) = "1100" and l_in.virt_mode = '0' then
v.nc := '1';
end if;
addr_mask := std_ulogic_vector(unsigned(l_in.length(2 downto 0)) - 1);
-- Do length_to_sel and work out if we are doing 2 dwords
long_sel := xfer_data_sel(v.length, addr(2 downto 0));
v.byte_sel := long_sel(7 downto 0);
v.second_bytes := long_sel(15 downto 8);
if long_sel(15 downto 8) /= "00000000" then
v.two_dwords := '1';
end if;
-- check alignment for larx/stcx
misaligned := or (addr_mask and addr(2 downto 0));
v.align_intr := l_in.reserve and misaligned;
if l_in.repeat = '1' and l_in.second = '0' and l_in.update = '0' and addr(3) = '1' then
-- length is really 16 not 8
-- Make misaligned lq cause an alignment interrupt in LE mode,
-- in order to avoid the case with RA = RT + 1 where the second half
-- faults but the first doesn't (and updates RT+1, destroying RA).
-- The equivalent BE case doesn't occur because RA = RT is illegal.
misaligned := '1';
if l_in.reserve = '1' or (l_in.op = OP_LOAD and l_in.byte_reverse = '0') then
v.align_intr := '1';
end if;
end if;
v.atomic := not misaligned;
v.atomic_last := not misaligned and (l_in.second or not l_in.repeat);
case l_in.op is
when OP_STORE =>
v.store := '1';
when OP_LOAD =>
if l_in.update = '0' or l_in.second = '0' then
v.load := '1';
if HAS_FPU and l_in.is_32bit = '1' then
-- Allow an extra cycle for SP->DP precision conversion
v.load_sp := '1';
end if;
else
-- write back address to RA
v.do_update := '1';
end if;
when OP_DCBZ =>
v.dcbz := '1';
v.align_intr := v.nc;
when OP_TLBIE =>
v.tlbie := '1';
v.addr := l_in.addr2; -- address from RB for tlbie
v.is_slbia := l_in.insn(7);
v.mmu_op := '1';
when OP_MFSPR =>
v.read_spr := '1';
when OP_MTSPR =>
v.write_spr := '1';
v.mmu_op := sprn(8) or sprn(5);
when OP_FETCH_FAILED =>
-- send it to the MMU to do the radix walk
v.instr_fault := '1';
v.addr := l_in.nia;
v.mmu_op := '1';
when others =>
end case;
v.dc_req := l_in.valid and (v.load or v.store or v.dcbz) and not v.align_intr;
-- Work out controls for load and store formatting
brev_lenm1 := "000";
if v.byte_reverse = '1' then
brev_lenm1 := unsigned(v.length(2 downto 0)) - 1;
end if;
v.brev_mask := brev_lenm1;
req_in <= v;
end process;
busy <= r1.req.valid and ((r1.req.dc_req and not r1.issued) or
(r1.issued and d_in.error) or
stage2_busy_next or
(r1.req.dc_req and r1.req.two_dwords and not r1.req.dword_index));
complete <= r2.one_cycle or (r2.wait_dc and d_in.valid) or
(r2.wait_mmu and m_in.done) or r3.convert_lfs;
in_progress <= r1.req.valid or (r2.req.valid and not complete);
stage1_issue_enable <= r3.stage1_en and not (r1.req.valid and r1.req.mmu_op) and
not (r2.req.valid and r2.req.mmu_op);
-- Processing done in the first cycle of a load/store instruction
loadstore1_1: process(all)
variable v : reg_stage1_t;
variable req : request_t;
variable dcreq : std_ulogic;
variable addr : std_ulogic_vector(63 downto 0);
begin
v := r1;
dcreq := '0';
req := req_in;
if flushing = '1' then
-- Make this a no-op request rather than simply invalid.
-- It will never get to stage 3 since there is a request ahead of
-- it with align_intr = 1.
req.dc_req := '0';
end if;
-- Note that l_in.valid is gated with busy inside execute1
if l_in.valid = '1' then
dcreq := req.dc_req and stage1_issue_enable and not d_in.error and not dc_stall;
v.req := req;
v.issued := dcreq;
elsif r1.req.valid = '1' then
if r1.req.dc_req = '1' and r1.issued = '0' then
req := r1.req;
dcreq := stage1_issue_enable and not dc_stall and not d_in.error;
v.issued := dcreq;
elsif r1.issued = '1' and d_in.error = '1' then
v.issued := '0';
elsif stage2_busy_next = '0' then
-- we can change what's in r1 next cycle because the current thing
-- in r1 will go into r2
if r1.req.dc_req = '1' and r1.req.two_dwords = '1' and r1.req.dword_index = '0' then
-- construct the second request for a misaligned access
v.req.dword_index := '1';
v.req.addr := std_ulogic_vector(unsigned(r1.req.addr(63 downto 3)) + 1) & "000";
if r1.req.mode_32bit = '1' then
v.req.addr(32) := '0';
end if;
v.req.byte_sel := r1.req.second_bytes;
v.issued := stage1_issue_enable and not dc_stall;
dcreq := stage1_issue_enable and not dc_stall;
req := v.req;
else
v.req.valid := '0';
end if;
end if;
end if;
if r3in.interrupt = '1' then
v.req.valid := '0';
dcreq := '0';
end if;
stage1_req <= req;
stage1_dcreq <= dcreq;
r1in <= v;
end process;
-- Processing done in the second cycle of a load/store instruction.
-- Store data is formatted here and sent to the dcache.
-- The request in r1 is sent to stage 3 if stage 3 will not be busy next cycle.
loadstore1_2: process(all)
variable v : reg_stage2_t;
variable j : integer;
variable k : unsigned(2 downto 0);
variable kk : unsigned(3 downto 0);
variable idx : unsigned(2 downto 0);
variable byte_offset : unsigned(2 downto 0);
begin
v := r2;
-- Byte reversing and rotating for stores.
-- Done in the second cycle (the cycle after l_in.valid = 1).
byte_offset := unsigned(r1.req.addr0(2 downto 0));
for i in 0 to 7 loop
k := (to_unsigned(i, 3) - byte_offset) xor r1.req.brev_mask;
j := to_integer(k) * 8;
store_data(i * 8 + 7 downto i * 8) <= r1.req.store_data(j + 7 downto j);
end loop;
if stage3_busy_next = '0' and
(r1.req.valid = '0' or r1.issued = '1' or r1.req.dc_req = '0') then
v.req := r1.req;
v.req.store_data := store_data;
v.wait_dc := r1.req.valid and r1.req.dc_req and not r1.req.load_sp and
not (r1.req.two_dwords and not r1.req.dword_index);
v.wait_mmu := r1.req.valid and r1.req.mmu_op;
v.one_cycle := r1.req.valid and (r1.req.noop or r1.req.read_spr or
(r1.req.write_spr and not r1.req.mmu_op) or
r1.req.load_zero or r1.req.do_update);
if r1.req.read_spr = '1' then
v.wr_sel := "00";
elsif r1.req.do_update = '1' or r1.req.store = '1' then
v.wr_sel := "01";
elsif r1.req.load_sp = '1' then
v.wr_sel := "10";
else
v.wr_sel := "11";
end if;
-- Work out load formatter controls for next cycle
for i in 0 to 7 loop
idx := to_unsigned(i, 3) xor r1.req.brev_mask;
kk := ('0' & idx) + ('0' & byte_offset);
v.use_second(i) := kk(3);
v.byte_index(i) := kk(2 downto 0);
end loop;
elsif stage3_busy_next = '0' then
v.req.valid := '0';
v.wait_dc := '0';
v.wait_mmu := '0';
end if;
stage2_busy_next <= r1.req.valid and stage3_busy_next;
if r3in.interrupt = '1' then
v.req.valid := '0';
end if;
r2in <= v;
end process;
-- Processing done in the third cycle of a load/store instruction.
-- At this stage we can do things that have side effects without
-- fear of the instruction getting flushed. This is the point at
-- which requests get sent to the MMU.
loadstore1_3: process(all)
variable v : reg_stage3_t;
variable j : integer;
variable req : std_ulogic;
variable mmureq : std_ulogic;
variable mmu_mtspr : std_ulogic;
variable write_enable : std_ulogic;
variable write_data : std_ulogic_vector(63 downto 0);
variable do_update : std_ulogic;
variable done : std_ulogic;
variable part_done : std_ulogic;
variable exception : std_ulogic;
variable data_permuted : std_ulogic_vector(63 downto 0);
variable data_trimmed : std_ulogic_vector(63 downto 0);
variable sprval : std_ulogic_vector(63 downto 0);
variable negative : std_ulogic;
variable dsisr : std_ulogic_vector(31 downto 0);
variable itlb_fault : std_ulogic;
variable trim_ctl : trim_ctl_t;
begin
v := r3;
req := '0';
mmureq := '0';
MMU: Implement radix page table machinery This adds the necessary machinery to the MMU for it to do radix page table walks. The core elements are a shifter that can shift the address right by between 0 and 47 bits, a mask generator that can generate a mask of between 5 and 16 bits, a final mask generator, and new states in the state machine. (The final mask generator is used for transferring bits of the original address into the resulting TLB entry when the leaf PTE corresponds to a page size larger than 4kB.) The hardware does not implement a partition table or a process table. Software is expected to load the appropriate process table entry into a new SPR called PGTBL0, SPR 720. The contents should be formatted as described in Book III section 5.7.6.2 of the Power ISA v3.0B. PGTBL0 is set to 0 on hard reset. At present, the top two bits of the address (the quadrant) are ignored. There is currently no caching of any step in the translation process or of the final result, other than the entry created in the dTLB. That entry is a 4k page entry even if the leaf PTE found in the walk corresponds to a larger page size. This implementation can handle almost any page table layout and any page size. The RTS field (in PGTBL0) can have any value between 0 and 31, corresponding to a total address space size between 2^31 and 2^62 bytes. The RPDS field of PGTBL0 can be any value between 5 and 16, except that a value of 0 is taken to disable radix page table walking (for use when one is using software loading of TLB entries). The NLS field of the page directory entries can have any value between 5 and 16. The minimum page size is 4kB, meaning that the sum of RPDS and the NLS values of the PDEs found on the path to a leaf PTE must be less than or equal to RTS + 31 - 12. The PGTBL0 SPR is in the mmu module; thus this adds a path for loadstore1 to read and write SPRs in mmu. This adds code in dcache to service doubleword read requests from the MMU, as well as requests to write dTLB entries. Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
4 years ago
mmu_mtspr := '0';
done := '0';
part_done := '0';
exception := '0';
dsisr := (others => '0');
write_enable := '0';
sprval := (others => '0');
do_update := '0';
v.convert_lfs := '0';
v.srr1 := (others => '0');
v.events := (others => '0');
-- load data formatting
-- shift and byte-reverse data bytes
for i in 0 to 7 loop
j := to_integer(r2.byte_index(i)) * 8;
data_permuted(i * 8 + 7 downto i * 8) := d_in.data(j + 7 downto j);
end loop;
-- Work out the sign bit for sign extension.
-- For unaligned loads crossing two dwords, the sign bit is in the
-- first dword for big-endian (byte_reverse = 1), or the second dword
-- for little-endian.
if r2.req.dword_index = '1' and r2.req.byte_reverse = '1' then
negative := (r2.req.length(3) and r3.load_data(63)) or
(r2.req.length(2) and r3.load_data(31)) or
(r2.req.length(1) and r3.load_data(15)) or
(r2.req.length(0) and r3.load_data(7));
else
negative := (r2.req.length(3) and data_permuted(63)) or
(r2.req.length(2) and data_permuted(31)) or
(r2.req.length(1) and data_permuted(15)) or
(r2.req.length(0) and data_permuted(7));
end if;
-- trim and sign-extend
for i in 0 to 7 loop
if i < to_integer(unsigned(r2.req.length)) then
if r2.req.dword_index = '1' then
trim_ctl(i) := '1' & not r2.use_second(i);
else
trim_ctl(i) := "10";
end if;
else
trim_ctl(i) := "00";
end if;
end loop;
for i in 0 to 7 loop
case trim_ctl(i) is
when "11" =>
data_trimmed(i * 8 + 7 downto i * 8) := r3.load_data(i * 8 + 7 downto i * 8);
when "10" =>
data_trimmed(i * 8 + 7 downto i * 8) := data_permuted(i * 8 + 7 downto i * 8);
when others =>
data_trimmed(i * 8 + 7 downto i * 8) := (others => negative and r2.req.sign_extend);
end case;
end loop;
if HAS_FPU then
-- Single-precision FP conversion for loads
v.ld_sp_data := data_trimmed(31 downto 0);
v.ld_sp_nz := or (data_trimmed(22 downto 0));
v.ld_sp_lz := count_left_zeroes(data_trimmed(22 downto 0));
end if;
if d_in.valid = '1' and r2.req.load = '1' then
v.load_data := data_permuted;
end if;
if r2.req.valid = '1' then
if r2.req.read_spr = '1' then
write_enable := '1';
-- partial decode on SPR number should be adequate given
-- the restricted set that get sent down this path