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microwatt/loadstore1.vhdl

579 lines
21 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;
-- 2 cycle LSU
-- We calculate the address in the first cycle
entity loadstore1 is
generic (
-- 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;
log_out : out std_ulogic_vector(9 downto 0)
);
end loadstore1;
-- Note, we don't currently use the stall output from the dcache because
-- we know it can take two requests without stalling when idle, we are
-- its only user, and we know it never stalls when idle.
architecture behave of loadstore1 is
-- State machine for unaligned loads/stores
type state_t is (IDLE, -- ready for instruction
SECOND_REQ, -- send 2nd request of unaligned xfer
ACK_WAIT, -- waiting for ack from dcache
MMU_LOOKUP, -- waiting for MMU to look up translation
TLBIE_WAIT, -- waiting for MMU to finish doing a tlbie
COMPLETE -- extra cycle to complete an operation
);
type reg_stage_t is record
-- latch most of the input request
load : std_ulogic;
tlbie : std_ulogic;
dcbz : std_ulogic;
mfspr : std_ulogic;
addr : std_ulogic_vector(63 downto 0);
store_data : std_ulogic_vector(63 downto 0);
load_data : std_ulogic_vector(63 downto 0);
write_reg : gpr_index_t;
length : std_ulogic_vector(3 downto 0);
byte_reverse : std_ulogic;
sign_extend : std_ulogic;
update : std_ulogic;
update_reg : gpr_index_t;
xerc : xer_common_t;
reserve : std_ulogic;
rc : std_ulogic;
nc : std_ulogic; -- non-cacheable access
virt_mode : std_ulogic;
priv_mode : std_ulogic;
state : state_t;
dwords_done : std_ulogic;
last_dword : std_ulogic;
first_bytes : std_ulogic_vector(7 downto 0);
second_bytes : std_ulogic_vector(7 downto 0);
dar : std_ulogic_vector(63 downto 0);
dsisr : std_ulogic_vector(31 downto 0);
instr_fault : std_ulogic;
align_intr : std_ulogic;
sprval : std_ulogic_vector(63 downto 0);
busy : std_ulogic;
wait_dcache : std_ulogic;
wait_mmu : std_ulogic;
do_update : std_ulogic;
extra_cycle : std_ulogic;
mode_32bit : std_ulogic;
end record;
type byte_sel_t is array(0 to 7) of std_ulogic;
subtype byte_trim_t is std_ulogic_vector(1 downto 0);
type trim_ctl_t is array(0 to 7) of byte_trim_t;
signal r, rin : reg_stage_t;
signal lsu_sum : std_ulogic_vector(63 downto 0);
-- 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;
begin
-- Calculate the address in the first cycle
lsu_sum <= std_ulogic_vector(unsigned(l_in.addr1) + unsigned(l_in.addr2)) when l_in.valid = '1' else (others => '0');
loadstore1_0: process(clk)
begin
if rising_edge(clk) then
if rst = '1' then
r.state <= IDLE;
r.busy <= '0';
r.do_update <= '0';
else
r <= rin;
end if;
end if;
end process;
loadstore1_1: process(all)
variable v : reg_stage_t;
variable brev_lenm1 : unsigned(2 downto 0);
variable byte_offset : unsigned(2 downto 0);
variable j : integer;
variable k : unsigned(2 downto 0);
variable kk : unsigned(3 downto 0);
variable long_sel : std_ulogic_vector(15 downto 0);
variable byte_sel : std_ulogic_vector(7 downto 0);
variable req : std_ulogic;
variable busy : std_ulogic;
variable addr : std_ulogic_vector(63 downto 0);
variable maddr : std_ulogic_vector(63 downto 0);
variable wdata : std_ulogic_vector(63 downto 0);
variable write_enable : std_ulogic;
variable do_update : std_ulogic;
variable done : std_ulogic;
variable data_permuted : std_ulogic_vector(63 downto 0);
variable data_trimmed : std_ulogic_vector(63 downto 0);
variable store_data : std_ulogic_vector(63 downto 0);
variable use_second : byte_sel_t;
variable trim_ctl : trim_ctl_t;
variable negative : std_ulogic;
variable sprn : std_ulogic_vector(9 downto 0);
variable exception : std_ulogic;
variable next_addr : std_ulogic_vector(63 downto 0);
variable mmureq : std_ulogic;
variable dsisr : std_ulogic_vector(31 downto 0);
variable mmu_mtspr : std_ulogic;
variable itlb_fault : std_ulogic;
variable misaligned : std_ulogic;
begin
v := r;
req := '0';
v.mfspr := '0';
mmu_mtspr := '0';
itlb_fault := '0';
sprn := std_ulogic_vector(to_unsigned(decode_spr_num(l_in.insn), 10));
dsisr := (others => '0');
mmureq := '0';
write_enable := '0';
do_update := r.do_update;
v.do_update := '0';
-- load data formatting
byte_offset := unsigned(r.addr(2 downto 0));
brev_lenm1 := "000";
if r.byte_reverse = '1' then
brev_lenm1 := unsigned(r.length(2 downto 0)) - 1;
end if;
-- shift and byte-reverse data bytes
for i in 0 to 7 loop
kk := ('0' & (to_unsigned(i, 3) xor brev_lenm1)) + ('0' & byte_offset);
use_second(i) := kk(3);
j := to_integer(kk(2 downto 0)) * 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 r.dwords_done = '1' and r.byte_reverse = '1' then
negative := (r.length(3) and r.load_data(63)) or
(r.length(2) and r.load_data(31)) or
(r.length(1) and r.load_data(15)) or
(r.length(0) and r.load_data(7));
else
negative := (r.length(3) and data_permuted(63)) or
(r.length(2) and data_permuted(31)) or
(r.length(1) and data_permuted(15)) or
(r.length(0) and data_permuted(7));
end if;
-- trim and sign-extend
for i in 0 to 7 loop
if i < to_integer(unsigned(r.length)) then
if r.dwords_done = '1' then
trim_ctl(i) := '1' & not use_second(i);
else
trim_ctl(i) := "10";
end if;
else
trim_ctl(i) := '0' & (negative and r.sign_extend);
end if;
case trim_ctl(i) is
when "11" =>
data_trimmed(i * 8 + 7 downto i * 8) := r.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 "01" =>
data_trimmed(i * 8 + 7 downto i * 8) := x"FF";
when others =>
data_trimmed(i * 8 + 7 downto i * 8) := x"00";
end case;
end loop;
-- Byte reversing and rotating for stores
-- Done in the first cycle (when l_in.valid = 1)
store_data := r.store_data;
if l_in.valid = '1' then
byte_offset := unsigned(lsu_sum(2 downto 0));
brev_lenm1 := "000";
if l_in.byte_reverse = '1' then
brev_lenm1 := unsigned(l_in.length(2 downto 0)) - 1;
end if;
for i in 0 to 7 loop
k := (to_unsigned(i, 3) - byte_offset) xor brev_lenm1;
j := to_integer(k) * 8;
store_data(i * 8 + 7 downto i * 8) := l_in.data(j + 7 downto j);
end loop;
end if;
v.store_data := store_data;
-- compute (addr + 8) & ~7 for the second doubleword when unaligned
next_addr := std_ulogic_vector(unsigned(r.addr(63 downto 3)) + 1) & "000";
-- Busy calculation.
-- We need to minimize the delay from clock to busy valid because it
-- gates the start of execution of the next instruction.
busy := r.busy and not ((r.wait_dcache and d_in.valid) or (r.wait_mmu and m_in.done));
v.busy := busy;
done := '0';
if r.state /= IDLE and busy = '0' then
done := '1';
end if;
exception := '0';
if r.dwords_done = '1' or r.state = SECOND_REQ then
addr := next_addr;
byte_sel := r.second_bytes;
else
addr := r.addr;
byte_sel := r.first_bytes;
end if;
if r.mode_32bit = '1' then
addr(63 downto 32) := (others => '0');
end if;
maddr := addr;
case r.state is
when IDLE =>
when SECOND_REQ =>
req := '1';
v.state := ACK_WAIT;
v.last_dword := '0';
when ACK_WAIT =>
if d_in.error = '1' then
-- dcache will discard the second request if it
-- gets an error on the 1st of two requests
if d_in.cache_paradox = '1' then
-- signal an interrupt straight away
exception := '1';
dsisr(63 - 38) := not r.load;
-- XXX there is no architected bit for this
dsisr(63 - 35) := d_in.cache_paradox;
else
-- Look up the translation for TLB miss
-- and also for permission error and RC error
-- in case the PTE has been updated.
mmureq := '1';
v.state := MMU_LOOKUP;
end if;
end if;
if d_in.valid = '1' then
if r.last_dword = '0' then
v.dwords_done := '1';
v.last_dword := '1';
if r.load = '1' then
v.load_data := data_permuted;
end if;
else
write_enable := r.load;
if r.extra_cycle = '1' then
-- loads with rA update need an extra cycle
v.state := COMPLETE;
v.do_update := r.update;
else
-- stores write back rA update in this cycle
do_update := r.update;
end if;
v.busy := '0';
end if;
end if;
-- r.wait_dcache gets set one cycle after we come into ACK_WAIT state,
-- which is OK because the dcache always takes at least two cycles.
v.wait_dcache := r.last_dword and not r.extra_cycle;
when MMU_LOOKUP =>
if m_in.done = '1' then
if r.instr_fault = '0' then
-- retry the request now that the MMU has installed a TLB entry
req := '1';
if r.last_dword = '0' then
v.state := SECOND_REQ;
else
v.state := ACK_WAIT;
end if;
end if;
end if;
if m_in.err = '1' then
exception := '1';
dsisr(63 - 33) := m_in.invalid;
dsisr(63 - 36) := m_in.perm_error;
dsisr(63 - 38) := not r.load;
dsisr(63 - 44) := m_in.badtree;
dsisr(63 - 45) := m_in.rc_error;
end if;
when TLBIE_WAIT =>
when COMPLETE =>
exception := r.align_intr;
end case;
if done = '1' or exception = '1' then
v.state := IDLE;
v.busy := '0';
end if;
-- Note that l_in.valid is gated with busy inside execute1
if l_in.valid = '1' then
v.addr := lsu_sum;
v.mode_32bit := l_in.mode_32bit;
v.load := '0';
v.dcbz := '0';
v.tlbie := '0';
v.instr_fault := '0';
v.align_intr := '0';
v.dwords_done := '0';
v.last_dword := '1';
v.write_reg := l_in.write_reg;
v.length := l_in.length;
v.byte_reverse := l_in.byte_reverse;
v.sign_extend := l_in.sign_extend;
v.update := l_in.update;
v.update_reg := l_in.update_reg;
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.wait_dcache := '0';
v.wait_mmu := '0';
v.do_update := '0';
v.extra_cycle := '0';
addr := lsu_sum;
if l_in.mode_32bit = '1' then
addr(63 downto 32) := (others => '0');
end if;
maddr := l_in.addr2; -- address from RB for tlbie
-- XXX Temporary hack. Mark the op as non-cachable if the address
-- is the form 0xc------- for a real-mode access.
if lsu_sum(31 downto 28) = "1100" and l_in.virt_mode = '0' then
v.nc := '1';
end if;
-- Do length_to_sel and work out if we are doing 2 dwords
long_sel := xfer_data_sel(l_in.length, v.addr(2 downto 0));
byte_sel := long_sel(7 downto 0);
v.first_bytes := byte_sel;
v.second_bytes := long_sel(15 downto 8);
-- check alignment for larx/stcx
misaligned := or (std_ulogic_vector(unsigned(l_in.length(2 downto 0)) - 1) and addr(2 downto 0));
v.align_intr := l_in.reserve and misaligned;
case l_in.op is
when OP_STORE =>
req := '1';
when OP_LOAD =>
req := '1';
v.load := '1';
-- Allow an extra cycle for RA update on loads
v.extra_cycle := l_in.update;
when OP_DCBZ =>
v.align_intr := v.nc;
req := '1';
v.dcbz := '1';
when OP_TLBIE =>
mmureq := '1';
v.tlbie := '1';
v.state := TLBIE_WAIT;
v.wait_mmu := '1';
when OP_MFSPR =>
v.mfspr := '1';
-- partial decode on SPR number should be adequate given
-- the restricted set that get sent down this path
if sprn(9) = '0' and sprn(5) = '0' then
if sprn(0) = '0' then
v.sprval := x"00000000" & r.dsisr;
else
v.sprval := r.dar;
end if;
else
-- reading one of the SPRs in the MMU
v.sprval := m_in.sprval;
end if;
v.state := COMPLETE;
when OP_MTSPR =>
if sprn(9) = '0' and sprn(5) = '0' then
if sprn(0) = '0' then
v.dsisr := l_in.data(31 downto 0);
else
v.dar := l_in.data;
end if;
v.state := COMPLETE;
else
-- writing one of the SPRs in the MMU
mmu_mtspr := '1';
v.state := TLBIE_WAIT;
v.wait_mmu := '1';
end if;
when OP_FETCH_FAILED =>
-- send it to the MMU to do the radix walk
maddr := l_in.nia;
v.instr_fault := '1';
mmureq := '1';
v.state := MMU_LOOKUP;
v.wait_mmu := '1';
when others =>
assert false report "unknown op sent to loadstore1";
end case;
if req = '1' then
if v.align_intr = '1' then
v.state := COMPLETE;
elsif long_sel(15 downto 8) = "00000000" then
v.state := ACK_WAIT;
else
v.state := SECOND_REQ;
end if;
end if;
v.busy := req or mmureq or mmu_mtspr;
end if;
-- Update outputs to dcache
d_out.valid <= req and not v.align_intr;
d_out.load <= v.load;
d_out.dcbz <= v.dcbz;
d_out.nc <= v.nc;
d_out.reserve <= v.reserve;
d_out.addr <= addr;
d_out.data <= store_data;
d_out.byte_sel <= byte_sel;
d_out.virt_mode <= v.virt_mode;
d_out.priv_mode <= v.priv_mode;
-- Update outputs to MMU
m_out.valid <= mmureq;
m_out.iside <= v.instr_fault;
m_out.load <= r.load;
m_out.priv <= r.priv_mode;
m_out.tlbie <= v.tlbie;
m_out.mtspr <= mmu_mtspr;
m_out.sprn <= sprn;
m_out.addr <= maddr;
m_out.slbia <= l_in.insn(7);
m_out.rs <= l_in.data;
-- Update outputs to writeback
-- Multiplex either cache data to the destination GPR or
-- the address for the rA update.
l_out.valid <= done;
if r.mfspr = '1' then
l_out.write_enable <= '1';
l_out.write_reg <= r.write_reg;
l_out.write_data <= r.sprval;
elsif do_update = '1' then
l_out.write_enable <= '1';
l_out.write_reg <= r.update_reg;
l_out.write_data <= r.addr;
else
l_out.write_enable <= write_enable;
l_out.write_reg <= r.write_reg;
l_out.write_data <= data_trimmed;
end if;
l_out.xerc <= r.xerc;
l_out.rc <= r.rc and done;
l_out.store_done <= d_in.store_done;
-- update exception info back to execute1
e_out.busy <= busy;
e_out.exception <= exception;
e_out.alignment <= r.align_intr;
e_out.instr_fault <= r.instr_fault;
e_out.invalid <= m_in.invalid;
e_out.badtree <= m_in.badtree;
e_out.perm_error <= m_in.perm_error;
e_out.rc_error <= m_in.rc_error;
e_out.segment_fault <= m_in.segerr;
if exception = '1' and r.instr_fault = '0' then
v.dar := addr;
if m_in.segerr = '0' and r.align_intr = '0' then
v.dsisr := dsisr;
end if;
end if;
-- Update registers
rin <= v;
end process;
l1_log: if LOG_LENGTH > 0 generate
signal log_data : std_ulogic_vector(9 downto 0);
begin
ls1_log: process(clk)
begin
if rising_edge(clk) then
log_data <= e_out.busy &
e_out.exception &
l_out.valid &
m_out.valid &
d_out.valid &
m_in.done &
r.dwords_done &
std_ulogic_vector(to_unsigned(state_t'pos(r.state), 3));
end if;
end process;
log_out <= log_data;
end generate;
end;