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dcache: Implement load-reserve and store-conditional instructions

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This involves plumbing the (existing) 'reserve' and 'rc' bits in
the decode tables down to dcache, and 'rc' and 'store_done' bits
from dcache to writeback.

It turns out that we had 'RC' set in the 'rc' column for several
ordinary stores and for the attn instruction.  This corrects them
to 'NONE', and sets the 'rc' column to 'ONE' for the conditional
stores.

In writeback we now have logic to set CR0 when the input from dcache
has rc = 1.

In dcache we have the reservation itself, which has a valid bit
and the address down to cache line granularity.  We don't currently
store the reservation length.  For a store conditional which fails,
we set a 'cancel_store' signal which inhibits the write to the
cache and prevents the state machine from starting a bus cycle or
going to the STORE_WAIT_ACK state.  Instead we set r1.stcx_fail
which causes the instruction to complete in the next cycle with
rc=1 and store_done=0.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
pull/153/head
Paul Mackerras 5 years ago
parent 94dd8bc480
commit 5d85ede97d
7 changed files with 115 additions and 21 deletions
Show Stats Download Patch File Download Diff File

13
common.vhdl
Unescape Escape View File

@ -130,12 +130,13 @@ package common is
byte_reverse : std_ulogic;
sign_extend : std_ulogic; -- do we need to sign extend?
update : std_ulogic; -- is this an update instruction?
reserve : std_ulogic; -- set for larx/stcx
end record;
constant Decode2ToExecute1Init : Decode2ToExecute1Type :=
(valid => '0', insn_type => OP_ILLEGAL, bypass_data1 => '0', bypass_data2 => '0', bypass_data3 => '0',
lr => '0', rc => '0', oe => '0', invert_a => '0',
invert_out => '0', input_carry => ZERO, output_carry => '0', input_cr => '0', output_cr => '0',
is_32bit => '0', is_signed => '0', xerc => xerc_init,
is_32bit => '0', is_signed => '0', xerc => xerc_init, reserve => '0',
byte_reverse => '0', sign_extend => '0', update => '0', others => (others => '0'));

type Execute1ToMultiplyType is record
@ -206,10 +207,12 @@ package common is
update : std_ulogic; -- is this an update instruction?
update_reg : gpr_index_t; -- if so, the register to update
xerc : xer_common_t;
reserve : std_ulogic; -- set for larx/stcx.
rc : std_ulogic; -- set for stcx.
end record;
constant Execute1ToLoadstore1Init : Execute1ToLoadstore1Type := (valid => '0', load => '0', byte_reverse => '0',
sign_extend => '0', update => '0', xerc => xerc_init,
others => (others => '0'));
reserve => '0', rc => '0', others => (others => '0'));

type Loadstore1ToDcacheType is record
valid : std_ulogic;
@ -224,6 +227,8 @@ package common is
update : std_ulogic;
update_reg : gpr_index_t;
xerc : xer_common_t;
reserve : std_ulogic;
rc : std_ulogic;
end record;

type DcacheToWritebackType is record
@ -237,10 +242,12 @@ package common is
byte_reverse : std_ulogic;
second_word : std_ulogic;
xerc : xer_common_t;
rc : std_ulogic;
store_done : std_ulogic;
end record;
constant DcacheToWritebackInit : DcacheToWritebackType := (valid => '0', write_enable => '0', sign_extend => '0',
byte_reverse => '0', second_word => '0', xerc => xerc_init,
others => (others => '0'));
rc => '0', store_done => '0', others => (others => '0'));

type Execute1ToWritebackType is record
valid: std_ulogic;

78
dcache.vhdl
Unescape Escape View File

@ -171,6 +171,9 @@ architecture rtl of dcache is
slow_data : std_ulogic_vector(63 downto 0);
slow_valid : std_ulogic;

-- Signal to complete a failed stcx.
stcx_fail : std_ulogic;

-- Cache miss state (reload state machine)
state : state_t;
wb : wishbone_master_out;
@ -199,6 +202,15 @@ architecture rtl of dcache is

signal r2 : reg_stage_2_t;

-- Reservation information
--
type reservation_t is record
valid : std_ulogic;
addr : std_ulogic_vector(63 downto LINE_OFF_BITS);
end record;

signal reservation : reservation_t;

-- Async signals on incoming request
signal req_index : index_t;
signal req_row : row_t;
@ -210,6 +222,10 @@ architecture rtl of dcache is
signal req_laddr : std_ulogic_vector(63 downto 0);
signal req_sel : std_ulogic_vector(7 downto 0);

signal cancel_store : std_ulogic;
signal set_rsrv : std_ulogic;
signal clear_rsrv : std_ulogic;

-- Cache RAM interface
type cache_ram_out_t is array(way_t) of cache_row_t;
signal cache_out : cache_ram_out_t;
@ -481,6 +497,41 @@ begin
-- Generate stalls from stage 1 state machine
stall_out <= '1' when r1.state /= IDLE else '0';

-- Handle load-with-reservation and store-conditional instructions
reservation_comb: process(all)
begin
cancel_store <= '0';
set_rsrv <= '0';
clear_rsrv <= '0';
if d_in.valid = '1' and d_in.reserve = '1' then
-- XXX generate alignment interrupt if address is not aligned
-- XXX or if d_in.nc = '1'
if d_in.load = '1' then
-- load with reservation
set_rsrv <= '1';
else
-- store conditional
clear_rsrv <= '1';
if reservation.valid = '0' or
d_in.addr(63 downto LINE_OFF_BITS) /= reservation.addr then
cancel_store <= '1';
end if;
end if;
end if;
end process;

reservation_reg: process(clk)
begin
if rising_edge(clk) then
if rst = '1' or clear_rsrv = '1' then
reservation.valid <= '0';
elsif set_rsrv = '1' then
reservation.valid <= '1';
reservation.addr <= d_in.addr(63 downto LINE_OFF_BITS);
end if;
end if;
end process;

-- Writeback (loads and reg updates) & completion control logic
--
writeback_control: process(all)
@ -497,6 +548,8 @@ begin
d_out.byte_reverse <= r2.byte_reverse;
d_out.second_word <= r2.second_dword;
d_out.xerc <= r2.xerc;
d_out.rc <= '0'; -- loads never have rc=1
d_out.store_done <= '0';

-- We have a valid load or store hit or we just completed a slow
-- op such as a load miss, a NC load or a store
@ -512,11 +565,14 @@ begin
assert (r1.update_valid and r2.hit_load_valid) /= '1' report
"unexpected hit_load_delayed collision with update_valid"
severity FAILURE;
assert (r1.slow_valid and r2.hit_load_valid) /= '1' report
assert (r1.slow_valid and r1.stcx_fail) /= '1' report
"unexpected slow_valid collision with stcx_fail"
severity FAILURE;
assert ((r1.slow_valid or r1.stcx_fail) and r2.hit_load_valid) /= '1' report
"unexpected hit_load_delayed collision with slow_valid"
severity FAILURE;
assert (r1.slow_valid and r1.update_valid) /= '1' report
"unexpected update_valid collision with slow_valid"
assert ((r1.slow_valid or r1.stcx_fail) and r1.update_valid) /= '1' report
"unexpected update_valid collision with slow_valid or stcx_fail"
severity FAILURE;

-- Delayed load hit case is the standard path
@ -551,6 +607,8 @@ begin
d_out.xerc <= r1.req.xerc;
d_out.second_word <= r1.second_dword;
end if;
d_out.rc <= r1.req.rc;
d_out.store_done <= '1';

-- If it's a store or a non-update load form, complete now
-- unless we need to do another dword transfer
@ -561,6 +619,12 @@ begin
end if;
end if;

if r1.stcx_fail = '1' then
d_out.rc <= r1.req.rc;
d_out.store_done <= '0';
d_out.valid <= '1';
end if;

-- We have a register update to do.
if r1.update_valid = '1' then
d_out.write_enable <= '1';
@ -657,7 +721,7 @@ begin
if reloading and wishbone_in.ack = '1' and r1.store_way = i then
do_write <= '1';
end if;
if req_op = OP_STORE_HIT and req_hit_way = i then
if req_op = OP_STORE_HIT and req_hit_way = i and cancel_store = '0' then
assert not reloading report "Store hit while in state:" &
state_t'image(r1.state)
severity FAILURE;
@ -753,6 +817,7 @@ begin
-- One cycle pulses reset
r1.slow_valid <= '0';
r1.update_valid <= '0';
r1.stcx_fail <= '0';

-- We cannot currently process a new request when not idle
assert d_in.valid = '0' or r1.state = IDLE report "request " &
@ -832,10 +897,15 @@ begin
r1.wb.sel <= req_sel;
r1.wb.adr <= req_addr(r1.wb.adr'left downto 3) & "000";
r1.wb.dat <= req_data;
if cancel_store = '0' then
r1.wb.cyc <= '1';
r1.wb.stb <= '1';
r1.wb.we <= '1';
r1.state <= STORE_WAIT_ACK;
else
r1.stcx_fail <= '1';
r1.state <= IDLE;
end if;

-- OP_NONE and OP_BAD do nothing
when OP_NONE =>

18
decode1.vhdl
Unescape Escape View File

@ -60,8 +60,8 @@ architecture behaviour of decode1 is
20 => (ALU, OP_RLC, RA, CONST_SH32, RS, RA, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '0', RC, '0', '0'), -- rlwimi
21 => (ALU, OP_RLC, NONE, CONST_SH32, RS, RA, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '0', RC, '0', '0'), -- rlwinm
23 => (ALU, OP_RLC, NONE, RB, RS, RA, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '0', RC, '0', '0'), -- rlwnm
38 => (LDST, OP_STORE, RA_OR_ZERO, CONST_SI, RS, NONE, '0', '0', '0', '0', ZERO, '0', is1B, '0', '0', '0', '0', '0', '0', RC, '0', '0'), -- stb
39 => (LDST, OP_STORE, RA_OR_ZERO, CONST_SI, RS, NONE, '0', '0', '0', '0', ZERO, '0', is1B, '0', '0', '1', '0', '0', '0', RC, '0', '0'), -- stbu
38 => (LDST, OP_STORE, RA_OR_ZERO, CONST_SI, RS, NONE, '0', '0', '0', '0', ZERO, '0', is1B, '0', '0', '0', '0', '0', '0', NONE, '0', '0'), -- stb
39 => (LDST, OP_STORE, RA_OR_ZERO, CONST_SI, RS, NONE, '0', '0', '0', '0', ZERO, '0', is1B, '0', '0', '1', '0', '0', '0', NONE, '0', '0'), -- stbu
44 => (LDST, OP_STORE, RA_OR_ZERO, CONST_SI, RS, NONE, '0', '0', '0', '0', ZERO, '0', is2B, '0', '0', '0', '0', '0', '0', NONE, '0', '0'), -- sth
45 => (LDST, OP_STORE, RA_OR_ZERO, CONST_SI, RS, NONE, '0', '0', '0', '0', ZERO, '0', is2B, '0', '0', '1', '0', '0', '0', NONE, '0', '0'), -- sthu
36 => (LDST, OP_STORE, RA_OR_ZERO, CONST_SI, RS, NONE, '0', '0', '0', '0', ZERO, '0', is4B, '0', '0', '0', '0', '0', '0', NONE, '0', '0'), -- stw
@ -278,19 +278,19 @@ architecture behaviour of decode1 is
2#1100111000# => (ALU, OP_SHR, NONE, CONST_SH32, RS, RA, '0', '0', '0', '0', ZERO, '1', NONE, '0', '0', '0', '0', '1', '1', RC, '0', '0'), -- srawi
2#1000011011# => (ALU, OP_SHR, NONE, RB, RS, RA, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC, '0', '0'), -- srd
2#1000011000# => (ALU, OP_SHR, NONE, RB, RS, RA, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '1', '0', RC, '0', '0'), -- srw
2#1010110110# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is1B, '0', '0', '0', '1', '0', '0', RC, '0', '0'), -- stbcx
2#0011110111# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is1B, '0', '0', '1', '0', '0', '0', RC, '0', '0'), -- stbux
2#0011010111# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is1B, '0', '0', '0', '0', '0', '0', RC, '0', '0'), -- stbx
2#1010110110# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is1B, '0', '0', '0', '1', '0', '0', ONE, '0', '0'), -- stbcx
2#0011110111# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is1B, '0', '0', '1', '0', '0', '0', NONE, '0', '0'), -- stbux
2#0011010111# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is1B, '0', '0', '0', '0', '0', '0', NONE, '0', '0'), -- stbx
2#1010010100# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is8B, '1', '0', '0', '0', '0', '0', NONE, '0', '0'), -- stdbrx
2#0011010110# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is8B, '0', '0', '0', '1', '0', '0', NONE, '0', '0'), -- stdcx
2#0011010110# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is8B, '0', '0', '0', '1', '0', '0', ONE, '0', '0'), -- stdcx
2#0010110101# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is8B, '0', '0', '1', '0', '0', '0', NONE, '0', '0'), -- stdux
2#0010010101# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is8B, '0', '0', '0', '0', '0', '0', NONE, '0', '0'), -- stdx
2#1110010110# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is2B, '1', '0', '0', '0', '0', '0', NONE, '0', '0'), -- sthbrx
2#1011010110# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is2B, '0', '0', '0', '1', '0', '0', NONE, '0', '0'), -- sthcx
2#1011010110# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is2B, '0', '0', '0', '1', '0', '0', ONE, '0', '0'), -- sthcx
2#0110110111# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is2B, '0', '0', '1', '0', '0', '0', NONE, '0', '0'), -- sthux
2#0110010111# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is2B, '0', '0', '0', '0', '0', '0', NONE, '0', '0'), -- sthx
2#1010010110# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is4B, '1', '0', '0', '0', '0', '0', NONE, '0', '0'), -- stwbrx
2#0010010110# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is4B, '0', '0', '0', '1', '0', '0', NONE, '0', '0'), -- stwcx
2#0010010110# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is4B, '0', '0', '0', '1', '0', '0', ONE, '0', '0'), -- stwcx
2#0010110111# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is4B, '0', '0', '1', '0', '0', '0', NONE, '0', '0'), -- stwux
2#0010010111# => (LDST, OP_STORE, RA_OR_ZERO, RB, RS, NONE, '0', '0', '0', '0', ZERO, '0', is4B, '0', '0', '0', '0', '0', '0', NONE, '0', '0'), -- stwx
2#0000101000# => (ALU, OP_ADD, RA, RB, NONE, RT, '0', '0', '1', '0', ONE, '0', NONE, '0', '0', '0', '0', '0', '0', RC, '0', '0'), -- subf
@ -329,7 +329,7 @@ architecture behaviour of decode1 is

-- unit internal in1 in2 in3 out CR CR inv inv cry cry ldst BR sgn upd rsrv 32b sgn rc lk sgl
-- op in out A out in out len ext pipe
constant attn_instr : decode_rom_t := (ALU, OP_ILLEGAL, NONE, NONE, NONE, NONE, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', RC, '0', '1');
constant attn_instr : decode_rom_t := (ALU, OP_ILLEGAL, NONE, NONE, NONE, NONE, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0', '1');
constant nop_instr : decode_rom_t := (ALU, OP_NOP, NONE, NONE, NONE, NONE, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0', '0');
constant sim_cfg_instr : decode_rom_t := (ALU, OP_SIM_CONFIG,NONE, NONE, NONE, RT, '0', '0', '0', '0', ZERO, '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0', '1');


1
decode2.vhdl
Unescape Escape View File

@ -334,6 +334,7 @@ begin
v.e.byte_reverse := d_in.decode.byte_reverse;
v.e.sign_extend := d_in.decode.sign_extend;
v.e.update := d_in.decode.update;
v.e.reserve := d_in.decode.reserve;

-- issue control
control_valid_in <= d_in.valid;

2
execute1.vhdl
Unescape Escape View File

@ -759,6 +759,8 @@ begin
lv.update := e_in.update;
lv.update_reg := gspr_to_gpr(e_in.read_reg1);
lv.xerc := v.e.xerc;
lv.reserve := e_in.reserve;
lv.rc := e_in.rc;

-- Update registers
rin <= v;

2
loadstore1.vhdl
Unescape Escape View File

@ -51,6 +51,8 @@ begin
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;

-- XXX Temporary hack. Mark the op as non-cachable if the address
-- is the form 0xc-------

12
writeback.vhdl
Unescape Escape View File

@ -63,6 +63,7 @@ begin
variable xe: xer_common_t;
variable zero : std_ulogic;
variable sign : std_ulogic;
variable scf : std_ulogic_vector(3 downto 0);
begin
x(0) := e_in.valid;
y(0) := l_in.valid;
@ -124,6 +125,17 @@ begin
w_out.write_enable <= not partial_write or second_word;
end if;

if l_in.rc = '1' then
-- st*cx. instructions
scf(3) := '0';
scf(2) := '0';
scf(1) := l_in.store_done;
scf(0) := xe.so;
c_out.write_cr_enable <= '1';
c_out.write_cr_mask <= num_to_fxm(0);
c_out.write_cr_data(31 downto 28) <= scf;
end if;

-- shift and byte-reverse data bytes
for i in 0 to 7 loop
k := ('0' & (to_unsigned(i, 3) xor brev_lenm1)) + ('0' & byte_offset);

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