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A tiny Open POWER ISA softcore written in VHDL 2008
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microwatt/core_debug.vhdl

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library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
library work;
use work.utils.all;
use work.common.all;
entity core_debug is
generic (
-- Length of log buffer
LOG_LENGTH : natural := 512
);
port (
clk : in std_logic;
rst : in std_logic;
dmi_addr : in std_ulogic_vector(3 downto 0);
dmi_din : in std_ulogic_vector(63 downto 0);
dmi_dout : out std_ulogic_vector(63 downto 0);
dmi_req : in std_ulogic;
dmi_wr : in std_ulogic;
dmi_ack : out std_ulogic;
-- Debug actions
core_stop : out std_ulogic;
core_rst : out std_ulogic;
icache_rst : out std_ulogic;
-- Core status inputs
terminate : in std_ulogic;
core_stopped : in std_ulogic;
nia : in std_ulogic_vector(63 downto 0);
msr : in std_ulogic_vector(63 downto 0);
-- GPR/FPR register read port
dbg_gpr_req : out std_ulogic;
dbg_gpr_ack : in std_ulogic;
dbg_gpr_addr : out gspr_index_t;
dbg_gpr_data : in std_ulogic_vector(63 downto 0);
-- SPR register read port for SPRs in execute1
dbg_spr_req : out std_ulogic;
dbg_spr_ack : in std_ulogic;
dbg_spr_addr : out std_ulogic_vector(7 downto 0);
dbg_spr_data : in std_ulogic_vector(63 downto 0);
-- SPR register read port for SPRs in loadstore1 and mmu
dbg_ls_spr_req : out std_ulogic;
dbg_ls_spr_ack : in std_ulogic;
dbg_ls_spr_addr : out std_ulogic_vector(1 downto 0);
dbg_ls_spr_data : in std_ulogic_vector(63 downto 0);
-- Core logging data
log_data : in std_ulogic_vector(255 downto 0);
log_read_addr : in std_ulogic_vector(31 downto 0);
log_read_data : out std_ulogic_vector(63 downto 0);
log_write_addr : out std_ulogic_vector(31 downto 0);
-- Misc
terminated_out : out std_ulogic
);
end core_debug;
architecture behave of core_debug is
-- DMI needs fixing... make a one clock pulse
signal dmi_req_1: std_ulogic;
-- CTRL register (direct actions, write 1 to act, read back 0)
-- bit 0 : Core stop
-- bit 1 : Core reset (doesn't clear stop)
-- bit 2 : Icache reset
-- bit 3 : Single step
-- bit 4 : Core start
constant DBG_CORE_CTRL : std_ulogic_vector(3 downto 0) := "0000";
constant DBG_CORE_CTRL_STOP : integer := 0;
constant DBG_CORE_CTRL_RESET : integer := 1;
constant DBG_CORE_CTRL_ICRESET : integer := 2;
constant DBG_CORE_CTRL_STEP : integer := 3;
constant DBG_CORE_CTRL_START : integer := 4;
-- STAT register (read only)
-- bit 0 : Core stopping (wait til bit 1 set)
-- bit 1 : Core stopped
-- bit 2 : Core terminated (clears with start or reset)
constant DBG_CORE_STAT : std_ulogic_vector(3 downto 0) := "0001";
constant DBG_CORE_STAT_STOPPING : integer := 0;
constant DBG_CORE_STAT_STOPPED : integer := 1;
constant DBG_CORE_STAT_TERM : integer := 2;
-- NIA register (read only for now)
constant DBG_CORE_NIA : std_ulogic_vector(3 downto 0) := "0010";
-- MSR (read only)
constant DBG_CORE_MSR : std_ulogic_vector(3 downto 0) := "0011";
-- GSPR register index
constant DBG_CORE_GSPR_INDEX : std_ulogic_vector(3 downto 0) := "0100";
-- GSPR register data
constant DBG_CORE_GSPR_DATA : std_ulogic_vector(3 downto 0) := "0101";
-- Log buffer address and data registers
constant DBG_CORE_LOG_ADDR : std_ulogic_vector(3 downto 0) := "0110";
constant DBG_CORE_LOG_DATA : std_ulogic_vector(3 downto 0) := "0111";
constant DBG_CORE_LOG_TRIGGER : std_ulogic_vector(3 downto 0) := "1000";
constant LOG_INDEX_BITS : natural := log2(LOG_LENGTH);
-- Some internal wires
signal stat_reg : std_ulogic_vector(63 downto 0);
-- Some internal latches
signal stopping : std_ulogic;
signal do_step : std_ulogic;
signal do_reset : std_ulogic;
signal do_icreset : std_ulogic;
signal terminated : std_ulogic;
signal do_gspr_rd : std_ulogic;
signal gspr_index : std_ulogic_vector(7 downto 0);
signal gspr_data : std_ulogic_vector(63 downto 0);
signal spr_index_valid : std_ulogic;
signal log_dmi_addr : std_ulogic_vector(31 downto 0) := (others => '0');
signal log_dmi_data : std_ulogic_vector(63 downto 0) := (others => '0');
signal log_dmi_trigger : std_ulogic_vector(63 downto 0) := (others => '0');
signal do_log_trigger : std_ulogic := '0';
signal do_dmi_log_rd : std_ulogic;
signal dmi_read_log_data : std_ulogic;
signal dmi_read_log_data_1 : std_ulogic;
signal log_trigger_delay : integer range 0 to 255 := 0;
begin
-- Single cycle register accesses on DMI except for GSPR data
dmi_ack <= dmi_req when dmi_addr /= DBG_CORE_GSPR_DATA
else dbg_gpr_ack or dbg_spr_ack or dbg_ls_spr_ack;
-- Status register read composition
stat_reg <= (2 => terminated,
1 => core_stopped,
0 => stopping,
others => '0');
gspr_data <= dbg_gpr_data when gspr_index(5) = '0' else
dbg_ls_spr_data when dbg_ls_spr_req = '1' else
dbg_spr_data when spr_index_valid = '1' else
(others => '0');
-- DMI read data mux
with dmi_addr select dmi_dout <=
stat_reg when DBG_CORE_STAT,
nia when DBG_CORE_NIA,
msr when DBG_CORE_MSR,
gspr_data when DBG_CORE_GSPR_DATA,
log_write_addr & log_dmi_addr when DBG_CORE_LOG_ADDR,
log_dmi_data when DBG_CORE_LOG_DATA,
log_dmi_trigger when DBG_CORE_LOG_TRIGGER,
(others => '0') when others;
-- DMI writes
reg_write: process(clk)
begin
if rising_edge(clk) then
-- Reset the 1-cycle "do" signals
do_step <= '0';
do_reset <= '0';
do_icreset <= '0';
do_dmi_log_rd <= '0';
if (rst) then
stopping <= '0';
terminated <= '0';
log_trigger_delay <= 0;
gspr_index <= (others => '0');
log_dmi_addr <= (others => '0');
else
if do_log_trigger = '1' or log_trigger_delay /= 0 then
if log_trigger_delay = 255 or
(LOG_LENGTH < 1024 and log_trigger_delay = LOG_LENGTH / 4) then
log_dmi_trigger(1) <= '1';
log_trigger_delay <= 0;
else
log_trigger_delay <= log_trigger_delay + 1;
end if;
end if;
-- Edge detect on dmi_req for 1-shot pulses
dmi_req_1 <= dmi_req;
if dmi_req = '1' and dmi_req_1 = '0' then
if dmi_wr = '1' then
report("DMI write to " & to_hstring(dmi_addr));
-- Control register actions
if dmi_addr = DBG_CORE_CTRL then
if dmi_din(DBG_CORE_CTRL_RESET) = '1' then
do_reset <= '1';
terminated <= '0';
end if;
if dmi_din(DBG_CORE_CTRL_STOP) = '1' then
stopping <= '1';
end if;
if dmi_din(DBG_CORE_CTRL_STEP) = '1' then
do_step <= '1';
terminated <= '0';
end if;
if dmi_din(DBG_CORE_CTRL_ICRESET) = '1' then
do_icreset <= '1';
end if;
if dmi_din(DBG_CORE_CTRL_START) = '1' then
stopping <= '0';
terminated <= '0';
end if;
elsif dmi_addr = DBG_CORE_GSPR_INDEX then
gspr_index <= dmi_din(7 downto 0);
elsif dmi_addr = DBG_CORE_LOG_ADDR then
log_dmi_addr <= dmi_din(31 downto 0);
do_dmi_log_rd <= '1';
elsif dmi_addr = DBG_CORE_LOG_TRIGGER then
log_dmi_trigger <= dmi_din;
end if;
else
report("DMI read from " & to_string(dmi_addr));
end if;
elsif dmi_read_log_data = '0' and dmi_read_log_data_1 = '1' then
-- Increment log_dmi_addr after the end of a read from DBG_CORE_LOG_DATA
log_dmi_addr(LOG_INDEX_BITS + 1 downto 0) <=
std_ulogic_vector(unsigned(log_dmi_addr(LOG_INDEX_BITS+1 downto 0)) + 1);
do_dmi_log_rd <= '1';
end if;
dmi_read_log_data_1 <= dmi_read_log_data;
if dmi_req = '1' and dmi_addr = DBG_CORE_LOG_DATA then
dmi_read_log_data <= '1';
else
dmi_read_log_data <= '0';
end if;
-- Set core stop on terminate. We'll be stopping some time *after*
-- the offending instruction, at least until we can do back flushes
-- that preserve NIA which we can't just yet.
if terminate = '1' then
stopping <= '1';
terminated <= '1';
end if;
end if;
end if;
end process;
gspr_access: process(clk)
variable valid : std_ulogic;
variable sel : spr_selector;
variable isram : std_ulogic;
variable raddr : ramspr_index;
variable odd : std_ulogic;
begin
if rising_edge(clk) then
dbg_gpr_req <= '0';
dbg_spr_req <= '0';
dbg_ls_spr_req <= '0';
if rst = '0' and dmi_req = '1' and dmi_addr = DBG_CORE_GSPR_DATA then
if gspr_index(5) = '0' then
dbg_gpr_req <= '1';
elsif gspr_index(4 downto 2) = "111" then
dbg_ls_spr_req <= '1';
else
dbg_spr_req <= '1';
end if;
end if;
-- Map 0 - 0x1f to GPRs, 0x20 - 0x3f to SPRs, and 0x40 - 0x5f to FPRs
dbg_gpr_addr <= gspr_index(6) & gspr_index(4 downto 0);
dbg_ls_spr_addr <= gspr_index(1 downto 0);
-- For SPRs, use the same mapping as when the fast SPRs were in the GPR file
valid := '1';
sel := "000";
isram := '1';
raddr := (others => '0');
odd := '0';
case gspr_index(4 downto 0) is
when 5x"00" =>
raddr := RAMSPR_LR;
when 5x"01" =>
odd := '1';
raddr := RAMSPR_CTR;
when 5x"02" | 5x"03" =>
odd := gspr_index(0);
raddr := RAMSPR_SRR0;
when 5x"04" | 5x"05" =>
odd := gspr_index(0);
raddr := RAMSPR_HSRR0;
when 5x"06" | 5x"07" =>
odd := gspr_index(0);
raddr := RAMSPR_SPRG0;
when 5x"08" | 5x"09" =>
odd := gspr_index(0);
raddr := RAMSPR_SPRG2;
when 5x"0a" | 5x"0b" =>
odd := gspr_index(0);
raddr := RAMSPR_HSPRG0;
when 5x"0c" =>
isram := '0';
sel := SPRSEL_XER;
when 5x"0d" =>
raddr := RAMSPR_TAR;
when others =>
valid := '0';
end case;
dbg_spr_addr <= isram & sel & std_ulogic_vector(raddr) & odd;
spr_index_valid <= valid;
end if;
end process;
-- Core control signals generated by the debug module
core_stop <= stopping and not do_step;
core_rst <= do_reset;
icache_rst <= do_icreset;
terminated_out <= terminated;
-- Logging RAM
maybe_log: if LOG_LENGTH > 0 generate
subtype log_ptr_t is unsigned(LOG_INDEX_BITS - 1 downto 0);
type log_array_t is array(0 to LOG_LENGTH - 1) of std_ulogic_vector(255 downto 0);
signal log_array : log_array_t;
signal log_rd_ptr : log_ptr_t;
signal log_wr_ptr : log_ptr_t;
signal log_toggle : std_ulogic;
signal log_wr_enable : std_ulogic;
signal log_rd_ptr_latched : log_ptr_t;
signal log_rd : std_ulogic_vector(255 downto 0);
signal log_dmi_reading : std_ulogic;
signal log_dmi_read_done : std_ulogic;
function select_dword(data : std_ulogic_vector(255 downto 0);
addr : std_ulogic_vector(31 downto 0)) return std_ulogic_vector is
variable firstbit : integer;
begin
assert not is_X(addr);
firstbit := to_integer(unsigned(addr(1 downto 0))) * 64;
return data(firstbit + 63 downto firstbit);
end;
attribute ram_style : string;
attribute ram_style of log_array : signal is "block";
attribute ram_decomp : string;
attribute ram_decomp of log_array : signal is "power";
begin
-- Use MSB of read addresses to stop the logging
log_wr_enable <= not (log_read_addr(31) or log_dmi_addr(31) or log_dmi_trigger(1));
log_ram: process(clk)
begin
if rising_edge(clk) then
if log_wr_enable = '1' then
assert not is_X(log_wr_ptr);
log_array(to_integer(log_wr_ptr)) <= log_data;
end if;
if is_X(log_rd_ptr_latched) then
log_rd <= (others => 'X');
else
log_rd <= log_array(to_integer(log_rd_ptr_latched));
end if;
end if;
end process;
log_buffer: process(clk)
variable b : integer;
variable data : std_ulogic_vector(255 downto 0);
begin
if rising_edge(clk) then
if rst = '1' then
log_wr_ptr <= (others => '0');
log_toggle <= '0';
log_rd_ptr_latched <= (others => '0');
elsif log_wr_enable = '1' then
if log_wr_ptr = to_unsigned(LOG_LENGTH - 1, LOG_INDEX_BITS) then
log_toggle <= not log_toggle;
end if;
log_wr_ptr <= log_wr_ptr + 1;
end if;
if do_dmi_log_rd = '1' then
log_rd_ptr_latched <= unsigned(log_dmi_addr(LOG_INDEX_BITS + 1 downto 2));
else
log_rd_ptr_latched <= unsigned(log_read_addr(LOG_INDEX_BITS + 1 downto 2));
end if;
if log_dmi_read_done = '1' then
log_dmi_data <= select_dword(log_rd, log_dmi_addr);
else
log_read_data <= select_dword(log_rd, log_read_addr);
end if;
log_dmi_read_done <= log_dmi_reading;
log_dmi_reading <= do_dmi_log_rd;
do_log_trigger <= '0';
if log_data(42) = log_dmi_trigger(63) and
log_data(41 downto 0) = log_dmi_trigger(43 downto 2) and
log_dmi_trigger(0) = '1' then
do_log_trigger <= '1';
end if;
end if;
end process;
log_write_addr(LOG_INDEX_BITS - 1 downto 0) <= std_ulogic_vector(log_wr_ptr);
log_write_addr(LOG_INDEX_BITS) <= '1';
log_write_addr(31 downto LOG_INDEX_BITS + 1) <= (others => '0');
end generate;
no_log: if LOG_LENGTH = 0 generate
begin
log_read_data <= (others => '0');
log_write_addr <= x"00000001";
end generate;
end behave;