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Improve PLL/MMCM clocks configuration

Browse Source 
We can now pass both the input clock and target clock frequency
via generics. Add support for both 50Mhz and 100Mhz target freqs
for both cases.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
pull/77/head
Benjamin Herrenschmidt 5 years ago
parent 5f28109957
commit 9961d70dfb
4 changed files with 176 additions and 76 deletions
Show Stats Download Patch File Download Diff File

74
fpga/clk_gen_mcmm.vhd
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@ -6,7 +6,9 @@ use UNISIM.vcomponents.all;

entity clock_generator is
generic (
clk_period_hz : positive := 12000000);
CLK_INPUT_HZ : positive := 12000000;
CLK_OUTPUT_HZ : positive := 50000000
);
port (
ext_clk : in std_logic;
pll_rst_in : in std_logic;
@ -22,28 +24,66 @@ architecture rtl of clock_generator is
clkfbout_mult : real range 2.0 to 64.0;
clkout_divide : real range 1.0 to 128.0;
divclk_divide : integer range 1 to 106;
force_rst : std_ulogic;
end record;

function gen_pll_settings (
constant freq_hz : positive)
constant input_hz : positive;
constant output_hz : positive)
return pll_settings_t is

constant bad_settings : pll_settings_t :=
(clkin_period => 0.0,
clkfbout_mult => 2.0,
clkout_divide => 1.0,
divclk_divide => 1,
force_rst => '1');
begin
if freq_hz = 100000000 then
return (clkin_period => 10.0,
clkfbout_mult => 16.0,
clkout_divide => 32.0,
divclk_divide => 1);
elsif freq_hz = 12000000 then
return (clkin_period => 83.33,
clkfbout_mult => 50.0,
clkout_divide => 12.0,
divclk_divide => 1);
else
report "Unsupported input frequency" severity failure;
end if;
case input_hz is
when 100000000 =>
case output_hz is
when 100000000 =>
return (clkin_period => 10.0,
clkfbout_mult => 16.0,
clkout_divide => 16.0,
divclk_divide => 1,
force_rst => '0');
when 50000000 =>
return (clkin_period => 10.0,
clkfbout_mult => 16.0,
clkout_divide => 32.0,
divclk_divide => 1,
force_rst => '0');
when others =>
report "Unsupported output frequency" severity failure;
return bad_settings;
end case;
when 12000000 =>
case output_hz is
when 100000000 =>
return (clkin_period => 83.33,
clkfbout_mult => 50.0,
clkout_divide => 6.0,
divclk_divide => 1,
force_rst => '0');
when 50000000 =>
return (clkin_period => 83.33,
clkfbout_mult => 50.0,
clkout_divide => 12.0,
divclk_divide => 1,
force_rst => '0');
when others =>
report "Unsupported output frequency" severity failure;
return bad_settings;
end case;
when others =>
report "Unsupported input frequency" severity failure;
return bad_settings;
end case;
end function gen_pll_settings;

constant pll_settings : pll_settings_t := gen_pll_settings(clk_period_hz);
constant pll_settings : pll_settings_t := gen_pll_settings(clk_input_hz,
clk_output_hz);
begin
pll : MMCME2_BASE
generic map (
@ -71,6 +111,6 @@ begin
CLKFBIN => clkfb,
CLKIN1 => ext_clk,
PWRDWN => '0',
RST => pll_rst_in
RST => pll_rst_in or pll_settings.force_rst
);
end architecture rtl;

128
fpga/clk_gen_plle2.vhd
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@ -5,67 +5,89 @@ Library UNISIM;
use UNISIM.vcomponents.all;

entity clock_generator is
generic (
clk_period_hz : positive := 100000000);
port (
ext_clk : in std_logic;
pll_rst_in : in std_logic;
pll_clk_out : out std_logic;
pll_locked_out : out std_logic);
generic (
CLK_INPUT_HZ : positive := 100000000;
CLK_OUTPUT_HZ : positive := 100000000
);
port (
ext_clk : in std_logic;
pll_rst_in : in std_logic;
pll_clk_out : out std_logic;
pll_locked_out : out std_logic);
end entity clock_generator;

architecture rtl of clock_generator is
signal clkfb : std_ulogic;

signal clkfb : std_ulogic;
type pll_settings_t is record
clkin_period : real range 0.000 to 52.631;
clkfbout_mult : integer range 2 to 64;
clkout_divide : integer range 1 to 128;
divclk_divide : integer range 1 to 56;
force_rst : std_ulogic;
end record;

type pll_settings_t is record
clkin_period : real range 0.000 to 52.631;
clkfbout_mult : integer range 2 to 64;
clkout_divide : integer range 1 to 128;
divclk_divide : integer range 1 to 56;
end record;
function gen_pll_settings (
constant input_hz : positive;
constant output_hz : positive)
return pll_settings_t is

function gen_pll_settings (
constant freq_hz : positive)
return pll_settings_t is
begin
if freq_hz = 100000000 then
return (clkin_period => 10.0,
clkfbout_mult => 16,
clkout_divide => 32,
divclk_divide => 1);
else
report "Unsupported input frequency" severity failure;
-- return (clkin_period => 0.0,
-- clkfbout_mult => 0,
-- clkout_divide => 0,
-- divclk_divide => 0);
end if;
end function gen_pll_settings;
constant bad_settings : pll_settings_t :=
(clkin_period => 0.0,
clkfbout_mult => 2,
clkout_divide => 1,
divclk_divide => 1,
force_rst => '1');
begin
case input_hz is
when 100000000 =>
case output_hz is
when 100000000 =>
return (clkin_period => 10.0,
clkfbout_mult => 16,
clkout_divide => 16,
divclk_divide => 1,
force_rst => '0');
when 50000000 =>
return (clkin_period => 10.0,
clkfbout_mult => 16,
clkout_divide => 32,
divclk_divide => 1,
force_rst => '0');
when others =>
report "Unsupported output frequency" severity failure;
return bad_settings;
end case;
when others =>
report "Unsupported input frequency" severity failure;
return bad_settings;
end case;
end function gen_pll_settings;

constant pll_settings : pll_settings_t := gen_pll_settings(clk_period_hz);
constant pll_settings : pll_settings_t := gen_pll_settings(clk_input_hz,
clk_output_hz);
begin

pll : PLLE2_BASE
generic map (
BANDWIDTH => "OPTIMIZED",
CLKFBOUT_MULT => pll_settings.clkfbout_mult,
CLKIN1_PERIOD => pll_settings.clkin_period,
CLKOUT0_DIVIDE => pll_settings.clkout_divide,
DIVCLK_DIVIDE => pll_settings.divclk_divide,
STARTUP_WAIT => "FALSE")
port map (
CLKOUT0 => pll_clk_out,
CLKOUT1 => open,
CLKOUT2 => open,
CLKOUT3 => open,
CLKOUT4 => open,
CLKOUT5 => open,
CLKFBOUT => clkfb,
LOCKED => pll_locked_out,
CLKIN1 => ext_clk,
PWRDWN => '0',
RST => pll_rst_in,
CLKFBIN => clkfb);
pll : PLLE2_BASE
generic map (
BANDWIDTH => "OPTIMIZED",
CLKFBOUT_MULT => pll_settings.clkfbout_mult,
CLKIN1_PERIOD => pll_settings.clkin_period,
CLKOUT0_DIVIDE => pll_settings.clkout_divide,
DIVCLK_DIVIDE => pll_settings.divclk_divide,
STARTUP_WAIT => "FALSE")
port map (
CLKOUT0 => pll_clk_out,
CLKOUT1 => open,
CLKOUT2 => open,
CLKOUT3 => open,
CLKOUT4 => open,
CLKOUT5 => open,
CLKFBOUT => clkfb,
LOCKED => pll_locked_out,
CLKIN1 => ext_clk,
PWRDWN => '0',
RST => pll_rst_in or pll_settings.force_rst,
CLKFBIN => clkfb);

end architecture rtl;

8
fpga/toplevel.vhdl
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@ -5,7 +5,9 @@ entity toplevel is
generic (
MEMORY_SIZE : positive := 524288;
RAM_INIT_FILE : string := "firmware.hex";
RESET_LOW : boolean := true
RESET_LOW : boolean := true;
CLK_INPUT : positive := 100000000;
CLK_FREQUENCY : positive := 100000000
);
port(
ext_clk : in std_ulogic;
@ -43,6 +45,10 @@ begin
);

clkgen: entity work.clock_generator
generic map(
CLK_INPUT_HZ => CLK_INPUT,
CLK_OUTPUT_HZ => CLK_FREQUENCY
)
port map(
ext_clk => ext_clk,
pll_rst_in => pll_rst,

42
microwatt.core
Unescape Escape View File

@ -81,7 +81,11 @@ targets:
nexys_a7:
default_tool: vivado
filesets: [core, nexys_a7, soc, fpga, debug_xilinx]
parameters : [memory_size, ram_init_file]
parameters :
- memory_size
- ram_init_file
- clk_input
- clk_frequency
tools:
vivado: {part : xc7a100tcsg324-1}
toplevel : toplevel
@ -89,7 +93,11 @@ targets:
nexys_video:
default_tool: vivado
filesets: [core, nexys_video, soc, fpga, debug_xilinx]
parameters : [memory_size, ram_init_file]
parameters :
- memory_size
- ram_init_file
- clk_input
- clk_frequency
tools:
vivado: {part : xc7a200tsbg484-1}
toplevel : toplevel
@ -97,7 +105,11 @@ targets:
arty_a7-35:
default_tool: vivado
filesets: [core, arty_a7, soc, fpga, debug_xilinx]
parameters : [memory_size, ram_init_file]
parameters :
- memory_size
- ram_init_file
- clk_input
- clk_frequency
tools:
vivado: {part : xc7a35ticsg324-1L}
toplevel : toplevel
@ -105,7 +117,11 @@ targets:
arty_a7-100:
default_tool: vivado
filesets: [core, arty_a7, soc, fpga, debug_xilinx]
parameters : [memory_size, ram_init_file]
parameters :
- memory_size
- ram_init_file
- clk_input
- clk_frequency
tools:
vivado: {part : xc7a100ticsg324-1L}
toplevel : toplevel
@ -113,7 +129,11 @@ targets:
cmod_a7-35:
default_tool: vivado
filesets: [core, cmod_a7-35, soc, fpga, debug_xilinx]
parameters : [memory_size, ram_init_file, reset_low=false]
parameters :
- memory_size
- ram_init_file
- reset_low=false
- clk_input=12000000
tools:
vivado: {part : xc7a35tcpg236-1}
toplevel : toplevel
@ -139,3 +159,15 @@ parameters:
datatype : bool
description : External reset button polarity
paramtype : generic

clk_input:
datatype : int
description : Clock input frequency in HZ (for top-generic based boards)
paramtype : generic
default : 100000000

clk_frequency:
datatype : int
description : Generated system clock frequency in HZ (for top-generic based boards)
paramtype : generic
default : 50000000

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