timer: atomic reads

milkymist/timer/__init__.py

@@ -5,9 +5,11 @@ from migen.bank.eventmanager import *
 
 class Timer(Module, AutoCSR):
 	def __init__(self, width=32):
-		self._en = CSRStorage()
-		self._value = CSRStorage(width, write_from_dev=True)
+		self._load = CSRStorage(width)
 		self._reload = CSRStorage(width)
+		self._en = CSRStorage()
+		self._update_value = CSR()
+		self._value = CSRStatus(width)
 		
 		self.submodules.ev = EventManager()
 		self.ev.zero = EventSourceProcess()
@@ -15,12 +17,18 @@ class Timer(Module, AutoCSR):
 
 		###
 
-		self.comb += [
-			If(self._value.storage == 0,
-				self._value.dat_w.eq(self._reload.storage)
+		value = Signal(width)
+		self.sync += [
+			If(self._en.storage,
+				If(value == 0,
+					# set reload to 0 to disable reloading
+					value.eq(self._reload.storage)
+				).Else(
+					value.eq(value - 1)
+				)
 			).Else(
-				self._value.dat_w.eq(self._value.storage - 1)
+				value.eq(self._load.storage)
 			),
-			self._value.we.eq(self._en.storage),
-			self.ev.zero.trigger.eq(self._value.storage != 0)
+			If(self._update_value.re, self._value.status.eq(value))
 		]
+		self.comb += self.ev.zero.trigger.eq(value != 0)

software/bios/boot.c

@@ -7,9 +7,9 @@
 #include <sfl.h>
 #include <string.h>
 #include <irq.h>
-#include <timer.h>
 
 #include <hw/mem.h>
+#include <hw/csr.h>
 
 #include <net/microudp.h>
 #include <net/tftp.h>
@@ -33,12 +33,13 @@ static int check_ack(void)
 	int recognized;
 	static const char str[SFL_MAGIC_LEN] = SFL_MAGIC_ACK;
 
-	timer_enable(0);
-	timer_set_reload(0);
-	timer_set_counter(get_system_frequency()/4);
-	timer_enable(1);
+	timer0_en_write(0);
+	timer0_reload_write(0);
+	timer0_load_write(identifier_frequency_read()/4);
+	timer0_en_write(1);
+	timer0_update_value_write(1);
 	recognized = 0;
-	while(timer_get()) {
+	while(timer0_value_read()) {
 		if(uart_read_nonblock()) {
 			char c;
 			c = uart_read();
@@ -53,6 +54,7 @@ static int check_ack(void)
 					recognized = 0;
 			}
 		}
+		timer0_update_value_write(1);
 	}
 	return 0;
 }

software/bios/main.c

@@ -8,8 +8,8 @@
 #include <irq.h>
 #include <version.h>
 #include <crc.h>
-#include <timer.h>
 
+#include <hw/csr.h>
 #include <hw/mem.h>
 #include <net/microudp.h>
 
@@ -459,11 +459,12 @@ static int test_user_abort(void)
 	printf("Q/ESC: abort boot\n");
 	printf("F7:    boot from serial\n");
 	printf("F8:    boot from network\n");
-	timer_enable(0);
-	timer_set_reload(0);
-	timer_set_counter(get_system_frequency()*2);
-	timer_enable(1);
-	while(timer_get()) {
+	timer0_en_write(0);
+	timer0_reload_write(0);
+	timer0_load_write(identifier_frequency_read()*2);
+	timer0_en_write(1);
+	timer0_update_value_write(1);
+	while(timer0_value_read()) {
 		if(readchar_nonblock()) {
 			c = readchar();
 			if((c == 'Q')||(c == '\e')) {
@@ -479,6 +480,7 @@ static int test_user_abort(void)
 				return 0;
 			}
 		}
+		timer0_update_value_write(1);
 	}
 	return 1;
 }

software/include/base/timer.h

@@ -1,19 +0,0 @@
-#ifndef __TIMER_H
-#define __TIMER_H
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-unsigned int get_system_frequency(void);
-void timer_enable(int en);
-unsigned int timer_get(void);
-void timer_set_counter(unsigned int value);
-void timer_set_reload(unsigned int value);
-void busy_wait(unsigned int ms);
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif /* __TIMER_H */

software/libbase/Makefile

@@ -1,7 +1,7 @@
 M2DIR=../..
 include $(M2DIR)/software/common.mak
 
-OBJECTS=setjmp.o libc.o errno.o crc16.o crc32.o console.o timer.o system.o board.o uart.o vsnprintf.o strtod.o qsort.o
+OBJECTS=setjmp.o libc.o errno.o crc16.o crc32.o console.o system.o board.o uart.o vsnprintf.o strtod.o qsort.o
 
 all: libbase.a
 

software/libbase/board.c

@@ -3,7 +3,6 @@
 #include <stdlib.h>
 #include <string.h>
 #include <version.h>
-#include <timer.h>
 #include <board.h>
 
 static const struct board_desc boards[1] = {
@@ -88,7 +87,7 @@ void board_init(void)
 	}
 	rev = get_pcb_revision();
 	get_soc_version_formatted(soc_version);
-	printf("Detected SoC %s at %dMHz on %s (PCB revision %d)\n", soc_version, get_system_frequency()/1000000,
+	printf("Detected SoC %s at %dMHz on %s (PCB revision %d)\n", soc_version, identifier_frequency_read()/1000000,
 	       brd_desc->name, rev);
 	if(strcmp(soc_version, VERSION) != 0)
 		printf("SoC and BIOS versions do not match!\n");

software/libbase/timer.c

@@ -1,37 +0,0 @@
-#include <hw/csr.h>
-
-#include "timer.h"
-
-unsigned int get_system_frequency(void)
-{
-	return identifier_frequency_read();
-}
-
-void timer_enable(int en)
-{
-	timer0_en_write(en);
-}
-
-unsigned int timer_get(void)
-{
-	return timer0_value_read();
-}
-
-void timer_set_counter(unsigned int value)
-{
-	timer0_value_write(value);
-}
-
-void timer_set_reload(unsigned int value)
-{
-	timer0_reload_write(value);
-}
-
-void busy_wait(unsigned int ds)
-{
-	timer_enable(0);
-	timer_set_reload(0);
-	timer_set_counter(get_system_frequency()/10*ds);
-	timer_enable(1);
-	while(timer_get());
-}

software/libnet/microudp.c

@@ -1,7 +1,6 @@
 #include <stdio.h>
 #include <system.h>
 #include <crc.h>
-#include <timer.h>
 #include <hw/csr.h>
 #include <hw/flags.h>
 #include <hw/mem.h>
@@ -388,6 +387,16 @@ void microudp_service(void)
 	}
 }
 
+static void busy_wait(unsigned int ds)
+{
+	timer0_en_write(0);
+	timer0_reload_write(0);
+	timer0_load_write(identifier_frequency_read()/10*ds);
+	timer0_en_write(1);
+	timer0_update_value_write(1);
+	while(timer0_value_read()) timer0_update_value_write(1);
+}
+
 void ethreset(void)
 {
 	minimac_phy_reset_write(0);

software/videomixer/time.c

@@ -4,7 +4,12 @@
 
 void time_init(void)
 {
-	timer0_reload_write(2*identifier_frequency_read());
+	int t;
+
+	timer0_en_write(0);
+	t = 2*identifier_frequency_read();
+	timer0_reload_write(t);
+	timer0_load_write(t);
 	timer0_en_write(1);
 }
 
@@ -12,7 +17,8 @@ int elapsed(int *last_event, int period)
 {
 	int t, dt;
 
-	t = timer0_reload_read() - timer0_value_read(); // TODO: atomic read
+	timer0_update_value_write(1);
+	t = timer0_reload_read() - timer0_value_read();
 	dt = t - *last_event;
 	if(dt < 0)
 		dt += timer0_reload_read();