[PARISC] Use work queue in LED/LCD driver instead of tasklet.
2.6.12-rc1-pa6 use work queue in LED/LCD driver instead of tasklet.
Main advantage is it allows use of msleep() in the led_LCD_driver to
"atomically" perform two MMIO writes (CMD, then DATA).
Lead to nice cleanup of the main led_work_func() and led_LCD_driver().
Kudos to David for being persistent.
From: David Pye <dmp@davidmpye.dyndns.org>
Signed-off-by: Grant Grundler <grundler@parisc-linux.org>
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>
diff --git a/drivers/parisc/led.c b/drivers/parisc/led.c
index 2869022..95bd07b 100644
--- a/drivers/parisc/led.c
+++ b/drivers/parisc/led.c
@@ -18,6 +18,9 @@
* Changes:
* - Audit copy_from_user in led_proc_write.
* Daniele Bellucci <bellucda@tiscali.it>
+ * - Switch from using a tasklet to a work queue, so the led_LCD_driver
+ * can sleep.
+ * David Pye <dmp@davidmpye.dyndns.org>
*/
#include <linux/config.h>
@@ -37,6 +40,7 @@
#include <linux/proc_fs.h>
#include <linux/ctype.h>
#include <linux/blkdev.h>
+#include <linux/workqueue.h>
#include <linux/rcupdate.h>
#include <asm/io.h>
#include <asm/processor.h>
@@ -47,25 +51,30 @@
#include <asm/uaccess.h>
/* The control of the LEDs and LCDs on PARISC-machines have to be done
- completely in software. The necessary calculations are done in a tasklet
- which is scheduled at every timer interrupt and since the calculations
- may consume relatively much CPU-time some of the calculations can be
+ completely in software. The necessary calculations are done in a work queue
+ task which is scheduled regularly, and since the calculations may consume a
+ relatively large amount of CPU time, some of the calculations can be
turned off with the following variables (controlled via procfs) */
static int led_type = -1;
-static int led_heartbeat = 1;
-static int led_diskio = 1;
-static int led_lanrxtx = 1;
+static unsigned char lastleds; /* LED state from most recent update */
+static unsigned int led_heartbeat = 1;
+static unsigned int led_diskio = 1;
+static unsigned int led_lanrxtx = 1;
static char lcd_text[32];
static char lcd_text_default[32];
+
+static struct workqueue_struct *led_wq;
+static void led_work_func(void *);
+static DECLARE_WORK(led_task, led_work_func, NULL);
+
#if 0
#define DPRINTK(x) printk x
#else
#define DPRINTK(x)
#endif
-
struct lcd_block {
unsigned char command; /* stores the command byte */
unsigned char on; /* value for turning LED on */
@@ -116,12 +125,27 @@
#define LCD_DATA_REG lcd_info.lcd_data_reg_addr
#define LED_DATA_REG lcd_info.lcd_cmd_reg_addr /* LASI & ASP only */
+#define LED_HASLCD 1
+#define LED_NOLCD 0
+
+/* The workqueue must be created at init-time */
+static int start_task(void)
+{
+ /* Display the default text now */
+ if (led_type == LED_HASLCD) lcd_print( lcd_text_default );
+
+ /* Create the work queue and queue the LED task */
+ led_wq = create_singlethread_workqueue("led_wq");
+ queue_work(led_wq, &led_task);
+
+ return 0;
+}
+
+device_initcall(start_task);
/* ptr to LCD/LED-specific function */
static void (*led_func_ptr) (unsigned char);
-#define LED_HASLCD 1
-#define LED_NOLCD 0
#ifdef CONFIG_PROC_FS
static int led_proc_read(char *page, char **start, off_t off, int count,
int *eof, void *data)
@@ -286,52 +310,35 @@
/*
**
** led_LCD_driver()
- **
- ** The logic of the LCD driver is, that we write at every scheduled call
- ** only to one of LCD_CMD_REG _or_ LCD_DATA_REG - registers.
- ** That way we don't need to let this tasklet busywait for min_cmd_delay
- ** milliseconds.
- **
- ** TODO: check the value of "min_cmd_delay" against the value of HZ.
**
*/
static void led_LCD_driver(unsigned char leds)
{
- static int last_index; /* 0:heartbeat, 1:disk, 2:lan_in, 3:lan_out */
- static int last_was_cmd;/* 0: CMD was written last, 1: DATA was last */
- struct lcd_block *block_ptr;
- int value;
-
- switch (last_index) {
- case 0: block_ptr = &lcd_info.heartbeat;
- value = leds & LED_HEARTBEAT;
- break;
- case 1: block_ptr = &lcd_info.disk_io;
- value = leds & LED_DISK_IO;
- break;
- case 2: block_ptr = &lcd_info.lan_rcv;
- value = leds & LED_LAN_RCV;
- break;
- case 3: block_ptr = &lcd_info.lan_tx;
- value = leds & LED_LAN_TX;
- break;
- default: /* should never happen: */
- return;
- }
-
- if (last_was_cmd) {
- /* write the value to the LCD data port */
- gsc_writeb( value ? block_ptr->on : block_ptr->off, LCD_DATA_REG );
- } else {
- /* write the command-byte to the LCD command register */
- gsc_writeb( block_ptr->command, LCD_CMD_REG );
- }
+ static int i;
+ static unsigned char mask[4] = { LED_HEARTBEAT, LED_DISK_IO,
+ LED_LAN_RCV, LED_LAN_TX };
- /* now update the vars for the next interrupt iteration */
- if (++last_was_cmd == 2) { /* switch between cmd & data */
- last_was_cmd = 0;
- if (++last_index == 4)
- last_index = 0; /* switch back to heartbeat index */
+ static struct lcd_block * blockp[4] = {
+ &lcd_info.heartbeat,
+ &lcd_info.disk_io,
+ &lcd_info.lan_rcv,
+ &lcd_info.lan_tx
+ };
+
+ /* Convert min_cmd_delay to milliseconds */
+ unsigned int msec_cmd_delay = 1 + (lcd_info.min_cmd_delay / 1000);
+
+ for (i=0; i<4; ++i)
+ {
+ if ((leds & mask[i]) != (lastleds & mask[i]))
+ {
+ gsc_writeb( blockp[i]->command, LCD_CMD_REG );
+ msleep(msec_cmd_delay);
+
+ gsc_writeb( leds & mask[i] ? blockp[i]->on :
+ blockp[i]->off, LCD_DATA_REG );
+ msleep(msec_cmd_delay);
+ }
}
}
@@ -356,7 +363,7 @@
rx_total = tx_total = 0;
- /* we are running as tasklet, so locking dev_base
+ /* we are running as a workqueue task, so locking dev_base
* for reading should be OK */
read_lock(&dev_base_lock);
rcu_read_lock();
@@ -405,7 +412,7 @@
static unsigned long last_pgpgin, last_pgpgout;
struct page_state pgstat;
int changed;
-
+
get_full_page_state(&pgstat); /* get no of sectors in & out */
/* Just use a very simple calculation here. Do not care about overflow,
@@ -413,87 +420,71 @@
changed = (pgstat.pgpgin != last_pgpgin) || (pgstat.pgpgout != last_pgpgout);
last_pgpgin = pgstat.pgpgin;
last_pgpgout = pgstat.pgpgout;
-
+
return (changed ? LED_DISK_IO : 0);
}
/*
- ** led_tasklet_func()
+ ** led_work_func()
**
- ** is scheduled at every timer interrupt from time.c and
- ** updates the chassis LCD/LED
+ ** manages when and which chassis LCD/LED gets updated
TODO:
- display load average (older machines like 715/64 have 4 "free" LED's for that)
- optimizations
*/
-#define HEARTBEAT_LEN (HZ*6/100)
-#define HEARTBEAT_2ND_RANGE_START (HZ*22/100)
+#define HEARTBEAT_LEN (HZ*10/100)
+#define HEARTBEAT_2ND_RANGE_START (HZ*28/100)
#define HEARTBEAT_2ND_RANGE_END (HEARTBEAT_2ND_RANGE_START + HEARTBEAT_LEN)
-#define NORMALIZED_COUNT(count) (count/(HZ/100))
+#define LED_UPDATE_INTERVAL (1 + (HZ*19/1000))
-static void led_tasklet_func(unsigned long unused)
+static void led_work_func (void *unused)
{
- static unsigned char lastleds;
- unsigned char currentleds; /* stores current value of the LEDs */
- static unsigned long count; /* static incremented value, not wrapped */
+ static unsigned long last_jiffies;
static unsigned long count_HZ; /* counter in range 0..HZ */
+ unsigned char currentleds = 0; /* stores current value of the LEDs */
/* exit if not initialized */
if (!led_func_ptr)
return;
- /* increment the local counters */
- ++count;
- if (++count_HZ == HZ)
+ /* increment the heartbeat timekeeper */
+ count_HZ += jiffies - last_jiffies;
+ last_jiffies = jiffies;
+ if (count_HZ >= HZ)
count_HZ = 0;
- currentleds = lastleds;
-
- if (led_heartbeat)
+ if (likely(led_heartbeat))
{
- /* flash heartbeat-LED like a real heart (2 x short then a long delay) */
- if (count_HZ<HEARTBEAT_LEN ||
- (count_HZ>=HEARTBEAT_2ND_RANGE_START && count_HZ<HEARTBEAT_2ND_RANGE_END))
- currentleds |= LED_HEARTBEAT;
- else
- currentleds &= ~LED_HEARTBEAT;
+ /* flash heartbeat-LED like a real heart
+ * (2 x short then a long delay)
+ */
+ if (count_HZ < HEARTBEAT_LEN ||
+ (count_HZ >= HEARTBEAT_2ND_RANGE_START &&
+ count_HZ < HEARTBEAT_2ND_RANGE_END))
+ currentleds |= LED_HEARTBEAT;
}
- /* look for network activity and flash LEDs respectively */
- if (led_lanrxtx && ((NORMALIZED_COUNT(count)+(8/2)) & 7) == 0)
- {
- currentleds &= ~(LED_LAN_RCV | LED_LAN_TX);
- currentleds |= led_get_net_activity();
- }
-
- /* avoid to calculate diskio-stats at same irq as netio-stats */
- if (led_diskio && (NORMALIZED_COUNT(count) & 7) == 0)
- {
- currentleds &= ~LED_DISK_IO;
- currentleds |= led_get_diskio_activity();
- }
+ if (likely(led_lanrxtx)) currentleds |= led_get_net_activity();
+ if (likely(led_diskio)) currentleds |= led_get_diskio_activity();
/* blink all LEDs twice a second if we got an Oops (HPMC) */
- if (oops_in_progress) {
+ if (unlikely(oops_in_progress))
currentleds = (count_HZ<=(HZ/2)) ? 0 : 0xff;
+
+ if (currentleds != lastleds)
+ {
+ led_func_ptr(currentleds); /* Update the LCD/LEDs */
+ lastleds = currentleds;
}
-
- /* update the LCD/LEDs */
- if (currentleds != lastleds) {
- led_func_ptr(currentleds);
- lastleds = currentleds;
- }
+
+ queue_delayed_work(led_wq, &led_task, LED_UPDATE_INTERVAL);
}
-/* main led tasklet struct (scheduled from time.c) */
-DECLARE_TASKLET_DISABLED(led_tasklet, led_tasklet_func, 0);
-
-
/*
** led_halt()
**
@@ -522,9 +513,13 @@
default: return NOTIFY_DONE;
}
- /* completely stop the LED/LCD tasklet */
- tasklet_disable(&led_tasklet);
-
+ /* Cancel the work item and delete the queue */
+ if (led_wq) {
+ cancel_rearming_delayed_workqueue(led_wq, &led_task);
+ destroy_workqueue(led_wq);
+ led_wq = NULL;
+ }
+
if (lcd_info.model == DISPLAY_MODEL_LCD)
lcd_print(txt);
else
@@ -559,7 +554,6 @@
printk(KERN_INFO "LCD display at %lx,%lx registered\n",
LCD_CMD_REG , LCD_DATA_REG);
led_func_ptr = led_LCD_driver;
- lcd_print( lcd_text_default );
led_type = LED_HASLCD;
break;
@@ -589,9 +583,11 @@
initialized++;
register_reboot_notifier(&led_notifier);
- /* start the led tasklet for the first time */
- tasklet_enable(&led_tasklet);
-
+ /* Ensure the work is queued */
+ if (led_wq) {
+ queue_work(led_wq, &led_task);
+ }
+
return 0;
}
@@ -626,8 +622,8 @@
** lcd_print()
**
** Displays the given string on the LCD-Display of newer machines.
- ** lcd_print() disables the timer-based led tasklet during its
- ** execution and enables it afterwards again.
+ ** lcd_print() disables/enables the timer-based led work queue to
+ ** avoid a race condition while writing the CMD/DATA register pair.
**
*/
int lcd_print( char *str )
@@ -637,12 +633,13 @@
if (!led_func_ptr || lcd_info.model != DISPLAY_MODEL_LCD)
return 0;
- /* temporarily disable the led tasklet */
- tasklet_disable(&led_tasklet);
+ /* temporarily disable the led work task */
+ if (led_wq)
+ cancel_rearming_delayed_workqueue(led_wq, &led_task);
/* copy display string to buffer for procfs */
strlcpy(lcd_text, str, sizeof(lcd_text));
-
+
/* Set LCD Cursor to 1st character */
gsc_writeb(lcd_info.reset_cmd1, LCD_CMD_REG);
udelay(lcd_info.min_cmd_delay);
@@ -656,8 +653,10 @@
udelay(lcd_info.min_cmd_delay);
}
- /* re-enable the led tasklet */
- tasklet_enable(&led_tasklet);
+ /* re-queue the work */
+ if (led_wq) {
+ queue_work(led_wq, &led_task);
+ }
return lcd_info.lcd_width;
}