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[PARISC] Use work queue in LED/LCD driver instead of tasklet.
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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>
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Grant Grundler authored and Kyle McMartin committed Oct 22, 2005
1 parent ba1f188 commit 3499495
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Showing 3 changed files with 112 additions and 124 deletions.
8 changes: 0 additions & 8 deletions arch/parisc/kernel/time.c
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Original file line number Diff line number Diff line change
Expand Up @@ -89,14 +89,6 @@ irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
}
}

#ifdef CONFIG_CHASSIS_LCD_LED
/* Only schedule the led tasklet on cpu 0, and only if it
* is enabled.
*/
if (cpu == 0 && !atomic_read(&led_tasklet.count))
tasklet_schedule(&led_tasklet);
#endif

/* check soft power switch status */
if (cpu == 0 && !atomic_read(&power_tasklet.count))
tasklet_schedule(&power_tasklet);
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225 changes: 112 additions & 113 deletions drivers/parisc/led.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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>
Expand All @@ -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>
Expand All @@ -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 */
Expand Down Expand Up @@ -116,12 +125,27 @@ lcd_info __attribute__((aligned(8))) =
#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)
Expand Down Expand Up @@ -286,52 +310,35 @@ static void led_LASI_driver(unsigned char leds)
/*
**
** 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);
}
}
}

Expand All @@ -356,7 +363,7 @@ static __inline__ int led_get_net_activity(void)

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();
Expand Down Expand Up @@ -405,94 +412,78 @@ static __inline__ int led_get_diskio_activity(void)
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,
since we only want to know if there was activity or not. */
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)
{
/* 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;
}

/* look for network activity and flash LEDs respectively */
if (led_lanrxtx && ((NORMALIZED_COUNT(count)+(8/2)) & 7) == 0)
if (likely(led_heartbeat))
{
currentleds &= ~(LED_LAN_RCV | LED_LAN_TX);
currentleds |= led_get_net_activity();
/* 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;
}

/* 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;
}

/* update the LCD/LEDs */
if (currentleds != lastleds) {
led_func_ptr(currentleds);
lastleds = currentleds;
}
}

/* main led tasklet struct (scheduled from time.c) */
DECLARE_TASKLET_DISABLED(led_tasklet, led_tasklet_func, 0);
if (currentleds != lastleds)
{
led_func_ptr(currentleds); /* Update the LCD/LEDs */
lastleds = currentleds;
}

queue_delayed_work(led_wq, &led_task, LED_UPDATE_INTERVAL);
}

/*
** led_halt()
Expand Down Expand Up @@ -522,9 +513,13 @@ static int led_halt(struct notifier_block *nb, unsigned long event, void *buf)
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
Expand Down Expand Up @@ -559,7 +554,6 @@ int __init register_led_driver(int model, unsigned long cmd_reg, unsigned long d
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;

Expand Down Expand Up @@ -589,9 +583,11 @@ int __init register_led_driver(int model, unsigned long cmd_reg, unsigned long d
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;
}

Expand Down Expand Up @@ -626,8 +622,8 @@ void __init register_led_regions(void)
** 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 )
Expand All @@ -637,12 +633,13 @@ int lcd_print( char *str )
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);
Expand All @@ -656,8 +653,10 @@ int lcd_print( char *str )
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;
}
Expand Down
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