Re: psmouse.c - synaptics touchpad driver sync problem

[Dmitry Torokhov <dtor_core@ameritech.net>]

On Sunday 09 May 2004 02:30 pm, Thorsten Hirsch wrote:
> Hi again.
> 
> I just wanted to confirm the problem for kernel 2.6.6-rc3-mm2.
> Changelog says that there were patches concerning synaptics and psmouse,
> but they didn't solve my problem.
>
 
Hi,

Could you please try the patch below - it changes the way we process
interrupts from the keyboard controller. Also, in your dmesg, do you see
messages like "psmouse.c: bad data from KBC - timeout"?

--- linus-2.5/drivers/input/serio/i8042.c	2004-05-06 00:54:57.000000000 -0500
+++ dtor/drivers/input/serio/i8042.c	2004-05-06 00:35:32.000000000 -0500
@@ -74,6 +74,14 @@
 	unsigned char *phys;
 };
 
+#define I8042_QUEUE_LEN		64
+struct {
+	unsigned char str[I8042_QUEUE_LEN];
+	unsigned char data[I8042_QUEUE_LEN];
+	unsigned int read_pos;
+	unsigned int write_pos;
+} i8042_buf;
+
 static struct serio i8042_kbd_port;
 static struct serio i8042_aux_port;
 static unsigned char i8042_initial_ctr;
@@ -82,7 +90,7 @@
 static unsigned char i8042_mux_present;
 static unsigned char i8042_sysdev_initialized;
 static struct pm_dev *i8042_pm_dev;
-struct timer_list i8042_timer;
+static struct timer_list i8042_timer;
 
 /*
  * Shared IRQ's require a device pointer, but this driver doesn't support
@@ -374,77 +382,109 @@
 static char i8042_mux_phys[4][32];
 
 /*
- * i8042_interrupt() is the most important function in this driver -
- * it handles the interrupts from the i8042, and sends incoming bytes
- * to the upper layers.
+ * i8042_handle_data() is the most important function in this driver -
+ * it processes data received by i8042_interrupt and sends it to the
+ * upper layers.
  */
 
-static irqreturn_t i8042_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+static void i8042_handle_data(unsigned long notused)
 {
-	unsigned long flags;
 	unsigned char str, data = 0;
 	unsigned int dfl;
-	int ret;
 
-	mod_timer(&i8042_timer, jiffies + I8042_POLL_PERIOD);
+	/*
+	 * No locking it required on i8042_buf as the tasklet is guaranteed
+	 * to be serialized and if write_pos changes while comparing it with
+	 * read_pos another run will be scheduled by i8042_interrupt.
+	 */
+	while (i8042_buf.read_pos != i8042_buf.write_pos) {
 
-	spin_lock_irqsave(&i8042_lock, flags);
-	str = i8042_read_status();
-	if (str & I8042_STR_OBF)
-		data = i8042_read_data();
-	spin_unlock_irqrestore(&i8042_lock, flags);
+		str = i8042_buf.str[i8042_buf.read_pos];
+		data = i8042_buf.data[i8042_buf.read_pos];
 
-	if (~str & I8042_STR_OBF) {
-		if (irq) dbg("Interrupt %d, without any data", irq);
-		ret = 0;
-		goto out;
+		i8042_buf.read_pos++;
+		i8042_buf.read_pos %= I8042_QUEUE_LEN;
+
+		dfl = ((str & I8042_STR_PARITY)  ? SERIO_PARITY  : 0) |
+	      	      ((str & I8042_STR_TIMEOUT) ? SERIO_TIMEOUT : 0);
+
+		if (i8042_mux_values[0].exists && (str & I8042_STR_AUXDATA)) {
+
+			if (str & I8042_STR_MUXERR) {
+				switch (data) {
+					case 0xfd:
+					case 0xfe: dfl = SERIO_TIMEOUT; break;
+					case 0xff: dfl = SERIO_PARITY; break;
+				}
+				data = 0xfe;
+			} else dfl = 0;
+
+			dbg("%02x <- i8042 (interrupt, aux%d, %d%s%s)",
+				data, (str >> 6), irq,
+				dfl & SERIO_PARITY ? ", bad parity" : "",
+				dfl & SERIO_TIMEOUT ? ", timeout" : "");
+
+			serio_interrupt(i8042_mux_port + ((str >> 6) & 3), data, dfl, NULL);
+		} else {
+
+			dbg("%02x <- i8042 (interrupt, %s, %d%s%s)",
+				data, (str & I8042_STR_AUXDATA) ? "aux" : "kbd", irq,
+				dfl & SERIO_PARITY ? ", bad parity" : "",
+				dfl & SERIO_TIMEOUT ? ", timeout" : "");
+
+			if (i8042_aux_values.exists && (str & I8042_STR_AUXDATA))
+				serio_interrupt(&i8042_aux_port, data, dfl, NULL);
+			else if (i8042_kbd_values.exists)
+				serio_interrupt(&i8042_kbd_port, data, dfl, NULL);
+		}
 	}
+}
 
-	dfl = ((str & I8042_STR_PARITY) ? SERIO_PARITY : 0) |
-	      ((str & I8042_STR_TIMEOUT) ? SERIO_TIMEOUT : 0);
+DECLARE_TASKLET(i8042_tasklet, i8042_handle_data, 0);
 
-	if (i8042_mux_values[0].exists && (str & I8042_STR_AUXDATA)) {
+/*
+ * i8042_interrupt() handles the interrupts from i8042 and schedules
+ * i8042_handle_data to process and pass received bytes to the upper
+ * layers.
+ */
 
-		if (str & I8042_STR_MUXERR) {
-			switch (data) {
-				case 0xfd:
-				case 0xfe: dfl = SERIO_TIMEOUT; break;
-				case 0xff: dfl = SERIO_PARITY; break;
-			}
-			data = 0xfe;
-		} else dfl = 0;
+static irqreturn_t i8042_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+{
+	unsigned long flags;
+	unsigned char str;
+	unsigned int n_bytes = 0;
 
-		dbg("%02x <- i8042 (interrupt, aux%d, %d%s%s)",
-			data, (str >> 6), irq, 
-			dfl & SERIO_PARITY ? ", bad parity" : "",
-			dfl & SERIO_TIMEOUT ? ", timeout" : "");
+	mod_timer(&i8042_timer, jiffies + I8042_POLL_PERIOD);
 
-		serio_interrupt(i8042_mux_port + ((str >> 6) & 3), data, dfl, regs);
-		
-		goto irq_ret;
-	}
+	spin_lock_irqsave(&i8042_lock, flags);
+
+	while ((str = i8042_read_status()) & I8042_STR_OBF) {
 
-	dbg("%02x <- i8042 (interrupt, %s, %d%s%s)",
-		data, (str & I8042_STR_AUXDATA) ? "aux" : "kbd", irq, 
-		dfl & SERIO_PARITY ? ", bad parity" : "",
-		dfl & SERIO_TIMEOUT ? ", timeout" : "");
+		n_bytes++;
 
-	if (i8042_aux_values.exists && (str & I8042_STR_AUXDATA)) {
-		serio_interrupt(&i8042_aux_port, data, dfl, regs);
-		goto irq_ret;
+		i8042_buf.str[i8042_buf.write_pos] = str;
+		i8042_buf.data[i8042_buf.write_pos] = i8042_read_data();
+
+		i8042_buf.write_pos++;
+		i8042_buf.write_pos %= I8042_QUEUE_LEN;
+
+		if (unlikely(i8042_buf.write_pos == i8042_buf.read_pos))
+			printk(KERN_WARNING "i8042.c: ring buffer full\n");
 	}
 
-	if (!i8042_kbd_values.exists)
-		goto irq_ret;
+	spin_unlock_irqrestore(&i8042_lock, flags);
+
+	if (unlikely(n_bytes == 0)) {
+		if (irq) dbg("Interrupt %d, without any data", irq);
+		return IRQ_NONE;
+	}
 
-	serio_interrupt(&i8042_kbd_port, data, dfl, regs);
+	tasklet_schedule(&i8042_tasklet);
 
-irq_ret:
-	ret = 1;
-out:
-	return IRQ_RETVAL(ret);
+	return IRQ_HANDLED;
 }
 
+
 /*
  * i8042_enable_mux_mode checks whether the controller has an active
  * multiplexor and puts the chip into Multiplexed (as opposed to
@@ -1011,6 +1051,8 @@
 		if (i8042_mux_values[i].exists)
 			serio_unregister_port(i8042_mux_port + i);
 
+	tasklet_kill(&i8042_tasklet);
+
 	i8042_platform_exit();
 }