W1: ds2490.c add support for strong pullup
David Fries [Thu, 16 Oct 2008 05:05:03 +0000 (22:05 -0700)]
Add strong pullup support for ds2490 driver, also drop mdelay(750), which
busy waits, usage in favour of msleep for long delays.  Now with msleep
only being called when the strong pullup is active, one wire bus
operations are only taking minimal system overhead.

The new set_pullup will only enable the strong pullup when requested,
which is expected to be the only write operation that will benefit from a
strong pullup.

Signed-off-by: David Fries <david@fries.net>
Signed-off-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/w1/masters/ds2490.c

index c8365fb..6b188e8 100644 (file)
 #define BRANCH_MAIN                    0xCC
 #define BRANCH_AUX                     0x33
 
-/*
- * Duration of the strong pull-up pulse in milliseconds.
- */
-#define PULLUP_PULSE_DURATION          750
-
 /* Status flags */
 #define ST_SPUA                                0x01  /* Strong Pull-up is active */
 #define ST_PRGA                                0x02  /* 12V programming pulse is being generated */
@@ -131,6 +126,11 @@ struct ds_device
 
        int                     ep[NUM_EP];
 
+       /* Strong PullUp
+        * 0: pullup not active, else duration in milliseconds
+        */
+       int                     spu_sleep;
+
        struct w1_bus_master    master;
 };
 
@@ -192,7 +192,7 @@ static int ds_send_control_cmd(struct ds_device *dev, u16 value, u16 index)
 
        return err;
 }
-#if 0
+
 static int ds_send_control_mode(struct ds_device *dev, u16 value, u16 index)
 {
        int err;
@@ -207,7 +207,7 @@ static int ds_send_control_mode(struct ds_device *dev, u16 value, u16 index)
 
        return err;
 }
-#endif
+
 static int ds_send_control(struct ds_device *dev, u16 value, u16 index)
 {
        int err;
@@ -294,14 +294,6 @@ static int ds_recv_status(struct ds_device *dev, struct ds_status *st)
                if (count < 0)
                        return err;
        }
-#if 0
-       if (st->status & ST_IDLE) {
-               printk(KERN_INFO "Resetting pulse after ST_IDLE.\n");
-               err = ds_start_pulse(dev, PULLUP_PULSE_DURATION);
-               if (err)
-                       return err;
-       }
-#endif
 
        return err;
 }
@@ -472,32 +464,26 @@ static int ds_set_speed(struct ds_device *dev, int speed)
 }
 #endif  /*  0  */
 
-static int ds_start_pulse(struct ds_device *dev, int delay)
+static int ds_set_pullup(struct ds_device *dev, int delay)
 {
        int err;
        u8 del = 1 + (u8)(delay >> 4);
-       struct ds_status st;
-
-#if 0
-       err = ds_stop_pulse(dev, 10);
-       if (err)
-               return err;
-
-       err = ds_send_control_mode(dev, MOD_PULSE_EN, PULSE_SPUE);
-       if (err)
-               return err;
-#endif
-       err = ds_send_control(dev, COMM_SET_DURATION | COMM_IM, del);
-       if (err)
-               return err;
 
-       err = ds_send_control(dev, COMM_PULSE | COMM_IM | COMM_F, 0);
+       dev->spu_sleep = 0;
+       err = ds_send_control_mode(dev, MOD_PULSE_EN, delay ? PULSE_SPUE : 0);
        if (err)
                return err;
 
-       mdelay(delay);
+       if (delay) {
+               err = ds_send_control(dev, COMM_SET_DURATION | COMM_IM, del);
+               if (err)
+                       return err;
 
-       ds_wait_status(dev, &st);
+               /* Just storing delay would not get the trunication and
+                * roundup.
+                */
+               dev->spu_sleep = del<<4;
+       }
 
        return err;
 }
@@ -558,6 +544,9 @@ static int ds_write_byte(struct ds_device *dev, u8 byte)
        if (err)
                return err;
 
+       if (dev->spu_sleep)
+               msleep(dev->spu_sleep);
+
        err = ds_wait_status(dev, &st);
        if (err)
                return err;
@@ -566,8 +555,6 @@ static int ds_write_byte(struct ds_device *dev, u8 byte)
        if (err < 0)
                return err;
 
-       ds_start_pulse(dev, PULLUP_PULSE_DURATION);
-
        return !(byte == rbyte);
 }
 
@@ -603,7 +590,7 @@ static int ds_read_block(struct ds_device *dev, u8 *buf, int len)
        if (err < 0)
                return err;
 
-       err = ds_send_control(dev, COMM_BLOCK_IO | COMM_IM | COMM_SPU, len);
+       err = ds_send_control(dev, COMM_BLOCK_IO | COMM_IM, len);
        if (err)
                return err;
 
@@ -630,14 +617,15 @@ static int ds_write_block(struct ds_device *dev, u8 *buf, int len)
        if (err)
                return err;
 
+       if (dev->spu_sleep)
+               msleep(dev->spu_sleep);
+
        ds_wait_status(dev, &st);
 
        err = ds_recv_data(dev, buf, len);
        if (err < 0)
                return err;
 
-       ds_start_pulse(dev, PULLUP_PULSE_DURATION);
-
        return !(err == len);
 }
 
@@ -803,6 +791,16 @@ static u8 ds9490r_reset(void *data)
        return 0;
 }
 
+static u8 ds9490r_set_pullup(void *data, int delay)
+{
+       struct ds_device *dev = data;
+
+       if (ds_set_pullup(dev, delay))
+               return 1;
+
+       return 0;
+}
+
 static int ds_w1_init(struct ds_device *dev)
 {
        memset(&dev->master, 0, sizeof(struct w1_bus_master));
@@ -816,6 +814,7 @@ static int ds_w1_init(struct ds_device *dev)
        dev->master.read_block  = &ds9490r_read_block;
        dev->master.write_block = &ds9490r_write_block;
        dev->master.reset_bus   = &ds9490r_reset;
+       dev->master.set_pullup  = &ds9490r_set_pullup;
 
        return w1_add_master_device(&dev->master);
 }
@@ -839,6 +838,7 @@ static int ds_probe(struct usb_interface *intf,
                printk(KERN_INFO "Failed to allocate new DS9490R structure.\n");
                return -ENOMEM;
        }
+       dev->spu_sleep = 0;
        dev->udev = usb_get_dev(udev);
        if (!dev->udev) {
                err = -ENOMEM;