added memory-mapped io version of i8254_load(), made i8253_cascade_ns_to_timer_2div()

return early if everything is already correct instead of going through loop again

diff --git a/comedi/drivers/8253.h b/comedi/drivers/8253.h
index 87e01911457eaa09e8b65768bd0b927525be38f9..66975036230dab152fc9f6e50cf083e4503ac4dc 100644 (file)
--- a/comedi/drivers/8253.h
+++ b/comedi/drivers/8253.h
@@ -121,6 +121,16 @@ static inline void i8253_cascade_ns_to_timer_2div(int i8253_osc_base,
        unsigned int start;
        unsigned int ns_low, ns_high;
 
+       /* exit early if everything is already correct (this can save time
+        * since this function may be called repeatedly during command tests
+        * and execution) */
+       if(*d1 * *d2 * i8253_osc_base == *nanosec &&
+               *d1 > 1 && *d1 < 0x10000 &&
+               *d2 > 1 && *d2 < 0x10000)
+       {
+               return;
+       }
+
        divider = *nanosec / i8253_osc_base;
 
        div1_lub = div2_lub = 0;
@@ -175,7 +185,7 @@ static inline void i8253_cascade_ns_to_timer_2div(int i8253_osc_base,
        }
 
        *nanosec = div1 * div2 * i8253_osc_base;
-       *d1 = div1 & 0xffff;
+       *d1 = div1 & 0xffff;    // masking is done since counter maps zero to 0x10000
        *d2 = div2 & 0xffff;
        return;
 }
@@ -185,6 +195,8 @@ static inline void i8253_cascade_ns_to_timer_2div(int i8253_osc_base,
  * counter_number is the counter you want to load (0,1 or 2)
  * count is the number to load into the counter.
  * You probably want to use mode 2.
+ * Use i8254_mm_load() if you board uses memory-mapped io, it is
+ * the same as i8254_load() except it uses writeb() instead of outb().
  * FMH
  */
 static inline int i8254_load(unsigned int base_address,
@@ -210,5 +222,28 @@ static inline int i8254_load(unsigned int base_address,
        return 0;
 }
 
+static inline int i8254_mm_load(unsigned int base_address,
+       unsigned int counter_number, unsigned int count, unsigned int mode)
+{
+       unsigned char byte;
+       static const int counter_control = 3;
+
+       if(counter_number > 2) return -1;
+       if(count > 0xffff) return -1;
+       if(mode > 5) return -1;
+       if(mode == 2 && count == 1) return -1;
+
+       byte = counter_number << 6;
+       byte |= 0x30;   // load low then high byte
+       byte |= (mode << 1);    // set counter mode
+       writeb(byte, base_address + counter_control);
+       byte = count & 0xff;    // lsb of counter value
+       writeb(byte, base_address + counter_number);
+       byte = (count >> 8) & 0xff;     // msb of counter value
+       writeb(byte, base_address + counter_number);
+
+       return 0;
+}
+
 #endif