5 files changed, 68 insertions, 25 deletions

diff --git a/firmware/target/arm/as3525/kernel-as3525.c b/firmware/target/arm/as3525/kernel-as3525.c
index ebaef71c99..4ae1a03809 100644
--- a/firmware/target/arm/as3525/kernel-as3525.c
+++ b/firmware/target/arm/as3525/kernel-as3525.c
@@ -25,13 +25,6 @@
 #include "timer.h"
 
 #ifdef HAVE_SCROLLWHEEL
-/* let the timer interrupt twice as often for the scrollwheel polling */
-#define KERNEL_TIMER_FREQ (TIMER_FREQ/2)
-#else
-#define KERNEL_TIMER_FREQ TIMER_FREQ
-#endif
-
-#ifdef HAVE_SCROLLWHEEL
 #include "button-target.h"
 /* The scrollwheel is polled every 5 ms (the tick tasks only every 10) */
 static int poll_scrollwheel = 0;
diff --git a/firmware/target/arm/as3525/sansa-fuzev2/button-fuzev2.c b/firmware/target/arm/as3525/sansa-fuzev2/button-fuzev2.c
index d50df9f1c6..db08414ae5 100644
--- a/firmware/target/arm/as3525/sansa-fuzev2/button-fuzev2.c
+++ b/firmware/target/arm/as3525/sansa-fuzev2/button-fuzev2.c
@@ -58,29 +58,26 @@ void get_scrollwheel(void)
 int button_read_device(void)
 {
     int btn = 0;
-    volatile int delay;
     static bool hold_button_old = false;
     static long power_counter = 0;
     unsigned gpiod6;
 
-    /* if we remove this delay, we see screen corruption (the higher the CPU
-     * frequency the higher the corruption) */
-    for(delay = 1000; delay; delay--)
-        nop;
+
+    /* if we don't wait for the fifo to empty, we'll see screen corruption
+     * (the higher the CPU frequency the higher the corruption) */
+    while ((DBOP_STAT & (1<<10)) == 0);
 
     get_scrollwheel();
 
     CCU_IO &= ~(1<<12);
 
     GPIOB_PIN(0) = 1<<0;
-    for(delay = 500; delay; delay--)
-        nop;
+    udelay(1);
 
     gpiod6 = GPIOD_PIN(6);
 
     GPIOB_PIN(0) = 0;
-    for(delay = 240; delay; delay--)
-        nop;
+    udelay(1);
 
     if (GPIOC_PIN(1) & 1<<1)
         btn |= BUTTON_DOWN;
diff --git a/firmware/target/arm/as3525/sd-as3525.c b/firmware/target/arm/as3525/sd-as3525.c
index 5ccb659e00..1cf7e51cf8 100644
--- a/firmware/target/arm/as3525/sd-as3525.c
+++ b/firmware/target/arm/as3525/sd-as3525.c
@@ -141,13 +141,8 @@ static volatile unsigned int transfer_error[NUM_VOLUMES];
 static unsigned char aligned_buffer[UNALIGNED_NUM_SECTORS* SD_BLOCK_SIZE] __attribute__((aligned(32)));   /* align on cache line size */
 static unsigned char *uncached_buffer = UNCACHED_ADDR(&aligned_buffer[0]);
 
-static inline void mci_delay(void)
-{
-    int i = 0xffff;
-    do {
-        asm volatile("nop\n");
-    } while (--i);
-}
+
+static inline void mci_delay(void) { udelay(1000) ; }
 
 
 static inline bool card_detect_target(void)
@@ -159,6 +154,7 @@ static inline bool card_detect_target(void)
 #endif
 }
 
+
 #ifdef HAVE_HOTSWAP
 static int sd1_oneshot_callback(struct timeout *tmo)
 {
diff --git a/firmware/target/arm/as3525/sd-as3525v2.c b/firmware/target/arm/as3525/sd-as3525v2.c
index baf69760ab..2f263f7378 100644
--- a/firmware/target/arm/as3525/sd-as3525v2.c
+++ b/firmware/target/arm/as3525/sd-as3525v2.c
@@ -344,7 +344,7 @@ static volatile bool retry;
 int active_card = 0;
 #endif
 
-static inline void mci_delay(void) { int i = 0xffff; while(i--) ; }
+static inline void mci_delay(void) { udelay(1000); }
 
 void INT_NAND(void)
 {
diff --git a/firmware/target/arm/as3525/system-target.h b/firmware/target/arm/as3525/system-target.h
index 1173515ebb..1ccd3282db 100644
--- a/firmware/target/arm/as3525/system-target.h
+++ b/firmware/target/arm/as3525/system-target.h
@@ -23,19 +23,76 @@
 
 #include "system-arm.h"
 #include "mmu-arm.h"
+#include "panic.h"
 
 #include "clock-target.h" /* CPUFREQ_* are defined here */
 
+#ifdef HAVE_SCROLLWHEEL
+/* let the timer interrupt twice as often for the scrollwheel polling */
+#define KERNEL_TIMER_FREQ (TIMER_FREQ/2)
+#else
+#define KERNEL_TIMER_FREQ TIMER_FREQ
+#endif
+
 #ifdef BOOTLOADER
 #define UNCACHED_ADDR(a) (a)
 #else
 #define UNCACHED_ADDR(a) ((typeof(a)) ((uintptr_t)(a) + 0x10000000))
 #endif
 
-
 #ifdef SANSA_C200V2
 /* 0: Backlight on A5, 1: Backlight on A7 */
 extern int c200v2_variant;
+/* c200v2 changes the timer interval often due to software pwm */
+#define TIMER_PERIOD TIMER2_BGLOAD
+#else
+#define TIMER_PERIOD (KERNEL_TIMER_FREQ/HZ)
 #endif
 
+/*
+ * This function is not overly accurate, so rather call it with an usec more
+ * than less (see below comment)
+ * 
+ * if inlined it expands to a really small and fast function if it's called
+ * with compile time constants */
+static inline void udelay(unsigned usecs) __attribute__((always_inline));
+static inline void udelay(unsigned usecs)
+{
+    int now, end;
+    
+    /**
+     * we're limited to 1.5us multiplies due to the odd timer frequency (1.5MHz),
+     * to avoid calculating which is safer (need to round up for small values)
+     * and saves spending time in the divider we have a lut for
+     * small us values, it should be roughly us*2/3
+     **/
+    static const unsigned char udelay_lut[] =
+    {
+        0, 1, 2, 2,  3,  4,  4,  5,  6,  6,
+        7, 8, 8, 9, 10, 10, 11, 12, 12, 13,
+    };
+
+
+    now = TIMER2_VALUE;
+    /* we don't want to handle multiple overflows, so limit the numbers
+     * (if you want to wait more than a tick just poll current_tick, or
+     * call sleep()) */
+    if (UNLIKELY(usecs >= TIMER_PERIOD))
+        panicf("%s(): %d too high!", __func__, usecs);
+    if (UNLIKELY(usecs <= 0))
+        return;
+    if (usecs < ARRAYLEN(udelay_lut))
+    {   /* the timer decrements */
+        end = now - udelay_lut[usecs];
+    }
+    else
+    {   /* to usecs */
+        int delay = usecs * 2 / 3; /* us * 1.5 = us*timer_period */
+        end = now - delay;
+    }
+    /* underrun ? */
+    if (end < 0)
+        end += TIMER_PERIOD;
+    while(TIMER2_VALUE != (unsigned)end);
+}
 #endif /* SYSTEM_TARGET_H */