iPod Nano 2G: Dynamic Vcore scaling, based on current CPU clock. Adds 1-2 hours of battery life.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@28590 a1c6a512-1295-4272-9138-f99709370657

1 files changed, 8 insertions, 33 deletions

diff --git a/firmware/target/arm/s5l8700/system-s5l8700.c b/firmware/target/arm/s5l8700/system-s5l8700.c
index a0f671e298..e35da90617 100644
--- a/firmware/target/arm/s5l8700/system-s5l8700.c
+++ b/firmware/target/arm/s5l8700/system-s5l8700.c
@@ -203,16 +203,17 @@ void set_cpu_frequency(long frequency)
     if (cpu_frequency == frequency)
         return;
 
-    int oldlevel = disable_irq_save();
-
-#if 1
     if (frequency == CPUFREQ_MAX)
     {
+        /* Vcore = 1.000V */
+        pmu_write(0x1e, 0xf);
+        /* Allow for voltage to stabilize */
+        sleep(HZ / 100);
         /* FCLK_CPU = PLL0, HCLK = PLL0 / 2 */
         CLKCON = (CLKCON & ~0xFF00FF00) | 0x20003100;
         /* PCLK = HCLK / 2 */
         CLKCON2 |= 0x200;
-        /* Switch to ASYNCHRONOUS mode */
+        /* Switch to ASYNCHRONOUS mode => GCLK = FCLK_CPU */
         asm volatile(
             "mrc     p15, 0, r0,c1,c0    \n\t"
             "orr     r0, r0, #0xc0000000 \n\t"
@@ -222,7 +223,7 @@ void set_cpu_frequency(long frequency)
     }
     else
     {
-        /* Switch to FASTBUS mode */
+        /* Switch to FASTBUS mode => GCLK = HCLK */
         asm volatile(
             "mrc     p15, 0, r0,c1,c0    \n\t"
             "bic     r0, r0, #0xc0000000 \n\t"
@@ -233,37 +234,11 @@ void set_cpu_frequency(long frequency)
         CLKCON2 &= ~0x200;
         /* FCLK_CPU = OFF, HCLK = PLL0 / 4 */
         CLKCON = (CLKCON & ~0xFF00FF00) | 0x80003300;
+        /* Vcore = 0.900V */
+        pmu_write(0x1e, 0xb);
     }
 
-#else  /* Alternative: Also clock down the PLL. Doesn't seem to save much
-                       current, but results in high switching latency. */
-
-    if (frequency == CPUFREQ_MAX)
-    {
-        CLKCON &= ~0xFF00FF00;  /* Everything back to the OSC */
-        PLLCON &= ~1;  /* Power down PLL0 */
-        PLL0PMS = 0x021200;  /* 192 MHz */
-        PLL0LCNT = 8100;
-        PLLCON |= 1;  /* Power up PLL0 */
-        while (!(PLLLOCK & 1));  /* Wait for PLL to lock */
-        CLKCON2 |= 0x200;  /* PCLK = HCLK / 2 */
-        CLKCON |= 0x20003100;  /* FCLK_CPU = PLL0, PCLK = PLL0 / 2 */
-    }
-    else
-    {
-        CLKCON &= ~0xFF00FF00;  /* Everything back to the OSC */
-        CLKCON2 &= ~0x200;  /* PCLK = HCLK */
-        PLLCON &= ~1;  /* Power down PLL0 */
-        PLL0PMS = 0x000500;  /* 48 MHz */
-        PLL0LCNT = 8100;
-        PLLCON |= 1;  /* Power up PLL0 */
-        while (!(PLLLOCK & 1));  /* Wait for PLL to lock */
-        CLKCON |= 0x20002000;  /* FCLK_CPU = PLL0, PCLK = PLL0 */
-    }
-#endif
-
     cpu_frequency = frequency;
-    restore_irq(oldlevel);
 }
 
 #endif