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Classic/6G: CPU frequency/voltage scaling

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This patch implements HAVE_ADJUSTABLE_CPU_FREQ, it modifies the
following parameters when CPU is unboosted:

- s5l8702 voltage is decreased: 1.200V -> 1.050V
- CPU frequency is divided by 4: 216MHz -> 54MHz
- AHB frequency is divided by 2: 108MHz -> 54MHz

Change-Id: I2285b83efb7e1567864ac288f2d4ba55f058f7c5
This commit is contained in:
Cástor Muñoz 2012-03-21 00:02:25 +01:00
parent a75b5b83d4
commit a85780bacc
6 changed files with 48 additions and 6 deletions
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38
firmware/target/arm/s5l8702/system-s5l8702.c
View file

@ -255,16 +255,52 @@ void set_cpu_frequency(long frequency)
if (cpu_frequency == frequency)
return;
//TODO: Need to understand this better
/*
* CPU scaling parameters:
* CPUFREQ_MAX: CPU = 216MHz, AHB = 108MHz, Vcore = 1.200V
* CPUFREQ_NORMAL: CPU = 54MHz, AHB = 54MHz, Vcore = 1.050V
*
* CLKCON0 sets PLL2->FCLK divider (CPU clock)
* CLKCON1 sets FCLK->HCLK divider (AHB clock)
*
* HCLK is derived from FCLK, the system goes unstable if HCLK
* is out of the range 54-108 MHz, so two stages are required to
* switch FCLK (216 MHz <-> 54 MHz), adjusting HCLK in between
* to ensure system stability.
*/
if (frequency == CPUFREQ_MAX)
{
/* Vcore = 1.200V */
pmu_write(0x1e, 0x17);
/* FCLK = PLL2 / 2 (FCLK = 108MHz, HCLK = 108MHz) */
CLKCON0 = 0x3011;
udelay(50);
/* HCLK = FCLK / 2 (HCLK = 54MHz) */
CLKCON1 = 0x404101;
udelay(50);
/* FCLK = PLL2 (FCLK = 216MHz, HCLK = 108MHz) */
CLKCON0 = 0x3000;
udelay(100);
}
else
{
/* FCLK = PLL2 / 2 (FCLK = 108MHz, HCLK = 54MHz) */
CLKCON0 = 0x3011;
udelay(50);
/* HCLK = FCLK (HCLK = 108MHz) */
CLKCON1 = 0x4001;
udelay(50);
/* FCLK = PLL2 / 4 (FCLK = 54MHz, HCLK = 54MHz) */
CLKCON0 = 0x3013;
udelay(100);
/* Vcore = 1.050V */
pmu_write(0x1e, 0x11);
}
cpu_frequency = frequency;