arm, am335x: Enable Spread Spectrum for the MPU

Enable Spread Spectrum for the MPU by calculating the required
values and setting the registers accordingly.

Signed-off-by: Heiko Schocher <hs@denx.de>
Reviewed-by: Tom Rini <trini@konsulko.com>
This commit is contained in:
Heiko Schocher 2016-06-07 08:31:19 +02:00 committed by Tom Rini
parent c01bc75e7d
commit 694607b563
3 changed files with 76 additions and 1 deletions

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@ -159,3 +159,76 @@ void enable_basic_clocks(void)
/* Select the Master osc 24 MHZ as Timer2 clock source */
writel(0x1, &cmdpll->clktimer2clk);
}
/*
* Enable Spread Spectrum for the MPU by calculating the required
* values and setting the registers accordingly.
* @param permille The spreading in permille (10th of a percent)
*/
void set_mpu_spreadspectrum(int permille)
{
u32 multiplier_m;
u32 predivider_n;
u32 cm_clksel_dpll_mpu;
u32 cm_clkmode_dpll_mpu;
u32 ref_clock;
u32 pll_bandwidth;
u32 mod_freq_divider;
u32 exponent;
u32 mantissa;
u32 delta_m_step;
printf("Enabling Spread Spectrum of %d permille for MPU\n",
permille);
/* Read PLL parameter m and n */
cm_clksel_dpll_mpu = readl(&cmwkup->clkseldpllmpu);
multiplier_m = (cm_clksel_dpll_mpu >> 8) & 0x3FF;
predivider_n = cm_clksel_dpll_mpu & 0x7F;
/*
* Calculate reference clock (clock after pre-divider),
* its max. PLL bandwidth,
* and resulting mod_freq_divider
*/
ref_clock = V_OSCK / (predivider_n + 1);
pll_bandwidth = ref_clock / 70;
mod_freq_divider = ref_clock / (4 * pll_bandwidth);
/* Calculate Mantissa/Exponent */
exponent = 0;
mantissa = mod_freq_divider;
while ((mantissa > 127) && (exponent < 7)) {
exponent++;
mantissa /= 2;
}
if (mantissa > 127)
mantissa = 127;
mod_freq_divider = mantissa << exponent;
/*
* Calculate Modulation steps
* As we use Downspread only, the spread is twice the value of
* permille, so Div2!
* As it takes the value in percent, divide by ten!
*/
delta_m_step = ((u32)((multiplier_m * permille) / 10 / 2)) << 18;
delta_m_step /= 100;
delta_m_step /= mod_freq_divider;
if (delta_m_step > 0xFFFFF)
delta_m_step = 0xFFFFF;
/* Setup Spread Spectrum */
writel(delta_m_step, &cmwkup->sscdeltamstepdllmpu);
writel((exponent << 8) | mantissa, &cmwkup->sscmodfreqdivdpllmpu);
cm_clkmode_dpll_mpu = readl(&cmwkup->clkmoddpllmpu);
/* clear all SSC flags */
cm_clkmode_dpll_mpu &= ~(0xF << CM_CLKMODE_DPLL_SSC_EN_SHIFT);
/* enable SSC with Downspread only */
cm_clkmode_dpll_mpu |= CM_CLKMODE_DPLL_SSC_EN_MASK |
CM_CLKMODE_DPLL_SSC_DOWNSPREAD_MASK;
writel(cm_clkmode_dpll_mpu, &cmwkup->clkmoddpllmpu);
while (!(readl(&cmwkup->clkmoddpllmpu) & 0x2000))
;
}

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@ -117,4 +117,5 @@ void enable_basic_clocks(void);
void do_enable_clocks(u32 *const *, u32 *const *, u8);
void do_disable_clocks(u32 *const *, u32 *const *, u8);
void set_mpu_spreadspectrum(int permille);
#endif

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@ -99,7 +99,8 @@ struct cm_wkuppll {
unsigned int timer0clkctrl; /* offset 0x10 */
unsigned int resv2[3];
unsigned int idlestdpllmpu; /* offset 0x20 */
unsigned int resv3[2];
unsigned int sscdeltamstepdllmpu; /* off 0x24 */
unsigned int sscmodfreqdivdpllmpu; /* off 0x28 */
unsigned int clkseldpllmpu; /* offset 0x2c */
unsigned int resv4[1];
unsigned int idlestdpllddr; /* offset 0x34 */