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imx233: add function to change cpu/hbus frequency safely

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Change-Id: I88e9ad54ba65846ae4d94ae03009b3656f2489f2
This commit is contained in:
Amaury Pouly 2014-03-08 18:49:13 +01:00
parent 3e2f3efd89
commit 1f3979821c
2 changed files with 34 additions and 0 deletions
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32
firmware/target/arm/imx233/clkctrl-imx233.c
View file

@ -189,6 +189,38 @@ bool imx233_clkctrl_get_bypass(enum imx233_clock_t clk)
default: return false;
}
}
void imx233_clkctrl_set_cpu_hbus_div(int cpu_idiv, int cpu_fdiv, int hbus_div)
{
/* disable interrupts to avoid an IRQ being triggered at the point
* where we are slow/weird speeds, that would result in massive slow-down... */
int oldstatus = disable_interrupt_save(IRQ_FIQ_STATUS);
/* we need to be very careful here: putting the wrong dividers could blow-up the
* frequency and result in crash, also the cpu could be running from XTAL or
* PLL at this point */
int old_cpu_fdiv = imx233_clkctrl_get_frac_div(CLK_CPU);
int old_hbus_div = imx233_clkctrl_get_div(CLK_HBUS);
/* since HBUS is tied to cpu, we first ensure that the HBUS is safe to handle
* both old and new speed: take maximum of old and new dividers */
if(hbus_div > old_hbus_div)
imx233_clkctrl_set_div(CLK_HBUS, hbus_div);
/* we are about to change cpu speed: we first ensure that the fractional
* divider is safe to handle both old and new integer divided frequency: take max */
if(cpu_fdiv > old_cpu_fdiv)
imx233_clkctrl_set_frac_div(CLK_CPU, cpu_fdiv);
/* we are safe for major divider change */
imx233_clkctrl_set_div(CLK_CPU, cpu_idiv);
/* if the final fractional divider is lower than previous one, it's time to switch */
if(cpu_fdiv < old_cpu_fdiv)
imx233_clkctrl_set_frac_div(CLK_CPU, cpu_fdiv);
/* if we were running from XTAL, switch to PLL */
imx233_clkctrl_set_bypass(CLK_CPU, false);
/* finally restore HBUS to its proper value */
if(hbus_div < old_hbus_div)
imx233_clkctrl_set_div(CLK_HBUS, hbus_div);
/* we are free again */
restore_interrupt(oldstatus);
}
#endif
void imx233_clkctrl_enable_usb(bool enable)

2
firmware/target/arm/imx233/clkctrl-imx233.h
View file

@ -72,6 +72,8 @@ void imx233_clkctrl_set_frac_div(enum imx233_clock_t clk, int fracdiv);
int imx233_clkctrl_get_frac_div(enum imx233_clock_t clk);
void imx233_clkctrl_set_bypass(enum imx233_clock_t clk, bool bypass);
bool imx233_clkctrl_get_bypass(enum imx233_clock_t clk);
/* all-in-one function which handle all quirks */
void imx233_clkctrl_set_cpu_hbus_div(int cpu_idiv, int cpu_fdiv, int hbus_div);
#endif
void imx233_clkctrl_enable_usb(bool enable);
bool imx233_clkctrl_is_usb_enabled(void);