[U-Boot] [PATCH 2/5] ARM: mxs: Document the power block initialization
Marek Vasut
marex at denx.de
Sat Aug 31 15:53:43 CEST 2013
This patch adds documentation for the functions used during the
initialization of MXS power block.
Signed-off-by: Marek Vasut <marex at denx.de>
Cc: Fabio Estevam <fabio.estevam at freescale.com>
Cc: Stefano Babic <sbabic at denx.de>
---
arch/arm/cpu/arm926ejs/mxs/spl_power_init.c | 208 +++++++++++++++++++++++++++
1 file changed, 208 insertions(+)
diff --git a/arch/arm/cpu/arm926ejs/mxs/spl_power_init.c b/arch/arm/cpu/arm926ejs/mxs/spl_power_init.c
index e3b6cd9..32f6e53 100644
--- a/arch/arm/cpu/arm926ejs/mxs/spl_power_init.c
+++ b/arch/arm/cpu/arm926ejs/mxs/spl_power_init.c
@@ -14,6 +14,13 @@
#include "mxs_init.h"
+/**
+ * mxs_power_clock2xtal() - Switch CPU core clock source to 24MHz XTAL
+ *
+ * This function switches the CPU core clock from PLL to 24MHz XTAL
+ * oscilator. This is necessary if the PLL is being reconfigured to
+ * prevent crash of the CPU core.
+ */
static void mxs_power_clock2xtal(void)
{
struct mxs_clkctrl_regs *clkctrl_regs =
@@ -24,6 +31,13 @@ static void mxs_power_clock2xtal(void)
&clkctrl_regs->hw_clkctrl_clkseq_set);
}
+/**
+ * mxs_power_clock2pll() - Switch CPU core clock source to PLL
+ *
+ * This function switches the CPU core clock from 24MHz XTAL oscilator
+ * to PLL. This can only be called once the PLL has re-locked and once
+ * the PLL is stable after reconfiguration.
+ */
static void mxs_power_clock2pll(void)
{
struct mxs_clkctrl_regs *clkctrl_regs =
@@ -36,6 +50,12 @@ static void mxs_power_clock2pll(void)
CLKCTRL_CLKSEQ_BYPASS_CPU);
}
+/**
+ * mxs_power_clear_auto_restart() - Set the auto-restart bit
+ *
+ * This function ungates the RTC block and sets the AUTO_RESTART
+ * bit to work around a design bug on MX28EVK Rev. A .
+ */
static void mxs_power_clear_auto_restart(void)
{
struct mxs_rtc_regs *rtc_regs =
@@ -69,6 +89,14 @@ static void mxs_power_clear_auto_restart(void)
;
}
+/**
+ * mxs_power_set_linreg() - Set linear regulators 25mV below DC-DC converter
+ *
+ * This function configures the VDDIO, VDDA and VDDD linear regulators output
+ * to be 25mV below the VDDIO, VDDA and VDDD output from the DC-DC switching
+ * converter. This is the recommended setting for the case where we use both
+ * linear regulators and DC-DC converter to power the VDDIO rail.
+ */
static void mxs_power_set_linreg(void)
{
struct mxs_power_regs *power_regs =
@@ -88,6 +116,11 @@ static void mxs_power_set_linreg(void)
POWER_VDDIOCTRL_LINREG_OFFSET_1STEPS_BELOW);
}
+/**
+ * mxs_get_batt_volt() - Measure battery input voltage
+ *
+ * This function retrieves the battery input voltage and returns it.
+ */
static int mxs_get_batt_volt(void)
{
struct mxs_power_regs *power_regs =
@@ -99,11 +132,24 @@ static int mxs_get_batt_volt(void)
return volt;
}
+/**
+ * mxs_is_batt_ready() - Test if the battery provides enough voltage to boot
+ *
+ * This function checks if the battery input voltage is higher than 3.6V and
+ * therefore allows the system to successfully boot using this power source.
+ */
static int mxs_is_batt_ready(void)
{
return (mxs_get_batt_volt() >= 3600);
}
+/**
+ * mxs_is_batt_good() - Test if battery is operational at all
+ *
+ * This function starts recharging the battery and tests if the input current
+ * provided by the 5V input recharging the battery is also sufficient to power
+ * the DC-DC converter.
+ */
static int mxs_is_batt_good(void)
{
struct mxs_power_regs *power_regs =
@@ -144,6 +190,15 @@ static int mxs_is_batt_good(void)
return 0;
}
+/**
+ * mxs_power_setup_5v_detect() - Start the 5V input detection comparator
+ *
+ * This function enables the 5V detection comparator and sets the 5V valid
+ * threshold to 4.4V . We use 4.4V threshold here to make sure that even
+ * under high load, the voltage drop on the 5V input won't be so critical
+ * to cause undervolt on the 4P2 linear regulator supplying the DC-DC
+ * converter and thus making the system crash.
+ */
static void mxs_power_setup_5v_detect(void)
{
struct mxs_power_regs *power_regs =
@@ -156,6 +211,12 @@ static void mxs_power_setup_5v_detect(void)
POWER_5VCTRL_PWRUP_VBUS_CMPS);
}
+/**
+ * mxs_src_power_init() - Preconfigure the power block
+ *
+ * This function configures reasonable values for the DC-DC control loop
+ * and battery monitor.
+ */
static void mxs_src_power_init(void)
{
struct mxs_power_regs *power_regs =
@@ -187,6 +248,12 @@ static void mxs_src_power_init(void)
clrbits_le32(&power_regs->hw_power_5vctrl, POWER_5VCTRL_DCDC_XFER);
}
+/**
+ * mxs_power_init_4p2_params() - Configure the parameters of the 4P2 regulator
+ *
+ * This function configures the necessary parameters for the 4P2 linear
+ * regulator to supply the DC-DC converter from 5V input.
+ */
static void mxs_power_init_4p2_params(void)
{
struct mxs_power_regs *power_regs =
@@ -211,6 +278,12 @@ static void mxs_power_init_4p2_params(void)
0x3f << POWER_5VCTRL_CHARGE_4P2_ILIMIT_OFFSET);
}
+/**
+ * mxs_enable_4p2_dcdc_input() - Enable or disable the DCDC input from 4P2
+ * @xfer: Select if the input shall be enabled or disabled
+ *
+ * This function enables or disables the 4P2 input into the DC-DC converter.
+ */
static void mxs_enable_4p2_dcdc_input(int xfer)
{
struct mxs_power_regs *power_regs =
@@ -307,6 +380,12 @@ static void mxs_enable_4p2_dcdc_input(int xfer)
POWER_CTRL_ENIRQ_VDD5V_DROOP);
}
+/**
+ * mxs_power_init_4p2_regulator() - Start the 4P2 regulator
+ *
+ * This function enables the 4P2 regulator and switches the DC-DC converter
+ * to use the 4P2 input.
+ */
static void mxs_power_init_4p2_regulator(void)
{
struct mxs_power_regs *power_regs =
@@ -391,6 +470,12 @@ static void mxs_power_init_4p2_regulator(void)
writel(POWER_CTRL_DCDC4P2_BO_IRQ, &power_regs->hw_power_ctrl_clr);
}
+/**
+ * mxs_power_init_dcdc_4p2_source() - Switch DC-DC converter to 4P2 source
+ *
+ * This function configures the DC-DC converter to be supplied from the 4P2
+ * linear regulator.
+ */
static void mxs_power_init_dcdc_4p2_source(void)
{
struct mxs_power_regs *power_regs =
@@ -413,6 +498,12 @@ static void mxs_power_init_dcdc_4p2_source(void)
}
}
+/**
+ * mxs_power_enable_4p2() - Power up the 4P2 regulator
+ *
+ * This function drives the process of powering up the 4P2 linear regulator
+ * and switching the DC-DC converter input over to the 4P2 linear regulator.
+ */
static void mxs_power_enable_4p2(void)
{
struct mxs_power_regs *power_regs =
@@ -472,6 +563,14 @@ static void mxs_power_enable_4p2(void)
&power_regs->hw_power_charge_clr);
}
+/**
+ * mxs_boot_valid_5v() - Boot from 5V supply
+ *
+ * This function configures the power block to boot from valid 5V input.
+ * This is called only if the 5V is reliable and can properly supply the
+ * CPU. This function proceeds to configure the 4P2 converter to be supplied
+ * from the 5V input.
+ */
static void mxs_boot_valid_5v(void)
{
struct mxs_power_regs *power_regs =
@@ -495,6 +594,11 @@ static void mxs_boot_valid_5v(void)
mxs_power_enable_4p2();
}
+/**
+ * mxs_powerdown() - Shut down the system
+ *
+ * This function powers down the CPU completely.
+ */
static void mxs_powerdown(void)
{
struct mxs_power_regs *power_regs =
@@ -504,6 +608,12 @@ static void mxs_powerdown(void)
&power_regs->hw_power_reset);
}
+/**
+ * mxs_batt_boot() - Configure the power block to boot from battery input
+ *
+ * This function configures the power block to boot from the battery voltage
+ * supply.
+ */
static void mxs_batt_boot(void)
{
struct mxs_power_regs *power_regs =
@@ -548,6 +658,14 @@ static void mxs_batt_boot(void)
0x8 << POWER_5VCTRL_CHARGE_4P2_ILIMIT_OFFSET);
}
+/**
+ * mxs_handle_5v_conflict() - Test if the 5V input is reliable
+ *
+ * This function tests if the 5V input can reliably supply the system. If it
+ * can, then proceed to configuring the system to boot from 5V source, otherwise
+ * try booting from battery supply. If we can not boot from battery supply
+ * either, shut down the system.
+ */
static void mxs_handle_5v_conflict(void)
{
struct mxs_power_regs *power_regs =
@@ -584,6 +702,12 @@ static void mxs_handle_5v_conflict(void)
}
}
+/**
+ * mxs_5v_boot() - Configure the power block to boot from 5V input
+ *
+ * This function handles configuration of the power block when supplied by
+ * a 5V input.
+ */
static void mxs_5v_boot(void)
{
struct mxs_power_regs *power_regs =
@@ -607,6 +731,12 @@ static void mxs_5v_boot(void)
mxs_handle_5v_conflict();
}
+/**
+ * mxs_init_batt_bo() - Configure battery brownout threshold
+ *
+ * This function configures the battery input brownout threshold. The value
+ * at which the battery brownout happens is configured to 3.0V in the code.
+ */
static void mxs_init_batt_bo(void)
{
struct mxs_power_regs *power_regs =
@@ -621,6 +751,12 @@ static void mxs_init_batt_bo(void)
writel(POWER_CTRL_ENIRQ_BATT_BO, &power_regs->hw_power_ctrl_clr);
}
+/**
+ * mxs_switch_vddd_to_dcdc_source() - Switch VDDD rail to DC-DC converter
+ *
+ * This function turns off the VDDD linear regulator and therefore makes
+ * the VDDD rail be supplied only by the DC-DC converter.
+ */
static void mxs_switch_vddd_to_dcdc_source(void)
{
struct mxs_power_regs *power_regs =
@@ -635,6 +771,15 @@ static void mxs_switch_vddd_to_dcdc_source(void)
POWER_VDDDCTRL_DISABLE_STEPPING);
}
+/**
+ * mxs_power_configure_power_source() - Configure power block source
+ *
+ * This function is the core of the power configuration logic. The function
+ * selects the power block input source and configures the whole power block
+ * accordingly. After the configuration is complete and the system is stable
+ * again, the function switches the CPU clock source back to PLL. Finally,
+ * the function switches the voltage rails to DC-DC converter.
+ */
static void mxs_power_configure_power_source(void)
{
int batt_ready, batt_good;
@@ -679,6 +824,15 @@ static void mxs_power_configure_power_source(void)
#endif
}
+/**
+ * mxs_enable_output_rail_protection() - Enable power rail protection
+ *
+ * This function enables overload protection on the power rails. This is
+ * triggered if the power rails' voltage drops rapidly due to overload and
+ * in such case, the supply to the powerrail is cut-off, protecting the
+ * CPU from damage. Note that under such condition, the system will likely
+ * crash or misbehave.
+ */
static void mxs_enable_output_rail_protection(void)
{
struct mxs_power_regs *power_regs =
@@ -697,6 +851,13 @@ static void mxs_enable_output_rail_protection(void)
POWER_VDDIOCTRL_PWDN_BRNOUT);
}
+/**
+ * mxs_get_vddio_power_source_off() - Get VDDIO rail power source
+ *
+ * This function tests if the VDDIO rail is supplied by linear regulator
+ * or by the DC-DC converter. Returns 1 if powered by linear regulator,
+ * returns 0 if powered by the DC-DC converter.
+ */
static int mxs_get_vddio_power_source_off(void)
{
struct mxs_power_regs *power_regs =
@@ -725,6 +886,13 @@ static int mxs_get_vddio_power_source_off(void)
}
+/**
+ * mxs_get_vddd_power_source_off() - Get VDDD rail power source
+ *
+ * This function tests if the VDDD rail is supplied by linear regulator
+ * or by the DC-DC converter. Returns 1 if powered by linear regulator,
+ * returns 0 if powered by the DC-DC converter.
+ */
static int mxs_get_vddd_power_source_off(void)
{
struct mxs_power_regs *power_regs =
@@ -813,6 +981,18 @@ static const struct mxs_vddx_cfg mxs_vddmem_cfg = {
};
#endif
+/**
+ * mxs_power_set_vddx() - Configure voltage on DC-DC converter rail
+ * @cfg: Configuration data of the DC-DC converter rail
+ * @new_target: New target voltage of the DC-DC converter rail
+ * @new_brownout: New brownout trigger voltage
+ *
+ * This function configures the output voltage on the DC-DC converter rail.
+ * The rail is selected by the @cfg argument. The new voltage target is
+ * selected by the @new_target and the voltage is specified in mV. The
+ * new brownout value is selected by the @new_brownout argument and the
+ * value is also in mV.
+ */
static void mxs_power_set_vddx(const struct mxs_vddx_cfg *cfg,
uint32_t new_target, uint32_t new_brownout)
{
@@ -886,6 +1066,14 @@ static void mxs_power_set_vddx(const struct mxs_vddx_cfg *cfg,
}
}
+/**
+ * mxs_setup_batt_detect() - Start the battery voltage measurement logic
+ *
+ * This function starts and configures the LRADC block. This allows the
+ * power initialization code to measure battery voltage and based on this
+ * knowledge, decide whether to boot at all, boot from battery or boot
+ * from 5V input.
+ */
static void mxs_setup_batt_detect(void)
{
mxs_lradc_init();
@@ -893,6 +1081,14 @@ static void mxs_setup_batt_detect(void)
early_delay(10);
}
+/**
+ * mxs_ungate_power() - Ungate the POWER block
+ *
+ * This function ungates clock to the power block. In case the power block
+ * was still gated at this point, it will not be possible to configure the
+ * block and therefore the power initialization would fail. This function
+ * is only needed on i.MX233, on i.MX28 the power block is always ungated.
+ */
static void mxs_ungate_power(void)
{
#ifdef CONFIG_MX23
@@ -903,6 +1099,12 @@ static void mxs_ungate_power(void)
#endif
}
+/**
+ * mxs_power_init() - The power block init main function
+ *
+ * This function calls all the power block initialization functions in
+ * proper sequence to start the power block.
+ */
void mxs_power_init(void)
{
struct mxs_power_regs *power_regs =
@@ -936,6 +1138,12 @@ void mxs_power_init(void)
}
#ifdef CONFIG_SPL_MXS_PSWITCH_WAIT
+/**
+ * mxs_power_wait_pswitch() - Wait for power switch to be pressed
+ *
+ * This function waits until the power-switch was pressed to start booting
+ * the board.
+ */
void mxs_power_wait_pswitch(void)
{
struct mxs_power_regs *power_regs =
--
1.7.10.4
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