Enable PLL only briefly during ADC init

It was previously only enabled for 1500us during boot, but in a way
that triggered a needless round of notifications to other modules.
This is cleaner.

This also fixes adc_init() not initializing the task IDs to wake when
interrupts come in, and removes some unneeded code from other init
functions.

BUG=chrome-os-partner:12472
TEST=boot system and run adc command.  Should still provide reasonable data.

Change-Id: I9ae5857d988c727caf5d53f551a2f12b30974c0f
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/29806
Reviewed-by: Bill Richardson <wfrichar@chromium.org>

4 files changed, 58 insertions, 34 deletions

diff --git a/chip/lm4/adc.c b/chip/lm4/adc.c
index 03516a5eb3..57604d1204 100644
--- a/chip/lm4/adc.c
+++ b/chip/lm4/adc.c
@@ -6,6 +6,7 @@
 /* LM4-specific ADC module for Chrome EC */
 
 #include "adc.h"
+#include "clock.h"
 #include "console.h"
 #include "gpio.h"
 #include "hooks.h"
@@ -51,11 +52,6 @@ const uint32_t ain_port[24][2] = {
 static void configure_gpio(void)
 {
 	int i;
-	volatile uint32_t scratch  __attribute__((unused));
-
-	/* Enable GPIOE module and delay a few clocks */
-	LM4_SYSTEM_RCGCGPIO |= 0x0010;
-	scratch = LM4_SYSTEM_RCGCGPIO;
 
 	/* Use analog function for AIN */
 	for (i = 0; i < ADC_CH_COUNT; ++i) {
@@ -114,22 +110,22 @@ int lm4_adc_configure(enum lm4_adc_sequencer seq,
 		      int ain_id,
 		      int ssctl)
 {
-	volatile uint32_t scratch  __attribute__((unused));
-	/* TODO: set up clock using ADCCC register? */
 	/* Configure sample sequencer */
 	LM4_ADC_ADCACTSS &= ~(0x01 << seq);
+
 	/* Trigger sequencer by processor request */
 	LM4_ADC_ADCEMUX = (LM4_ADC_ADCEMUX & ~(0xf << (seq * 4))) | 0x00;
+
 	/* Sample internal temp sensor */
 	if (ain_id != LM4_AIN_NONE) {
 		LM4_ADC_SSMUX(seq) = ain_id & 0xf;
 		LM4_ADC_SSEMUX(seq) = ain_id >> 4;
-	}
-	else {
+	} else {
 		LM4_ADC_SSMUX(seq) = 0x00;
 		LM4_ADC_SSEMUX(seq) = 0x00;
 	}
 	LM4_ADC_SSCTL(seq) = ssctl;
+
 	/* Enable sample sequencer */
 	LM4_ADC_ADCACTSS |= 0x01 << seq;
 
@@ -214,20 +210,36 @@ static int adc_init(void)
 	int i;
 	const struct adc_t *adc;
 
-        /* Enable ADC0 module and delay a few clocks */
-	LM4_SYSTEM_RCGCADC |= 0x01;
-	udelay(1);
-
 	/* Configure GPIOs */
 	configure_gpio();
 
-	/* Use external voltage references (VREFA+, VREFA-) instead of
-	 * VDDA and GNDA. */
+	/*
+	 * Temporarily enable the PLL when turning on the clock to the ADC
+	 * module, to work around chip errata (10.4).  No need to notify
+	 * other modules; the PLL isn't enabled long enough to matter.
+	 */
+	clock_enable_pll(1, 0);
+
+	/* Enable ADC0 module and delay a few clocks. */
+	LM4_SYSTEM_RCGCADC = 1;
+	clock_wait_cycles(3);
+
+	/*
+	 * Use external voltage references (VREFA+, VREFA-) instead of
+	 * VDDA and GNDA.
+	 */
 	LM4_ADC_ADCCTL = 0x01;
 
 	/* Use internal oscillator */
 	LM4_ADC_ADCCC = 0x1;
 
+	/* Disable the PLL now that the ADC is using the internal oscillator */
+	clock_enable_pll(0, 0);
+
+	/* No tasks waiting yet */
+	for (i = 0; i < LM4_ADC_SEQ_COUNT; i++)
+		task_waiting_on_ss[i] = TASK_ID_INVALID;
+
 	/* Enable interrupt */
 	LM4_ADC_ADCIM = 0xF;
 	task_enable_irq(LM4_IRQ_ADC0_SS0);
diff --git a/chip/lm4/clock.c b/chip/lm4/clock.c
index 6031767872..65dc62d069 100644
--- a/chip/lm4/clock.c
+++ b/chip/lm4/clock.c
@@ -64,7 +64,7 @@ static void enable_pll(void)
 }
 
 
-int clock_enable_pll(int enable)
+int clock_enable_pll(int enable, int notify)
 {
 	if (enable)
 		enable_pll();
@@ -72,7 +72,7 @@ int clock_enable_pll(int enable)
 		disable_pll();
 
 	/* Notify modules of frequency change */
-	return hook_notify(HOOK_FREQ_CHANGE, 0);
+	return notify ? hook_notify(HOOK_FREQ_CHANGE, 0) : EC_SUCCESS;
 }
 
 
@@ -211,9 +211,9 @@ static int command_pll(int argc, char **argv)
 	/* Toggle the PLL */
 	if (argc > 1) {
 		if (!strcasecmp(argv[1], "off"))
-			clock_enable_pll(0);
+			clock_enable_pll(0, 1);
 		else if (!strcasecmp(argv[1], "on"))
-			clock_enable_pll(1);
+			clock_enable_pll(1, 1);
 		else {
 			/* Disable PLL and set extra divider */
 			char *e;
@@ -279,8 +279,8 @@ int clock_init(void)
 	if (!system_jumped_to_this_image())
 		clock_wait_cycles(500000);
 
-	/* Start out with PLL enabled */
-	enable_pll();
+	/* Make sure PLL is disabled */
+	disable_pll();
 
 	return EC_SUCCESS;
 }
diff --git a/common/main.c b/common/main.c
index 79ad7bfac2..22906cb7be 100644
--- a/common/main.c
+++ b/common/main.c
@@ -52,7 +52,7 @@ int main(void)
 
 #ifdef CONFIG_FLASH
 	/*
-	 * Initialize flash and apply write protecte if necessary.  Requires
+	 * Initialize flash and apply write protect if necessary.  Requires
 	 * the reset flags calculated by system initialization.
 	 */
 	flash_pre_init();
@@ -121,10 +121,6 @@ int main(void)
 	 */
 	hook_notify(HOOK_INIT, 0);
 
-#ifdef BOARD_link
-	/* Reduce core clock now that init is done */
-	clock_enable_pll(0);
-#endif
 	/*
 	 * Print the init time.  Not completely accurate because it can't take
 	 * into account the time before timer_init(), but it'll at least catch
diff --git a/include/clock.h b/include/clock.h
index c28dbb1bf2..1d2506029d 100644
--- a/include/clock.h
+++ b/include/clock.h
@@ -3,24 +3,40 @@
  * found in the LICENSE file.
  */
 
-/*  Clocks and power management settings */
+/* Clocks and power management settings */
 
 #ifndef __CROS_EC_CLOCK_H
 #define __CROS_EC_CLOCK_H
 
 #include "common.h"
 
-/* Set the CPU clocks and PLLs. */
+/**
+ * Set the CPU clocks and PLLs.
+ */
 int clock_init(void);
 
-/* Return the current clock frequency in Hz. */
+/**
+ * Return the current clock frequency in Hz.
+ */
 int clock_get_freq(void);
 
-/* Enable or disable the PLL. */
-int clock_enable_pll(int enable);
-
-/* Wait <cycles> system clock cycles.  Simple busy waiting for before
- * clocks/timers are initialized. */
+/**
+ * Enable or disable the PLL.
+ *
+ * @param enable	Enable PLL if non-zero; disable if zero.
+ * @param notify	Notify other modules of the PLL change.  This should
+ *			be 1 unless you're briefly turning on the PLL to work
+ *			around a chip errata at init time.
+ */
+int clock_enable_pll(int enable, int notify);
+
+/**
+ * Wait for a number of clock cycles.
+ *
+ * Simple busy waiting for use before clocks/timers are initialized.
+ *
+ * @param cycles	Number of cycles to wait.
+ */
 void clock_wait_cycles(uint32_t cycles);
 
 /* Low power modes for idle API */