g: Move chip pre-init to chip_pre_init()

Currently, chip/g uses jtag_pre_init() to do some chip
pre-initialization that isn't actually related to JTAG.  This has been
harmless, but it's currently the only chip which actually does "JTAG"
pre-init, and we'd like to get rid of that.  So, move that
functionality to a new optional chip_pre_init() function.

BUG=chromium:747629
BRANCH=cr50
TEST=make buildall
     boot cr50
     make all dis; confirm chip_pre_init() is called early in <main>

Change-Id: I3cae0747ab0c3cc974fce9f108947207b38e035f
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/629876
Reviewed-by: Mary Ruthven <mruthven@chromium.org>
Reviewed-by: Shawn N <shawnn@chromium.org>

chip/g/build.mk

@@ -20,7 +20,7 @@ CPPFLAGS += -I$(CRYPTOCLIB)/include
 endif
 
 # Required chip modules
-chip-y = clock.o gpio.o hwtimer.o jtag.o system.o
+chip-y = clock.o gpio.o hwtimer.o jtag.o pre_init.o system.o
 chip-$(CONFIG_BOARD_ID_SUPPORT) += board_id.o
 ifeq ($(CONFIG_POLLING_UART),y)
 chip-y += polling_uart.o

chip/g/config_chip.h

@@ -67,6 +67,9 @@
 /* We'll have some special commands of our own */
 #define CONFIG_EXTENSION_COMMAND 0xbaccd00a
 
+/* Chip needs to do custom pre-init */
+#define CONFIG_CHIP_PRE_INIT
+
 /*
  * The flash memory is implemented in two halves. The SoC bootrom will look for
  * the first-stage bootloader at the beginning of each of the two halves and

chip/g/jtag.c

@@ -3,28 +3,6 @@
  * found in the LICENSE file.
  */
 
-#include "registers.h"
-
 void jtag_pre_init(void)
 {
-	/*
-	 * We don't need to do anything for JTAG, but if we're resuming from
-	 * deep sleep we need to undo some stuff as soon as possible and this
-	 * is the first init function that's called.
-	 *
-	 * It doesn't hurt anything if this setup is not needed, but we don't
-	 * investigate the reset cause until much later (and doing so is
-	 * destructive), so we'll just do the post-deep-sleep setup every time.
-	 */
-
-	/* Disable the deep sleep triggers */
-	GR_PMU_LOW_POWER_DIS = 0;
-	GR_PMU_EXITPD_MASK = 0;
-
-	/* Unfreeze the USB module */
-	GWRITE_FIELD(USB, PCGCCTL, STOPPCLK, 0);
-	GWRITE_FIELD(USB, PCGCCTL, RSTPDWNMODULE, 0);
-	GWRITE_FIELD(USB, PCGCCTL, PWRCLMP, 0);
-
-
 }

chip/g/pre_init.c

@@ -0,0 +1,28 @@
+/* Copyright 2017 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "board_config.h"
+#include "registers.h"
+
+void chip_pre_init(void)
+{
+	/*
+	 * If we're resuming from deep sleep we need to undo some stuff as soon
+	 * as possible and this is the first init function that's called.
+	 *
+	 * It doesn't hurt anything if this setup is not needed, but we don't
+	 * investigate the reset cause until much later (and doing so is
+	 * destructive), so we'll just do the post-deep-sleep setup every time.
+	 */
+
+	/* Disable the deep sleep triggers */
+	GR_PMU_LOW_POWER_DIS = 0;
+	GR_PMU_EXITPD_MASK = 0;
+
+	/* Unfreeze the USB module */
+	GWRITE_FIELD(USB, PCGCCTL, STOPPCLK, 0);
+	GWRITE_FIELD(USB, PCGCCTL, RSTPDWNMODULE, 0);
+	GWRITE_FIELD(USB, PCGCCTL, PWRCLMP, 0);
+}

common/main.c

@@ -56,6 +56,10 @@ test_mockable __keep int main(void)
 	board_config_pre_init();
 #endif
 
+#ifdef CONFIG_CHIP_PRE_INIT
+	chip_pre_init();
+#endif
+
 #ifdef CONFIG_MPU
 	mpu_pre_init();
 #endif

include/board_config.h

@@ -1,6 +1,8 @@
 /* Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
+ *
+ * Extra hooks for board and chip initialization/configuration
  */
 
 #ifndef __CROS_EC_BOARD_CONFIG_H
@@ -48,4 +50,15 @@ void board_config_post_gpio_init(void);
 void board_before_rsmrst(int rsmrst);
 #endif
 
+/**
+ * Configure chip early in main(), just after board_config_pre_init().
+ *
+ * Most chip configuration is not particularly timing critical and can be done
+ * in other chip driver initialization such as system_pre_init() or HOOK_INIT
+ * handlers.  Chip pre-init should be reserved for small amounts of critical
+ * functionality that can't wait that long.  Think very hard before putting
+ * code here.
+ */
+void chip_pre_init(void);
+
 #endif /* __CROS_EC_BOARD_CONFIG_H */

include/config.h

@@ -616,6 +616,14 @@
 /* Enable trickle charging */
 #undef CONFIG_TRICKLE_CHARGING
 
+/*****************************************************************************/
+
+/*
+ * Chip needs to do pre-init very early in main(), and provides chip_pre_init()
+ * to do so.
+ */
+#undef CONFIG_CHIP_PRE_INIT
+
 /*****************************************************************************/
 /* Chipset config */