Change in coreboot[master]: mb/google/corsola: Get RAM code from ADC

[Rex-BC Chen (Code Review)]

Rex-BC Chen has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/59570 )

Change subject: mb/google/corsola: Get RAM code from ADC
......................................................................

mb/google/corsola: Get RAM code from ADC

On Chromebooks the RAM code is implemented by the resistor straps
that we can read and decode from ADC. For Corsola the RAM code can be
read from ADC channel 2 and 3.

TEST=build pass
BUG=b:202871018

Signed-off-by: Rex-BC Chen 
Change-Id: I485c32dec7b425b604b4063d742a0e37d3961513
---
M src/mainboard/google/corsola/Makefile.inc
A src/mainboard/google/corsola/boardid.c
2 files changed, 70 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/70/59570/1

diff --git a/src/mainboard/google/corsola/Makefile.inc b/src/mainboard/google/corsola/Makefile.inc
index 7995f8a..1a9a1c28 100644
--- a/src/mainboard/google/corsola/Makefile.inc
+++ b/src/mainboard/google/corsola/Makefile.inc
@@ -7,11 +7,13 @@
 verstage-y += reset.c

romstage-y += memlayout.ld
+romstage-y += boardid.c
 romstage-y += chromeos.c
 romstage-y += regulator.c
 romstage-y += romstage.c

ramstage-y += memlayout.ld
+ramstage-y += boardid.c
 ramstage-y += chromeos.c
 ramstage-y += mainboard.c
 ramstage-y += regulator.c
diff --git a/src/mainboard/google/corsola/boardid.c b/src/mainboard/google/corsola/boardid.c
new file mode 100644
index 0000000..285b065
--- /dev/null
+++ b/src/mainboard/google/corsola/boardid.c
@@ -0,0 +1,68 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <assert.h>
+#include <boardid.h>
+#include <console/console.h>
+#include <soc/auxadc.h>
+
+/* board_id is provided by ec/google/chromeec/ec_boardid.c */
+
+#define ADC_LEVELS 12
+
+enum {
+	/* RAM IDs */
+	RAM_ID_LOW_CHANNEL = 2,
+	RAM_ID_HIGH_CHANNEL = 3,
+};
+
+static const unsigned int ram_voltages[ADC_LEVELS] = {
+	/* ID : Voltage (unit: uV) */
+	[0]  =   74300,
+	[1]  =  211700,
+	[2]  =  318800,
+	[3]  =  428600,
+	[4]  =  541700,
+	[5]  =  665800,
+	[6]  =  781400,
+	[7]  =  900000,
+	[8]  = 1023100,
+	[9]  = 1137000,
+	[10] = 1240000,
+	[11] = 1342600,
+};
+
+static const unsigned int *adc_voltages[] = {
+	[RAM_ID_LOW_CHANNEL] = ram_voltages,
+	[RAM_ID_HIGH_CHANNEL] = ram_voltages,
+};
+
+static uint32_t get_adc_index(unsigned int channel)
+{
+	unsigned int value = auxadc_get_voltage_uv(channel);
+
+	assert(channel < ARRAY_SIZE(adc_voltages));
+	const unsigned int *voltages = adc_voltages[channel];
+	assert(voltages);
+
+	/* Find the closest voltage */
+	uint32_t id;
+	for (id = 0; id < ADC_LEVELS - 1; id++)
+		if (value < (voltages[id] + voltages[id + 1]) / 2)
+			break;
+
+	printk(BIOS_DEBUG, "ADC[%u]: Raw value=%u ID=%u\n", channel, value, id);
+	return id;
+}
+
+uint32_t ram_code(void)
+{
+	static uint32_t cached_ram_code = BOARD_ID_INIT;
+
+	if (cached_ram_code == BOARD_ID_INIT) {
+		cached_ram_code = (get_adc_index(RAM_ID_HIGH_CHANNEL) << 4 |
+				   get_adc_index(RAM_ID_LOW_CHANNEL));
+		printk(BIOS_DEBUG, "RAM Code: %#02x\n", cached_ram_code);
+	}
+
+	return cached_ram_code;
+}