From f91f18cdc4f7bf5f1a552d54218084928b2eeb06 Mon Sep 17 00:00:00 2001
From: Nick Vaccaro <nvaccaro@google.com>
Date: Wed, 21 Jan 2026 13:56:36 -0800
Subject: [PATCH] mb/goog/ocelot/var/ocelot: add LPSS touchscreen support for
 Rex Touchscreen

Support for the rex touchscreen panel was needed for the RVP to validate touchscreen functionality. The LPSS touchscreen is mapped to I2C bus 4 and the rex panel is mapped to address 0x10.

BUG=b:458429110
TEST=None

Change-Id: I99b2c7beaab63da1877995c655ff8eddf9c3a69f
Signed-off-by: Avi Uday <aviuday@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/90859
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Pranava Y N <pranavayn@google.com>
---
 .../google/ocelot/variants/ocelot/fw_config.c | 23 +++++++++++++++
 .../ocelot/variants/ocelot/overridetree.cb    | 28 ++++++++++++++++++-
 2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/src/mainboard/google/ocelot/variants/ocelot/fw_config.c b/src/mainboard/google/ocelot/variants/ocelot/fw_config.c
index d9f68ab505..003cd84728 100644
--- a/src/mainboard/google/ocelot/variants/ocelot/fw_config.c
+++ b/src/mainboard/google/ocelot/variants/ocelot/fw_config.c
@@ -292,6 +292,27 @@ static const struct pad_config touchscreen_disable_pads[] = {
 	PAD_NC(GPP_VGPIO3_THC0, NONE),
 };
 
+static const struct pad_config touchscreen_lpss_i2c_enable_pads[] = {
+	/* GPP_E11:     THC0_SPI1_CLK_TCH_PNL1 */
+	PAD_NC(GPP_E11, NONE),
+	/* GPP_E12:     THC0_SPI1_IO_0_I2C4_SCL_TCH_PNL1 NF1: THC I2C0_SCL */
+	PAD_CFG_NF(GPP_E12, NONE, DEEP, NF8),
+	/* GPP_E13:     THC0_SPI1_IO_1_I2C4_SDA_TCH_PNL1 NF1: THC I2C0 SDA */
+	PAD_CFG_NF(GPP_E13, NONE, DEEP, NF8),
+	/* GPP_E14:     THC0_SPI1_IO_2_TCH_PNL1 */
+	PAD_NC(GPP_E14, NONE),
+	/* GPP_E15:     THC0_SPI1_IO_3_TCH_PNL1 */
+	PAD_NC(GPP_E15, NONE),
+	/* GPP_E16:     THC0_SPI1_RST_N_TCH_PNL1 */
+	PAD_CFG_GPO(GPP_E16, 1, DEEP),
+	/* GPP_E17:     THC0_SPI1_CS0_N_TCH_PNL1 */
+	PAD_NC(GPP_E17, NONE),
+	/* GPP_E18:     THC0_SPI1_INT_N_TCH_PNL1 */
+	PAD_CFG_GPI_APIC(GPP_E18, NONE, PLTRST, LEVEL, NONE),
+	/* GPP_VGPIO3_THC0: THC0_WOT */
+	PAD_NC(GPP_VGPIO3_THC0, NONE),
+};
+
 static const struct pad_config touchscreen_thc_i2c_enable_pads[] = {
 	/* GPP_E11:     THC0_SPI1_CLK_TCH_PNL1 */
 	PAD_NC(GPP_E11, NONE),
@@ -572,6 +593,8 @@ void fw_config_gpio_padbased_override(struct pad_config *padbased_table)
 		GPIO_PADBASED_OVERRIDE(padbased_table, touchscreen_thc_spi_enable_pads);
 		if (config->thc_wake_on_touch[0])
 			GPIO_PADBASED_OVERRIDE(padbased_table, thc0_enable_wake);
+	} else if (fw_config_probe(FW_CONFIG(TOUCHSCREEN, TOUCHSCREEN_LPSS_I2C_ELAN_REX))) {
+		GPIO_PADBASED_OVERRIDE(padbased_table, touchscreen_lpss_i2c_enable_pads);
 	} else {
 		GPIO_PADBASED_OVERRIDE(padbased_table, touchscreen_disable_pads);
 	}
diff --git a/src/mainboard/google/ocelot/variants/ocelot/overridetree.cb b/src/mainboard/google/ocelot/variants/ocelot/overridetree.cb
index d7bd320ccd..5a36e4bf0b 100644
--- a/src/mainboard/google/ocelot/variants/ocelot/overridetree.cb
+++ b/src/mainboard/google/ocelot/variants/ocelot/overridetree.cb
@@ -21,6 +21,7 @@ fw_config
 		option TOUCHSCREEN_NONE			0
 		option TOUCHSCREEN_THC_SPI		1
 		option TOUCHSCREEN_THC_I2C		2
+		option TOUCHSCREEN_LPSS_I2C_ELAN_REX	3
 	end
 	field TOUCHPAD 9 10
 		option TOUCHPAD_NONE			0
@@ -93,7 +94,7 @@ chip soc/intel/pantherlake
 		[PchSerialIoIndexI2C1]  = PchSerialIoPci,
 		[PchSerialIoIndexI2C2]  = PchSerialIoDisabled,
 		[PchSerialIoIndexI2C3]  = PchSerialIoPci,
-		[PchSerialIoIndexI2C4]  = PchSerialIoDisabled,
+		[PchSerialIoIndexI2C4]  = PchSerialIoPci,
 		[PchSerialIoIndexI2C5]  = PchSerialIoPci,
 	}"
 
@@ -109,6 +110,7 @@ chip soc/intel/pantherlake
 	#+-------------------+---------------------------+
 	#| I2C1              | TPM(cr50)                 |
 	#| I2C3              | Audio                     |
+	#| I2C4		     | Touchscreen (LPSS)	 |
 	#| I2C5              | Touchpad                  |
 	#+-------------------+---------------------------+
 	register "common_soc_config" = "{
@@ -123,6 +125,10 @@ chip soc/intel/pantherlake
 			.speed = I2C_SPEED_FAST,
 			.early_init = 1,
 		},
+		.i2c[4] = {
+			.speed = I2C_SPEED_FAST,
+			.early_init = 1,
+		},
 		.i2c[5] = {
 			.speed = I2C_SPEED_FAST,
 		},
@@ -553,6 +559,26 @@ chip soc/intel/pantherlake
 				end
 			end
 		end #I2C3
+		device ref i2c4 on
+			chip drivers/i2c/hid
+				register "generic.hid" = ""ELAN9006""
+				register "generic.desc" = ""ELAN Touchscreen""
+				register "generic.irq" = "ACPI_IRQ_LEVEL_LOW(GPP_E18_IRQ)"
+				# NOTE: pmc_gpe0_dw2 is GPP_E in baseboard devicetree.cb.
+				register "generic.wake" = "GPE0_DW2_18"
+				register "generic.probed" = "1"
+				register "generic.reset_gpio" = "ACPI_GPIO_OUTPUT_ACTIVE_LOW(GPP_E16)"
+				register "generic.reset_delay_ms" = "20"
+				register "generic.reset_off_delay_ms" = "2"
+				register "generic.enable_gpio" = "ACPI_GPIO_OUTPUT_ACTIVE_HIGH(GPP_F08)"
+				register "generic.enable_delay_ms" = "1"
+				register "generic.has_power_resource" = "1"
+				register "hid_desc_reg_offset" = "0x01"
+				device i2c 10 on
+					probe TOUCHSCREEN TOUCHSCREEN_LPSS_I2C_ELAN_REX
+				end
+			end
+		end # I2C4
 		device ref i2c5 on
 			chip drivers/i2c/hid
 				register "generic.hid" = ""HFW68H""