The Dell Latitude 5285 2-in-1 has a BIOS bug where the ACPI GEXP device
and the I2C4 controller (INT3446) both claim the same MMIO region via the
shared SB04 variable. This causes intel_lpss_acpi to fail binding to I2C4
with -EBUSY, preventing the front camera (OV5670) sensor from being
registered.

Add a DMI quirk that selects IGNORE_RESOURCE_CONFLICTS for INT3446 on this
machine, matching the existing pattern used by other LPSS quirks.

Signed-off-by: Thierry Chatard <tchatard@gmail.com>
---
 drivers/mfd/intel-lpss-acpi.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/drivers/mfd/intel-lpss-acpi.c b/drivers/mfd/intel-lpss-acpi.c
index 63406026d..7d0964848 100644
--- a/drivers/mfd/intel-lpss-acpi.c
+++ b/drivers/mfd/intel-lpss-acpi.c
@@ -13,6 +13,8 @@
 #include <linux/ioport.h>
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
+#include <linux/acpi.h>
+#include <linux/dmi.h>
 #include <linux/pm.h>
 #include <linux/pm_runtime.h>
 #include <linux/platform_device.h>
@@ -52,6 +54,15 @@ static const struct intel_lpss_platform_info spt_i2c_info = {
 	.swnode = &spt_i2c_node,
 };
 
+/* Same as spt_i2c_info but with QUIRK_IGNORE_RESOURCE_CONFLICTS for Dell 5285
+ * where ACPI GEXP device conflicts with I2C4 (INT3446) MMIO resources.
+ */
+static const struct intel_lpss_platform_info spt_i2c_info_ignore_conflicts = {
+	.clk_rate = 120000000,
+	.swnode = &spt_i2c_node,
+	.quirks = QUIRK_IGNORE_RESOURCE_CONFLICTS,
+};
+
 static const struct property_entry uart_properties[] = {
 	PROPERTY_ENTRY_U32("reg-io-width", 4),
 	PROPERTY_ENTRY_U32("reg-shift", 2),
@@ -172,6 +183,16 @@ static const struct acpi_device_id intel_lpss_acpi_ids[] = {
 };
 MODULE_DEVICE_TABLE(acpi, intel_lpss_acpi_ids);
 
+static const struct dmi_system_id dell5285_lpss_dmi[] = {
+	{
+		.matches = {
+			DMI_EXACT_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+			DMI_EXACT_MATCH(DMI_PRODUCT_NAME, "Latitude 5285"),
+		},
+	},
+	{ }
+};
+
 static int intel_lpss_acpi_probe(struct platform_device *pdev)
 {
 	const struct intel_lpss_platform_info *data;
@@ -182,6 +203,17 @@ static int intel_lpss_acpi_probe(struct platform_device *pdev)
 	if (!data)
 		return -ENODEV;
 
+	/* Apply IGNORE_RESOURCE_CONFLICTS for I2C4 on Dell Latitude 5285.
+	 * The ACPI GEXP device conflicts with I2C4 (INT3446) MMIO resources
+	 * due to a BIOS bug where both use the same SB04 variable.
+	 */
+	if (data == &spt_i2c_info &&
+	    acpi_dev_hid_uid_match(ACPI_COMPANION(&pdev->dev), "INT3446", NULL) &&
+	    dmi_check_system(dell5285_lpss_dmi)) {
+		dev_info(&pdev->dev, "Dell 5285: applying IGNORE_RESOURCE_CONFLICTS for I2C4\n");
+		data = &spt_i2c_info_ignore_conflicts;
+	}
+
 	info = devm_kmemdup(&pdev->dev, data, sizeof(*info), GFP_KERNEL);
 	if (!info)
 		return -ENOMEM;
-- 
2.51.0