[PATCH 9/9] media: atomisp_gmin_platform: Add DMI quirk to not turn AXP ELDO2 regulator off on some boards

[Hans de Goede <hdegoede@redhat.com>]

The TrekStor SurfTab duo W1 10.1 has a hw bug where turning eldo2 back on
after having turned it off causes the CPLM3218 ambient-light-sensor on
the front camera sensor's I2C bus to crash, hanging the bus.

Add a DMI quirk table for systems on which to leave eldo2 on.

Note an alternative fix is to turn off the CPLM3218 ambient-light-sensor
as long as the camera sensor is being used, this is what Windows seems
to do as a workaround (based on analyzing the DSDT). But that is not
easy to do cleanly under Linux.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 .../media/atomisp/pci/atomisp_gmin_platform.c  | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c b/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c
index 544e3e7b3aaf..7e47db82de07 100644
--- a/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c
+++ b/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c
@@ -761,6 +761,21 @@ static int axp_regulator_set(struct device *dev, struct gmin_subdev *gs,
 	return 0;
 }
 
+/*
+ * Some boards contain a hw-bug where turning eldo2 back on after having turned
+ * it off causes the CPLM3218 ambient-light-sensor on the image-sensor's I2C bus
+ * to crash, hanging the bus. Do not turn eldo2 off on these systems.
+ */
+static const struct dmi_system_id axp_leave_eldo2_on_ids[] = {
+	{
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "TrekStor"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "SurfTab duo W1 10.1 (VT4)"),
+		},
+	},
+	{ }
+};
+
 static int axp_v1p8_on(struct device *dev, struct gmin_subdev *gs)
 {
 	int ret;
@@ -790,6 +805,9 @@ static int axp_v1p8_off(struct device *dev, struct gmin_subdev *gs)
 	if (ret)
 		return ret;
 
+	if (dmi_check_system(axp_leave_eldo2_on_ids))
+		return 0;
+
 	ret = axp_regulator_set(dev, gs, gs->eldo2_sel_reg, gs->eldo2_1p8v,
 				ELDO_CTRL_REG, gs->eldo2_ctrl_shift, false);
 	return ret;
-- 
2.33.1