[PATCH v4 20/20] extcon: intel-cht-wc: Report RID_A for ACA adapters

Hans de Goede
2022-01-30T20:48:24Z

Make cht_wc_extcon_get_id() report RID_A for ACA adapters, instead of
reporting ID_FLOAT.

According to the spec. we should read the USB-ID pin ADC value
to determine the resistance of the used pull-down resister and
then return RID_A / RID_B / RID_C based on this. But all "Accessory
Charger Adapter"s (ACAs) which users can actually buy always use
a combination of a charging port with one or more USB-A ports, so
they should always use a resistor indicating RID_A. But the spec
is hard to read / badly-worded so some of them actually indicate
they are a RID_B ACA even though they clearly are a RID_A ACA.

To workaround this simply always return INTEL_USB_RID_A, which
matches all the ACAs which users can actually buy.

Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
drivers/extcon/extcon-intel-cht-wc.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/extcon/extcon-intel-cht-wc.c b/drivers/extcon/extcon-intel-cht-wc.c
index 144cb5d8cd47..2a8d41cbf41c 100644
--- a/drivers/extcon/extcon-intel-cht-wc.c
+++ b/drivers/extcon/extcon-intel-cht-wc.c
@@ -121,13 +121,21 @@ static int cht_wc_extcon_get_id(struct cht_wc_extcon_data *ext, int pwrsrc_sts)
return INTEL_USB_ID_GND;
case CHT_WC_PWRSRC_RID_FLOAT:
return INTEL_USB_ID_FLOAT;
+ /*
+ * According to the spec. we should read the USB-ID pin ADC value here
+ * to determine the resistance of the used pull-down resister and then
+ * return RID_A / RID_B / RID_C based on this. But all "Accessory
+ * Charger Adapter"s (ACAs) which users can actually buy always use
+ * a combination of a charging port with one or more USB-A ports, so
+ * they should always use a resistor indicating RID_A. But the spec
+ * is hard to read / badly-worded so some of them actually indicate
+ * they are a RID_B ACA evnen though they clearly are a RID_A ACA.
+ * To workaround this simply always return INTEL_USB_RID_A, which
+ * matches all the ACAs which users can actually buy.
+ */
case CHT_WC_PWRSRC_RID_ACA:
+ return INTEL_USB_RID_A;
default:
- /*
- * Once we have IIO support for the GPADC we should read
- * the USBID GPADC channel here and determine ACA role
- * based on that.
- */
return INTEL_USB_ID_FLOAT;
}
}
--
2.33.1