From:   Hans de Goede <hdegoede@redhat.com>
To:     "Rafael J . Wysocki" <rjw@rjwysocki.net>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Mark Gross <markgross@kernel.org>,
        Andy Shevchenko <andy@infradead.org>,
        Wolfram Sang <wsa@the-dreams.de>,
        Sebastian Reichel <sre@kernel.org>,
        MyungJoo Ham <myungjoo.ham@samsung.com>,
        Chanwoo Choi <cw00.choi@samsung.com>,
        Ard Biesheuvel <ardb@kernel.org>
Cc:     Hans de Goede <hdegoede@redhat.com>, Len Brown <lenb@kernel.org>,
        linux-acpi@vger.kernel.org, Yauhen Kharuzhy <jekhor@gmail.com>,
        Tsuchiya Yuto <kitakar@gmail.com>,
        platform-driver-x86@vger.kernel.org, linux-i2c@vger.kernel.org,
        linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-efi@vger.kernel.org
Subject: [PATCH v2 20/20] extcon: intel-cht-wc: Report RID_A for ACA adapters
Date:   Sun, 14 Nov 2021 18:03:35 +0100
Message-Id: <20211114170335.66994-21-hdegoede@redhat.com>
In-Reply-To: <20211114170335.66994-1-hdegoede@redhat.com>
References: <20211114170335.66994-1-hdegoede@redhat.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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 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.

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 1030610a3494..c92bc98cb428 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;
 	}
 }
-- 
2.31.1