linux-kernel - [PATCH v2 2/2] extcon: max77843: support USB accessories as external USB hosts

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Message-Id: <20170402053542.29570-3-andi@etezian.org>
Date:   Sun,  2 Apr 2017 14:35:42 +0900
From:   Andi Shyti <andi.shyti@...il.com>
To:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Jaewon Kim <jaewon02.kim@...sung.com>
Cc:     Seung-Woo Kim <sw0312.kim@...sung.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linux-kernel@...r.kernel.org, Andi Shyti <andi.shyti@...sung.com>,
        Andi Shyti <andi@...zian.org>
Subject: [PATCH v2 2/2] extcon: max77843: support USB accessories as external USB hosts

From: Andi Shyti <andi.shyti@...sung.com>

The ADC state defines the resistance that a USB device has in
order to distinguish between devices.

The external accessories (like the Gear VR) are defined as:

MAX77843_MUIC_ADC_RESERVED_ACC_1
MAX77843_MUIC_ADC_RESERVED_ACC_2
MAX77843_MUIC_ADC_RESERVED_ACC_3
MAX77843_MUIC_ADC_RESERVED_ACC_4
MAX77843_MUIC_ADC_RESERVED_ACC_5

and they should be set as such in the extcon driver.

Do not ignore interrupts generated by external accessories by
handling cables of the type from any of the above.

Do not handle any charging related action. This can be
misleading as also external devices might have some power and in
such cases the MUIC might consider them as power providers. In
this case check the value of the adc and if it corresponds to
one or the MAX77843_MUIC_ADC_RESERVED_ACC_*, return a no-action
value (MAX77843_MUIC_CHG_NONE).

Signed-off-by: Andi Shyti <andi.shyti@...sung.com>
---
 drivers/extcon/extcon-max77843.c | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/drivers/extcon/extcon-max77843.c b/drivers/extcon/extcon-max77843.c
index fcdabc4b4025..154d65afd45a 100644
--- a/drivers/extcon/extcon-max77843.c
+++ b/drivers/extcon/extcon-max77843.c
@@ -271,6 +271,20 @@ static int max77843_muic_get_cable_type(struct max77843_muic_info *info,
 		} else {
 			*attached = true;
 			switch (adc) {
+			/*
+			 * the MAX77843_MUIC_ADC_RESERVED_ACC_* type are
+			 * external eccessories and as such they don't
+			 * need any charging action. In this case just
+			 * return MAX77843_MUIC_CHG_NONE so that charging type
+			 * interrupts are ignored.
+			 */
+			case MAX77843_MUIC_ADC_RESERVED_ACC_1:
+			case MAX77843_MUIC_ADC_RESERVED_ACC_2:
+			case MAX77843_MUIC_ADC_RESERVED_ACC_3:
+			case MAX77843_MUIC_ADC_RESERVED_ACC_4:
+			case MAX77843_MUIC_ADC_RESERVED_ACC_5:
+				info->prev_chg_type = MAX77843_MUIC_CHG_NONE;
+				break;
 			case MAX77843_MUIC_ADC_GROUND:
 				info->prev_chg_type = MAX77843_MUIC_CHG_GND;
 				break;
@@ -403,6 +417,11 @@ static int max77843_muic_adc_handler(struct max77843_muic_info *info)
 
 	switch (cable_type) {
 	case MAX77843_MUIC_ADC_GROUND:
+	case MAX77843_MUIC_ADC_RESERVED_ACC_1:
+	case MAX77843_MUIC_ADC_RESERVED_ACC_2:
+	case MAX77843_MUIC_ADC_RESERVED_ACC_3:
+	case MAX77843_MUIC_ADC_RESERVED_ACC_4:
+	case MAX77843_MUIC_ADC_RESERVED_ACC_5:
 		ret = max77843_muic_adc_gnd_handler(info);
 		if (ret < 0)
 			return ret;
@@ -427,11 +446,6 @@ static int max77843_muic_adc_handler(struct max77843_muic_info *info)
 	case MAX77843_MUIC_ADC_REMOTE_S10_BUTTON:
 	case MAX77843_MUIC_ADC_REMOTE_S11_BUTTON:
 	case MAX77843_MUIC_ADC_REMOTE_S12_BUTTON:
-	case MAX77843_MUIC_ADC_RESERVED_ACC_1:
-	case MAX77843_MUIC_ADC_RESERVED_ACC_2:
-	case MAX77843_MUIC_ADC_RESERVED_ACC_3:
-	case MAX77843_MUIC_ADC_RESERVED_ACC_4:
-	case MAX77843_MUIC_ADC_RESERVED_ACC_5:
 	case MAX77843_MUIC_ADC_AUDIO_DEVICE_TYPE2:
 	case MAX77843_MUIC_ADC_PHONE_POWERED_DEV:
 	case MAX77843_MUIC_ADC_TTY_CONVERTER:
-- 
2.11.0