linux-kernel - extcon: sm5502: USB-HOST (OTG) detection not working

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Message-ID: <20191011145015.GA127238@gerhold.net>
Date:   Fri, 11 Oct 2019 16:50:15 +0200
From:   Stephan Gerhold <stephan@...hold.net>
To:     Chanwoo Choi <cw00.choi@...sung.com>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        linux-kernel@...r.kernel.org
Subject: extcon: sm5502: USB-HOST (OTG) detection not working

Hi Chanwoo,

after getting interrupts working on my Samsung Galaxy A5 (2015),
I am now trying to make the extcon device detect USB-HOST=1
when I plug in an USB OTG adapter.

At the moment, the driver can sucessfully detect:
  - USB=1 + SDP=1 when I detect the phone to a PC
  - DCP=1 when I connect it to an AC charger
but it does not set USB-HOST=1 when I connect the USB OTG adapter.

It seems to be a problem in the sm5502 driver, since I do get an
SM5502_IRQ_INT1_ATTACH interrupt when I plug in the USB OTG adapter.

In this case, SM5502 reports:
    SM5502_REG_ADC = 0x00 (SM5502_MUIC_ADC_GROUND)
    SM5502_REG_DEV_TYPE1 = 0x80 (SM5502_REG_DEV_TYPE1_USB_OTG_MASK)

However, at the moment the sm5502 driver ignores all attach events with
SM5502_REG_ADC == SM5502_MUIC_ADC_GROUND:

	/*
	 * If ADC is SM5502_MUIC_ADC_GROUND(0x0), external cable hasn't
	 * connected with to MUIC device.
	 */
	cable_type = adc & SM5502_REG_ADC_MASK;
	if (cable_type == SM5502_MUIC_ADC_GROUND)
		return SM5502_MUIC_ADC_GROUND;

However, I definitely have a cable attached in this case...

The sm5502 driver seems to expect SM5502_REG_ADC == SM5502_MUIC_ADC_OPEN.
Any idea why my hardware reports ADC_GROUND for the USB OTG adapter
instead of ADC_OPEN?

Confusingly, the driver used in the original downstream kernel of
the Samsung Galaxy A5 [1] calls ADC = 0x00 "ADC_OTG" instead of
"ADC_GROUND".
So getting ADC = 0x00 may not be entirely unexpected here...

Thanks in advance,
Stephan

[1]: https://github.com/msm8916-mainline/android_kernel_qcom_msm8916/blob/SM-A500FU/drivers/misc/sm5502.c#L195