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

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Message-ID: <20200214130755.GA93507@gerhold.net>
Date:   Fri, 14 Feb 2020 14:07:55 +0100
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: Re: extcon: sm5502: USB-HOST (OTG) detection not working

Hi Chanwoo,

On Fri, Oct 11, 2019 at 04:50:21PM +0200, Stephan Gerhold wrote:
> 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

This mail is quite old now but I am still confused by this.
Any idea what could be wrong here?

I was not able to find any datasheet for SM5502 unfortunately...

Thanks,
Stephan