linux-kernel - Re: [PATCH V4 3/6] soc: qcom: eud: Add driver support for Embedded USB Debugger(EUD)

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Date:   Fri, 28 Jan 2022 08:11:19 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Souradeep Chowdhury <quic_schowdhu@...cinc.com>
Cc:     linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        devicetree@...r.kernel.org, pure.logic@...us-software.ie,
        greg@...ah.com, robh@...nel.org, linux-kernel@...r.kernel.org,
        quic_tsoni@...cinc.com, quic_psodagud@...cinc.com,
        quic_satyap@...cinc.com, quic_pheragu@...cinc.com,
        quic_rjendra@...cinc.com, quic_sibis@...cinc.com,
        quic_saipraka@...cinc.com
Subject: Re: [PATCH V4 3/6] soc: qcom: eud: Add driver support for Embedded
 USB Debugger(EUD)

On Thu 27 Jan 04:01 PST 2022, Souradeep Chowdhury wrote:

> 
> On 1/26/2022 10:17 AM, Bjorn Andersson wrote:
> > On Fri 21 Jan 07:53 CST 2022, Souradeep Chowdhury wrote:
[..]
> > > +		return PTR_ERR(chip->base);
> > > +
> > > +	chip->mode_mgr = devm_platform_ioremap_resource(pdev, 1);
> > > +	if (IS_ERR(chip->mode_mgr))
> > > +		return PTR_ERR(chip->mode_mgr);
> > > +
> > > +	chip->irq = platform_get_irq(pdev, 0);
> > > +	ret = devm_request_threaded_irq(&pdev->dev, chip->irq, handle_eud_irq,
> > > +			handle_eud_irq_thread, IRQF_ONESHOT, NULL, chip);
> > > +	if (ret)
> > > +		return dev_err_probe(chip->dev, ret, "failed to allocate irq\n");
> > > +
> > > +	enable_irq_wake(chip->irq);
> > > +
> > > +	platform_set_drvdata(pdev, chip);
> > > +
> > > +	return 0;
> > Per the updated binding, the EUD would now be a usb-role-switch as well
> > and when not enabled should simply propagate the incoming requests. So I
> > was expecting this to register as a usb_role_switch as well...
> 
> Can you please elaborate on this?
> 
> Do I need to define a separate 'usb_role_switch_desc' here and register
> using 'usb_role_switch_register'?
> 
> Also what should be the set method in this case for usb_role_switch_desc?
> 

My expectation is that in normal operation pmic_glink will provide role
switching requests and then as you enable the EUD it will force the role
to gadget.

So my suggestion was that you make eud a role-switch and as long as EUD
is disabled you just pass through the role-switch vote from pmic_glink
onto the dwc3.

Perhaps I'm misunderstanding how this is really working.

Regards,
Bjorn