linux-kernel - Re: [PATCH v4 5/9] usb: dwc3: core: make dual-role work with OTG irq

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Date:	Fri, 4 Sep 2015 12:13:28 +0300
From:	Roger Quadros <rogerq@...com>
To:	<balbi@...com>
CC:	<tony@...mide.com>, <Joao.Pinto@...opsys.com>,
	<sergei.shtylyov@...entembedded.com>, <peter.chen@...escale.com>,
	<jun.li@...escale.com>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>
Subject: Re: [PATCH v4 5/9] usb: dwc3: core: make dual-role work with OTG irq

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On 03/09/15 18:51, Felipe Balbi wrote:
> Hi,
> 
> On Thu, Sep 03, 2015 at 04:52:02PM +0300, Roger Quadros wrote:
>>>>  	if (on) {
>>>> -		dwc3_set_mode(dwc, DWC3_GCTL_PRTCAP_HOST);
>>>> +		/* OCTL.PeriMode = 0 */
>>>> +		reg = dwc3_readl(dwc->regs, DWC3_OCTL);
>>>> +		reg &= ~DWC3_OCTL_PERIMODE;
>>>> +		dwc3_writel(dwc->regs, DWC3_OCTL, reg);
>>>> +		/* unconditionally turn on VBUS */
>>>> +		reg |= DWC3_OCTL_PRTPWRCTL;
>>>> +		dwc3_writel(dwc->regs, DWC3_OCTL, reg);
>>>>  		/* start the HCD */
>>>>  		usb_otg_start_host(fsm, true);
>>>>  	} else {
>>>>  		/* stop the HCD */
>>>>  		usb_otg_start_host(fsm, false);
>>>> +		/* turn off VBUS */
>>>> +		reg = dwc3_readl(dwc->regs, DWC3_OCTL);
>>>> +		reg &= ~DWC3_OCTL_PRTPWRCTL;
>>>> +		dwc3_writel(dwc->regs, DWC3_OCTL, reg);
>>>> +		/* OCTL.PeriMode = 1 */
>>>> +		reg = dwc3_readl(dwc->regs, DWC3_OCTL);
>>>> +		reg |= DWC3_OCTL_PERIMODE;
>>>> +		dwc3_writel(dwc->regs, DWC3_OCTL, reg);
>>>>  	}
>>>
>>> it looks like you're not really following the fluxchart from SNPS
>>> documentation, see Figure 11-4 on section 11.1.4.5
>>
>> Did you mean that I'm ignoring all OTG bits (HNP/SRP/ADP)?
> 
> yes and no :-)  There's a rather complex flux chart which details how we
> switch from host to peripheral and vice versa. We need to follow that to
> the smallest details since that's what IP provider considers to be
> correct. If we deviate from that we should have very strong reasons for
> doing so and we also want big, fat, long comments in source code
> detailing why and how we're deviating :-)
> 
Understood. I'll update this accordingly.

- --
cheers,
- -roger
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