linux-kernel - Re: [PATCH v4 13/13] usb: otg: Add dual-role device (DRD) support

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Date:	Mon, 7 Sep 2015 15:53:48 +0800
From:	Li Jun <b47624@...escale.com>
To:	Roger Quadros <rogerq@...com>
CC:	<stern@...land.harvard.edu>, <balbi@...com>,
	<gregkh@...uxfoundation.org>, <peter.chen@...escale.com>,
	<dan.j.williams@...el.com>, <jun.li@...escale.com>,
	<mathias.nyman@...ux.intel.com>, <tony@...mide.com>,
	<Joao.Pinto@...opsys.com>, <abrestic@...omium.org>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-omap@...r.kernel.org>
Subject: Re: [PATCH v4 13/13] usb: otg: Add dual-role device (DRD) support

On Mon, Aug 24, 2015 at 04:21:24PM +0300, Roger Quadros wrote:
> DRD mode is a reduced functionality OTG mode. In this mode
> we don't support SRP, HNP and dynamic role-swap.
> 
> In DRD operation, the controller mode (Host or Peripheral)
> is decided based on the ID pin status. Once a cable plug (Type-A
> or Type-B) is attached the controller selects the state
> and doesn't change till the cable in unplugged and a different
> cable type is inserted.
> 
> As we don't need most of the complex OTG states and OTG timers
> we implement a lean DRD state machine in usb-otg.c.
> The DRD state machine is only interested in 2 hardware inputs
> 'id' and 'b_sess_vld'.
> 
> Signed-off-by: Roger Quadros <rogerq@...com>
> ---
>  drivers/usb/common/usb-otg.c | 178 +++++++++++++++++++++++++++++++++++++++++--
>  include/linux/usb/otg-fsm.h  |   5 ++
>  include/linux/usb/otg.h      |   2 +
>  3 files changed, 177 insertions(+), 8 deletions(-)
> 

... ...

> +/* Called when entering a DRD state */
> +static void drd_set_state(struct otg_fsm *fsm, enum usb_otg_state new_state)
> +{
> +	struct usb_otg *otgd = container_of(fsm, struct usb_otg, fsm);
> +
> +	if (fsm->otg->state == new_state)
> +		return;
> +
> +	fsm->state_changed = 1;
> +	dev_dbg(otgd->dev, "otg: set state: %s\n",
> +		usb_otg_state_string(new_state));
> +	switch (new_state) {
> +	case OTG_STATE_B_IDLE:
> +		drd_set_protocol(fsm, PROTO_UNDEF);

You didn't address this comment for your previous version.

otg_drv_vbus(fsm, 0);

> +		break;
> +	case OTG_STATE_B_PERIPHERAL:
> +		drd_set_protocol(fsm, PROTO_GADGET);

otg_drv_vbus(fsm, 0);

> +		break;
> +	case OTG_STATE_A_HOST:

otg_drv_vbus(fsm, 1);

> +		drd_set_protocol(fsm, PROTO_HOST);
> +		break;
> +	case OTG_STATE_UNDEFINED:
> +	case OTG_STATE_B_SRP_INIT:
> +	case OTG_STATE_B_WAIT_ACON:
> +	case OTG_STATE_B_HOST:
> +	case OTG_STATE_A_IDLE:
> +	case OTG_STATE_A_WAIT_VRISE:
> +	case OTG_STATE_A_WAIT_BCON:
> +	case OTG_STATE_A_SUSPEND:
> +	case OTG_STATE_A_PERIPHERAL:
> +	case OTG_STATE_A_WAIT_VFALL:
> +	case OTG_STATE_A_VBUS_ERR:
> +	default:
> +		dev_warn(otgd->dev, "%s: otg: invalid state: %s\n",
> +			 __func__, usb_otg_state_string(new_state));
> +		break;
> +	}
> +
> +	fsm->otg->state = new_state;
> +}
> +
... ...
--
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