linux-kernel - Re: [RFC][PATCH v2 08/13] usb: otg: hub: Notify OTG fsm when A device sets b_hnp

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Date:	Fri, 17 Apr 2015 10:32:35 +0300
From:	Roger Quadros <rogerq@...com>
To:	Peter Chen <peter.chen@...escale.com>
CC:	<gregkh@...uxfoundation.org>, <balbi@...com>,
	<stern@...land.harvard.edu>, <dan.j.williams@...el.com>,
	<jun.li@...escale.com>, <mathias.nyman@...ux.intel.com>,
	<tony@...mide.com>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>
Subject: Re: [RFC][PATCH v2 08/13] usb: otg: hub: Notify OTG fsm when A device
 sets b_hnp_enable

On 17/04/15 05:28, Peter Chen wrote:
> On Tue, Apr 14, 2015 at 01:41:55PM +0300, Roger Quadros wrote:
>> This is the a_set_b_hnp_enable flag in the OTG state machine
>> diagram and must be set when the A-Host has successfully set
>> the b_hnp_enable feature of the OTG-B-Peripheral attached to it.
>>
>> When this bit changes we kick our OTG FSM to make note of the
>> change and act accordingly.
>>
>> Signed-off-by: Roger Quadros <rogerq@...com>
>> ---
>>  drivers/usb/core/hub.c | 11 ++++++++++-
>>  1 file changed, 10 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
>> index d7c3d5a..ab0d498 100644
>> --- a/drivers/usb/core/hub.c
>> +++ b/drivers/usb/core/hub.c
>> @@ -22,6 +22,7 @@
>>  #include <linux/usb/hcd.h>
>>  #include <linux/usb/otg.h>
>>  #include <linux/usb/quirks.h>
>> +#include <linux/usb/usb-otg.h>
>>  #include <linux/workqueue.h>
>>  #include <linux/mutex.h>
>>  #include <linux/random.h>
>> @@ -2270,6 +2271,9 @@ static int usb_enumerate_device_otg(struct usb_device *udev)
>>  						"can't set HNP mode: %d\n",
>>  						err);
>>  					bus->b_hnp_enable = 0;
>> +				} else {
>> +					/* notify OTG fsm about a_set_b_hnp_enable */
>> +					usb_otg_kick_fsm(udev->bus->controller);
>>  				}
>>  			}
>>  		}
>> @@ -4244,8 +4248,13 @@ hub_port_init (struct usb_hub *hub, struct usb_device *udev, int port1,
>>  	 */
>>  	if (!hdev->parent) {
>>  		delay = HUB_ROOT_RESET_TIME;
>> -		if (port1 == hdev->bus->otg_port)
>> +		if (port1 == hdev->bus->otg_port) {
>>  			hdev->bus->b_hnp_enable = 0;
>> +#ifdef CONFIG_USB_OTG
>> +			/* notify OTG fsm about a_set_b_hnp_enable change */
>> +			usb_otg_kick_fsm(hdev->bus->controller);
>> +#endif
>> +		}
>>  	}
>>  
>>  	/* Some low speed devices have problems with the quick delay, so */
>> -- 
>> 2.1.0
>>
> 
> Since the fsm has already kicked, the only thing we need is update
> fsm.a_set_b_hnp_enable, but this flag is missing at current fsm
> structure.

Every time the input changes, the fsm has to be re-kicked.

Instead of fsm.a_set_b_hnp_enable we use fsm->otg->host->b_hnp_enable
in the fsm.
USB host stack doesn't have access to fsm structure but the OTG state
machine has access to hcd.

cheers,
-roger

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