linux-kernel - Re: [PATCH] usb: musb: dsps: handle the otg_state_a_wait_vrise

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Date:	Fri, 21 Aug 2015 14:29:37 +0200
From:	Gregory CLEMENT <gregory.clement@...e-electrons.com>
To:	Felipe Balbi <balbi@...com>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, stable@...r.kernel.org
Subject: Re: [PATCH] usb: musb: dsps: handle the otg_state_a_wait_vrise_timeout
 case

Hi all,

On 20/08/2015 18:12, Gregory CLEMENT wrote:
> According to the OTG specification after a timeout of
> OTG_TIME_A_WAIT_VRISE (the maximum value is 100ms) the driver must
> move from the state a_wait_vrise to the state a_wait_bcon. However,
> the dsps version of musb does not handle this case.
> 
> Without it, the driver could remain stuck in the a_wait_vrise. It can
> be reproduce with the following steps:
> 
> 1) Boot a board with no USB adapter inserted
> 2) Insert an empty OTG adapter
> 3) Wait 2 seconds then remove the OTG adapter
> 4) The unit is now stuck in host mode, the VBUS switch is latched on
> and the ID pin is no longer polled.
> 
> The only way to exit this state was to insert a OTG adapter with an
> USB device connected. Until this, the usb device mode was not
> available.
> 
> It was tested on a AM35x based board.
> 
> CC: <stable@...r.kernel.org>
> Signed-off-by: Gregory CLEMENT <gregory.clement@...e-electrons.com>
> ---
>  drivers/usb/musb/musb_dsps.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/musb/musb_dsps.c b/drivers/usb/musb/musb_dsps.c
> index 65d931a..2d22683 100644
> --- a/drivers/usb/musb/musb_dsps.c
> +++ b/drivers/usb/musb/musb_dsps.c
> @@ -145,6 +145,7 @@ struct dsps_glue {
>  	struct timer_list timer;	/* otg_workaround timer */
>  	unsigned long last_timer;    /* last timer data for each instance */
>  	bool sw_babble_enabled;
> +	int otg_state_a_wait_vrise_timeout;
>  
>  	struct dsps_context context;
>  	struct debugfs_regset32 regset;
> @@ -268,9 +269,18 @@ static void otg_timer(unsigned long _musb)
>  
>  	spin_lock_irqsave(&musb->lock, flags);
>  	switch (musb->xceiv->otg->state) {
> +	case OTG_STATE_A_WAIT_VRISE:
> +		if ((glue->otg_state_a_wait_vrise_timeout)) {
> +				musb->xceiv->otg->state = OTG_STATE_A_WAIT_BCON;
> +				musb->is_active = 0;
> +			}
> +		mod_timer(&glue->timer, jiffies +
> +			  msecs_to_jiffies(OTG_TIME_A_WAIT_VRISE));

After more test on more USB drive, it seems that for some of them
OTG_TIME_A_WAIT_VRISE is too short. 200ms seems better. It is
disturbing because according to the OTG specification the maximum
is 100ms, however I am not so surprised that USB device maker don't
follow it.


> +		break;
>  	case OTG_STATE_A_WAIT_BCON:
>  		dsps_writeb(musb->mregs, MUSB_DEVCTL, 0);
>  		skip_session = 1;
> +		glue->otg_state_a_wait_vrise_timeout = 0;
>  		/* fall */
>  
>  	case OTG_STATE_A_IDLE:
> @@ -359,7 +369,9 @@ static irqreturn_t dsps_interrupt(int irq, void *hci)
>  			MUSB_HST_MODE(musb);
>  			musb->xceiv->otg->default_a = 1;
>  			musb->xceiv->otg->state = OTG_STATE_A_WAIT_VRISE;
> -			del_timer(&glue->timer);
> +			glue->otg_state_a_wait_vrise_timeout = 1;
> +			mod_timer(&glue->timer, jiffies +
> +				  msecs_to_jiffies(OTG_TIME_A_WAIT_VRISE));
>  		} else {
>  			musb->is_active = 0;
>  			MUSB_DEV_MODE(musb);
> 


-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com
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