linux-kernel - Re: [PATCH v7 07/10] usb: dbc: handle endpoint stall

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Date:	Wed, 02 Mar 2016 14:58:40 +0200
From:	Mathias Nyman <mathias.nyman@...ux.intel.com>
To:	Lu Baolu <baolu.lu@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 07/10] usb: dbc: handle endpoint stall

On 26.01.2016 14:58, Lu Baolu wrote:
> In case of endpoint stall, software is able to detect the situation
> by reading DCCTRL.HIT or DCCTRL.HOT bits. DbC follows the normal USB
> framework to handle endpoint stall. When software detects endpoint
> stall situation, it should wait until endpoint is recovered before
> read or write oprations.
>
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> ---
>   drivers/usb/early/xhci-dbc.c | 36 ++++++++++++++++++++++++++++++++++++
>   1 file changed, 36 insertions(+)
>
> diff --git a/drivers/usb/early/xhci-dbc.c b/drivers/usb/early/xhci-dbc.c
> index c81df40..344d93e 100644
> --- a/drivers/usb/early/xhci-dbc.c
> +++ b/drivers/usb/early/xhci-dbc.c
> @@ -1163,6 +1163,37 @@ static int xdbc_wait_until_dbc_configured(void)
>   	return -ETIMEDOUT;
>   }
>
> +static int xdbc_wait_until_epstall_cleared(bool read)
> +{
> +	int timeout = 0;
> +
> +	if (read) {
> +		do {
> +			if (!(readl(&xdbcp->xdbc_reg->control) & CTRL_HIT)) {
> +				xdbcp->in_ep_state = EP_RUNNING;
> +
> +				return 0;
> +			}
> +
> +			xdbcp->in_ep_state = EP_HALTED;
> +			xdbc_udelay(10);
> +		} while (timeout++ < XDBC_LOOPS);
> +	} else {
> +		do {
> +			if (!(readl(&xdbcp->xdbc_reg->control) & CTRL_HOT)) {
> +				xdbcp->out_ep_state = EP_RUNNING;
> +
> +				return 0;
> +			}
> +
> +			xdbcp->out_ep_state = EP_HALTED;
> +			xdbc_udelay(10);
> +		} while (timeout++ < XDBC_LOOPS);
> +	}
> +
> +	return -ETIMEDOUT;
> +}
>

how about something like:

enum xdbc_ep_state *ep_state;
u32 halt_bit;

if (read) {
	ep_state = &xdbcp->in_ep_state
	halt_bit = CTRL_HIT
} else {
  	ep_state = &xdbcp->out_ep_state
	halt_bit = CTRL_HOT
}
do {
	if (!(readl(..) & halt_bit)) {
		*ep_state = EP_RUNNING;
		return 0;
	}
	*ep_state = EP_HALTED;
	delay()
} while (..)


+
>   static int xdbc_bulk_transfer(void *data, int size, int loops, bool read)
>   {
>   	u64 addr;
> @@ -1182,6 +1213,11 @@ static int xdbc_bulk_transfer(void *data, int size, int loops, bool read)
>   		return -EPERM;
>   	}
>
> +	if (xdbc_wait_until_epstall_cleared(read)) {
> +		xdbc_trace("%s: endpoint not ready\n", __func__);
> +		return -EPERM;

Is -EPERM appropriate here?
Not sure about what error codes the device side is using, but usually HALT is set due to some
Data buffer/transmission/TRB error.
In this case the failure is that debug host failed to send a clearFeature(EP_HALT) request in time.

-Mathias