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

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Date:	Thu, 3 Mar 2016 14:00:58 +0800
From:	Lu Baolu <baolu.lu@...ux.intel.com>
To:	Mathias Nyman <mathias.nyman@...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 03/02/2016 08:58 PM, Mathias Nyman wrote:
> 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 (..)

Sure. I will refine this part of code.

>
>
> +
>>   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.

Yes. This is done by debug host firmware. OS needs to check and wait.

This return value is used to tell the up layer what happened. -EPERM is definitely not appropriate here.
I will use EIO as suggested by Felipe.

>
> -Mathias
>

Thanks,
-Baolu