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

[Felipe Balbi]

Hi,

Mathias Nyman <mathias.ny...@linux.intel.com> writes:
> [ text/plain ]
> 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...@linux.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 (..)

I'll agree, this looks better. Might also want to refactor the handshake
loop to its own function:

static int xdbg_ep_state_handshake(enum xdbc_ep_state *ep_state, u32 halt_bit)
{
        do {
                if (!(readl(...) & halt_bit)) {
                        ...
                }
                *ep_state = EP_HALTED;
                delay(...);
        } while (...)

>> @@ -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.

EIO perhaps ?

> In this case the failure is that debug host failed to send a
> clearFeature(EP_HALT) request in time.

I haven't read the spec, but does it define a maximum time for this to
happen ?

-- 
balbi

signature.asc
Description: PGP signature