Hi,
Bin Liu <b-liu@xxxxxx> writes:
> Hi,
>
> On 11/06/2015 11:11 AM, Felipe Balbi wrote:
>>
>> Hi,
>>
>> Bin Liu <b-liu@xxxxxx> writes:
>>> Here are a few changes in musb_h_tx_flush_fifo().
>>>
>>> - It has been observed that sometimes (if not always) musb is unable
>>> to flush tx fifo during urb dequeue when disconnect a device. But
>>> it seems to be harmless, since the tx fifo flush is done again in
>>> musb_ep_program() when re-use the hw_ep.
>>>
>>> But the WARN() floods the console in the case when multiple tx urbs
>>> are queued, so change it to dev_WARN_ONCE().
>>>
>>> - applications could queue up many tx urbs, then the 1ms delay could
>>> causes minutes of delay in device disconnect. So remove it to get
>>> better user experience. The 1ms delay does not help the flushing
>>> anyway.
>>>
>>> - cleanup the debug code - related to lastcsr.
>>>
>>> Signed-off-by: Bin Liu <b-liu@xxxxxx>
>>> ---
>>> drivers/usb/musb/musb_host.c | 12 ++++++------
>>> 1 file changed, 6 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c
>>> index 883a9ad..1c7f858 100644
>>> --- a/drivers/usb/musb/musb_host.c
>>> +++ b/drivers/usb/musb/musb_host.c
>>> @@ -112,22 +112,22 @@ static void musb_h_tx_flush_fifo(struct musb_hw_ep *ep)
>>> struct musb *musb = ep->musb;
>>> void __iomem *epio = ep->regs;
>>> u16 csr;
>>> - u16 lastcsr = 0;
>>> int retries = 1000;
>>>
>>> csr = musb_readw(epio, MUSB_TXCSR);
>>> while (csr & MUSB_TXCSR_FIFONOTEMPTY) {
>>
>> are you not going to check that TXPKTRDY is still set ? I guess that
>> could be another WARN(), actually, since it should never happen. But
>> maybe it's subject to a separate patch:
>
> Since the check does not help the flush issue, I would prefer leave it
> for the future patch which does the proper fix.
>
>>
>> dev_WARN_ONCE(dev, !(csr & MUSB_TXCSR_TXPKTRDY),
>> "TxPktRdy should still be set!);
>
> I am not sure the WARN() here is right, it is not a error condition when
> FIFONOTEMPTY is set but TXPKTRDY is not.
if TXPKTRDY has been cleared by MUSB, it means the packet has been
transferred and, thus, there's nothing to left to flush. So it is a race
indeed and I'd like to know if it ever happens.
>>> - if (csr != lastcsr)
>>> - dev_dbg(musb->controller, "Host TX FIFONOTEMPTY csr: %02x\n", csr);
>>> - lastcsr = csr;
>>> csr |= MUSB_TXCSR_FLUSHFIFO | MUSB_TXCSR_TXPKTRDY;
>>> musb_writew(epio, MUSB_TXCSR, csr);
>>> csr = musb_readw(epio, MUSB_TXCSR);
>>> - if (WARN(retries-- < 1,
>>> +
>>> + /*
>>> + * FIXME: sometimes the tx fifo flush failed, it has been
>>> + * seeing during device disconnect.
>> seen ?
>>
>> also, you probably want to describe here how you reproduced
>> this. Something along the lines of:
>>
>> Reproduced at least with AM335x Evaluation Module when an input
>> device (using $device - VID:PID - here) is attached to its host
>> port.
>>
>> That way, it's clear that the thing has really been reproduced and it
>> gives people instructions on how to reproduce.
>>
> Better put this explanation in the commit message area, not here
> in-line?
I'd say both. When I'm looking at the code, it's not always that I go
look at the commit log to figure out what happened for the function to
get to this state; sometimes I do, but not always.
--
balbi
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