[PATCH RESEND] ath10k: Fix potential Rx ring corruption

[Ben Greear]

On 01/11/2015 02:06 AM, Vasanthakumar Thiagarajan wrote:
>
>
>
>> Well, problem is not solved after all.  Had total of 5 crashes on overnight run, must have
>> all been before midnight, because that is the earliest logs I see (journald was not configured
>> to use enough space...fixed for next time) and no crashes since then.
>
> Not sure about the crash you are originally seeing. This commit fixes rx ring buffer corruption,
> this could make some difference in buffer corruption in copy engine 1.

Well, it wasn't a crash until I added keep-alive timer and assert, what I mean is that
the WMI transport hangs, apparently due to lost message (or ack) or two between firmware
and host.

Slow to debug, because the second-to-last dbglog message from firmware is sent towards host
but never seen by host.  So I am going to have to play some more tricks to see the missing dbglog messages.

Thanks,
Ben


>> Still, it is at least no worse.
>>
>> I wonder if similar wb() is needed in the firmware somewhere?
>
> Unlikely, there will be enough time for host to see the updated index and
> rx buffer after fw updates them while sending htt rx indication. Host accesses
> them only when processing the htt message.


>
> Vasanth
>
>>
>> Thanks,
>> Ben
>>
>> On 01/09/2015 04:36 PM, Ben Greear wrote:
>>> I added this to my tree (and a bunch more debug stuff to track
>>> CE transport-ids), and I've done about 4500 station reconnects over
>>> the last 2 hours and no tx-credits hang issue so far.
>>>
>>> Could be my debugging code or that I'm getting lucky, but I'm hopeful
>>> that your patch actually fixed the problem I was seeing!
>>>
>>> Thanks,
>>> Ben
>>>
>>>
>>> On 01/09/2015 09:19 AM, Vasanthakumar Thiagarajan wrote:
>>>> When replenishing Rx buffers driver updates the address of the
>>>> buffer and the index of rx buffer in rx ring to the firmware.
>>>> Change in order by CPU can cause rx ring corruption. Add memory
>>>> barrier before updating rx buffer index to guarantee the order.
>>>>
>>>> This could fix some instances of rx ring corruption due to done
>>>> bit in rx attention flag not set.
>>>>
>>>> Signed-off-by: Vasanthakumar Thiagarajan <vthiagar at qti.qualcomm.com>
>>>> ---
>>>>    drivers/net/wireless/ath/ath10k/htt_rx.c |    5 +++++
>>>>    1 file changed, 5 insertions(+)
>>>>
>>>> diff --git a/drivers/net/wireless/ath/ath10k/htt_rx.c b/drivers/net/wireless/ath/ath10k/htt_rx.c
>>>> index 9c782a4..baa1c44 100644
>>>> --- a/drivers/net/wireless/ath/ath10k/htt_rx.c
>>>> +++ b/drivers/net/wireless/ath/ath10k/htt_rx.c
>>>> @@ -97,6 +97,11 @@ static int __ath10k_htt_rx_ring_fill_n(struct ath10k_htt *htt, int num)
>>>>       }
>>>>
>>>>    fail:
>>>> +    /*
>>>> +     * Make sure the rx buffer is updated before available buffer
>>>> +     * index to avoid any potential rx ring corruption.
>>>> +     */
>>>> +    mb();
>>>>       *htt->rx_ring.alloc_idx.vaddr = __cpu_to_le32(idx);
>>>>       return ret;
>>>>    }
>>>>
>>>
>>>
>>
>> --
>> Ben Greear <greearb at candelatech.com>
>> Candela Technologies Inc  http://www.candelatech.com
>>
>

-- 
Ben Greear <greearb at candelatech.com>
Candela Technologies Inc  http://www.candelatech.com