Re: Help debugging iwldvm / ath10k stalls

[Emmanuel Grumbach <egrumbach@gmail.com>]

>>>>
>>>> Anyway, I don't buy the theory that this is caused by the firmware
>>>> going out to lunch.  The queues files in debugfs show the rx queue
>>>> chugging along and all of the tx queues have read_ptr == write_ptr.
>>>> Wireshark shows incoming broadcast traffic, too.  I'd guess that the
>>>> problem is more likely to be that the card is failing to wake up and
>>>> notice pending data in the TIM.
>>
>> Well... I might have been unclear here (I never know how much detail I should share with the recipient :)).
>> From your log it appears that the NIC is in power save. So we can't increment the write pointer of the Tx ring (add a packet for transmission). So we simply remember that we need to do so (increment the write pointer) and request a wakeup so that we will update the write pointer in the wakeup interrupt... which doesn't happen.
>> No power save - no need for wakeup interrupt.
> 
> I'm still unconvinced.  One of the tx queues actually has a both
> read_ptr and write_ptr incrementing once or twice per second even when
> I can't ping the gateway.  Can you point me at the right code or log
> stuff to look at?

drivers/net/wireless/iwlwifi/pcie/tx.c:
static void iwl_pcie_txq_inc_wr_ptr(struct iwl_trans *trans,
                                    struct iwl_txq *txq)
[snip]

                if (reg & CSR_UCODE_DRV_GP1_BIT_MAC_SLEEP) {
                        IWL_DEBUG_INFO(trans, "Tx queue %d requesting wakeup, GP1 = 0x%x\n",
                                       txq_id, reg);
                        iwl_set_bit(trans, CSR_GP_CNTRL,
                                    CSR_GP_CNTRL_REG_FLAG_MAC_ACCESS_REQ);
                        txq->need_update = true;
                        return;
                }
[snip]
}

ISR - drivers/net/wireless/iwlwifi/pcie/tx.c:
irqreturn_t iwl_pcie_irq_handler(int irq, void *dev_id)
{
[snip]
        /* uCode wakes up after power-down sleep */
        if (inta & CSR_INT_BIT_WAKEUP) {
                IWL_DEBUG_ISR(trans, "Wakeup interrupt\n");
                iwl_pcie_rxq_check_wrptr(trans);
                iwl_pcie_txq_check_wrptrs(trans);

                isr_stats->wakeup++;

                handled |= CSR_INT_BIT_WAKEUP;
        }
[snip]
}

drivers/net/wireless/iwlwifi/pcie/tx.c:
void iwl_pcie_txq_check_wrptrs(struct iwl_trans *trans)
{
        struct iwl_trans_pcie *trans_pcie = IWL_TRANS_GET_PCIE_TRANS(trans);
        int i;

        for (i = 0; i < trans->cfg->base_params->num_of_queues; i++) {
                struct iwl_txq *txq = &trans_pcie->txq[i];

                spin_lock_bh(&txq->lock);
                if (trans_pcie->txq[i].need_update) {
                        iwl_pcie_txq_inc_wr_ptr(trans, txq);
                        trans_pcie->txq[i].need_update = false;
                }
                spin_unlock_bh(&txq->lock);
        }
}

Note that the CMD queue (9 or 4 depending on your configuration) - uses another mechanism that is safer but consumes more power. This queue is intended for commands and not for real Tx packets.


> 
>>
>>>
>>> OTOH, with iwlwifi.11n_disable=4 (no rx A-MPDU), I seem to be doing
>>> pretty well.  I'll test a stock kernel configured like that for the
>>> next few days.
>>>
>>
>> That's interesting...
> 
> --Andy
>