On Mon, Jun 2, 2014 at 11:53 AM, Emmanuel Grumbach <egrumbach@xxxxxxxxx> wrote:
>
>>>>>
>>>>> 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.
If that's queue 4 in the debugfs tx_queues file, then I think that
that's the queue that keeps moving when the card is dead. I'll see if
I can improve the tx_queues file to show pending updates.
Yay troubleshooting old hardware.
--Andy
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