Subject: Re: [PATCH] [v7] net: emac: emac gigabit ethernet controller driver

From: Timur Tabi <[email-masked]>
Date: Wed, 10 Aug 2016 11:38:53 -0500

Florian Fainelli wrote:
>> >Is there an easy way for me to stop the RX path before I set rxbuf_size?
>> >  Some netif_xxx function I can call?
> napi_disable() should take care of that.

It appears that if I call netif_stop_queue() *afer* calling 
napi_disable(), I get a hang and/or TX timeout.  Since emac_mac_down() 
does this:

	netif_stop_queue(netdev);
	napi_disable(&adpt->rx_q.napi);

I cannot call just napi_disable() in emac_change_mtu(), because when I 
then call emac_mac_down(), the first thing it does is call 
netif_stop_queue(), and that's when I timeout/hang.

Unfortunately, I cannot even do this:

	netif_stop_queue(netdev);
	napi_disable(&adpt->rx_q.napi);
	netif_stop_queue(netdev);
	napi_disable(&adpt->rx_q.napi);

Even though I've already called netif_stop_queue(), calling it again 
causes the timeout/hang.

Is this expected?  I never understood why I needed to call 
netif_stop_queue() before napi_disable().  I do see some drivers do not 
call netif_stop_queue().  I even saw a driver that calls them in reverse 
order, so I don't understand why that sequence breaks for me but not him.

-- 
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm
Technologies, Inc.  Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.