netdev - Re: [PATCH 1/2] [v4] net: emac: emac gigabit ethernet controller driver

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Date:	Tue, 10 May 2016 21:24:55 -0500
From:	Timur Tabi <timur@...eaurora.org>
To:	Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, sdharia@...eaurora.org,
	Shanker Donthineni <shankerd@...eaurora.org>,
	Greg Kroah-Hartman <greg@...ah.com>, vikrams@...eaurora.org,
	cov@...eaurora.org, gavidov@...eaurora.org,
	Rob Herring <robh+dt@...nel.org>, andrew@...n.ch,
	bjorn.andersson@...aro.org, Mark Langsdorf <mlangsdo@...hat.com>,
	Jon Masters <jcm@...hat.com>,
	Andy Gross <agross@...eaurora.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 1/2] [v4] net: emac: emac gigabit ethernet controller
 driver

Florian Fainelli wrote:
> The Ethernet MAC should be started in ndo_open() and stopped in
> ndo_close(), in between, there are link state changes, but you are not
> supposed to stop or start your Ethernet MAC and its DMA for instance
> during link change, if that is a HW requirement, your HW is pretty funky.

I think the problem is that the current driver seems to be too eager to 
start/stop the MAC.

Please take a look at emac_work_thread_link_check() at 
https://lkml.org/lkml/2016/4/13/670.  Every time the PHY link goes up, 
it does this:

if (phy->link_up) {
	if (netif_carrier_ok(netdev))
		goto link_task_done;

	pm_runtime_get_sync(netdev->dev.parent);
	netif_info(adpt, timer, adpt->netdev, "NIC Link is Up %s\n",
		   speed);

	emac_mac_start(adpt);
	netif_carrier_on(netdev);
	netif_wake_queue(netdev);


The call to emac_mac_start seems wrong to me here.

-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the
Code Aurora Forum, hosted by The Linux Foundation.