netdev - Re: [PATCH 4/5] net: macb: WoL support for GEM type of Ethernet controller

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Message-ID: <61762f4b-03fa-5484-334e-8515eed485e2@microchip.com>
Date:   Fri, 17 Apr 2020 19:14:19 +0200
From:   Nicolas Ferre <nicolas.ferre@...rochip.com>
To:     <linux-arm-kernel@...ts.infradead.org>, <netdev@...r.kernel.org>,
        "Claudiu Beznea" <claudiu.beznea@...rochip.com>,
        <harini.katakam@...inx.com>, <f.fainelli@...il.com>,
        <linux@...linux.org.uk>
CC:     <linux-kernel@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        <pthombar@...ence.com>, <sergio.prado@...abworks.com>,
        <antoine.tenart@...tlin.com>, <andrew@...n.ch>,
        <michal.simek@...inx.com>
Subject: Re: [PATCH 4/5] net: macb: WoL support for GEM type of Ethernet
 controller

On 16/04/2020 at 19:44, nicolas.ferre@...rochip.com wrote:
> From: Nicolas Ferre <nicolas.ferre@...rochip.com>
> 
> Adapt the Wake-on-Lan feature to the Cadence GEM Ethernet controller.
> This controller has different register layout and cannot be handled by
> previous code.
> We disable completely interrupts on all the queues but the queue 0.
> Handling of WoL interrupt is done in another interrupt handler
> positioned depending on the controller version used, just between
> suspend() and resume() calls.
> It allows to lower pressure on the generic interrupt hot path by
> removing the need to handle 2 tests for each IRQ: the first figuring out
> the controller revision, the second for actually knowing if the WoL bit
> is set.
> 
> Queue management in suspend()/resume() functions inspired from RFC patch
> by Harini Katakam <harinik@...inx.com>, thanks!
> 
> Signed-off-by: Nicolas Ferre <nicolas.ferre@...rochip.com>
> ---
>   drivers/net/ethernet/cadence/macb.h      |   3 +
>   drivers/net/ethernet/cadence/macb_main.c | 121 ++++++++++++++++++++---
>   2 files changed, 109 insertions(+), 15 deletions(-)

[..]

> @@ -4534,23 +4564,56 @@ static int __maybe_unused macb_suspend(struct device *dev)
>   	struct macb_queue *queue = bp->queues;
>   	unsigned long flags;
>   	unsigned int q;
> +	int err;
>   
>   	if (!netif_running(netdev))
>   		return 0;
>   
>   	if (bp->wol & MACB_WOL_ENABLED) {
> -		macb_writel(bp, IER, MACB_BIT(WOL));
> -		macb_writel(bp, WOL, MACB_BIT(MAG));
> -		enable_irq_wake(bp->queues[0].irq);
> -		netif_device_detach(netdev);
> -	} else {
> -		netif_device_detach(netdev);
> +		spin_lock_irqsave(&bp->lock, flags);
> +		/* Flush all status bits */
> +		macb_writel(bp, TSR, -1);
> +		macb_writel(bp, RSR, -1);
>   		for (q = 0, queue = bp->queues; q < bp->num_queues;
> -		     ++q, ++queue)
> -			napi_disable(&queue->napi);
> -		rtnl_lock();
> -		phylink_stop(bp->phylink);
> -		rtnl_unlock();
> +		     ++q, ++queue) {
> +			/* Disable all interrupts */
> +			queue_writel(queue, IDR, -1);
> +			queue_readl(queue, ISR);
> +			if (bp->caps & MACB_CAPS_ISR_CLEAR_ON_WRITE)
> +				queue_writel(queue, ISR, -1);
> +		}
> +		/* Change interrupt handler and
> +		 * Enable WoL IRQ on queue 0
> +		 */
> +		if (macb_is_gem(bp)) {
> +			devm_free_irq(dev, bp->queues[0].irq, bp->queues);
> +			err = devm_request_irq(dev, bp->queues[0].irq, gem_wol_interrupt,
> +					       IRQF_SHARED, netdev->name, bp->queues);
> +			if (err) {
> +				dev_err(dev,
> +					"Unable to request IRQ %d (error %d)\n",
> +					bp->queues[0].irq, err);
> +				return err;
> +			}
> +			queue_writel(bp->queues, IER, GEM_BIT(WOL));
> +			gem_writel(bp, WOL, MACB_BIT(MAG));
> +		} else {
> +			queue_writel(bp->queues, IER, MACB_BIT(WOL));
> +			macb_writel(bp, WOL, MACB_BIT(MAG));
> +		}
> +		spin_unlock_irqrestore(&bp->lock, flags);
> +
> +		enable_irq_wake(bp->queues[0].irq);
> +	}
> +
> +	netif_device_detach(netdev);
> +	for (q = 0, queue = bp->queues; q < bp->num_queues;
> +	     ++q, ++queue)
> +		napi_disable(&queue->napi);
> +
> +	if (!(bp->wol & MACB_WOL_ENABLED)) {
> +		phy_stop(netdev->phydev);
> +		phy_suspend(netdev->phydev);

Bug here: you must read:

		rtnl_lock();
		phylink_stop(bp->phylink);
		rtnl_unlock();

Instead of the 2 previous lines. I'll correct in v2.

Sorry for the regression.


>   		spin_lock_irqsave(&bp->lock, flags);
>   		macb_reset_hw(bp);
>   		spin_unlock_irqrestore(&bp->lock, flags);
> @@ -4575,20 +4638,48 @@ static int __maybe_unused macb_resume(struct device *dev)

[..]
BTW: I have issue having a real resume event from the phy with this 
series. I'm investigating that but didn't find anything for now.

Observation #1: when the WoL is not enabled, I don't have link issue. 
But the path in suspend/resume is far more intrusive in phy state.

Observation #2: when WoL is enabled, I need to do a full ifdown/ifup 
sequence for gain access again to the link:

ip link show eth0
2: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast 
state DOWN mode DEFAULT group default qlen 1000
     link/ether 54:10:ec:be:50:b0 brd ff:ff:ff:ff:ff:ff

ifdown eth0 && ifup eth0

ip link show eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast 
state UP mode DEFAULT group default qlen 1000
     link/ether 54:10:ec:be:50:b0 brd ff:ff:ff:ff:ff:ff

Observation #3: I didn't experience this behavior while playing with the 
WoL on my 4.19 kernel before porting to Mainline.

Best regards,
-- 
Nicolas Ferre