Re: [PATCH v2 2/2] net: mvneta: improve suspend/resume

[Russell King - ARM Linux]

On Fri, Mar 30, 2018 at 06:36:15PM +0800, Jisheng Zhang wrote:
> Current suspend/resume implementation reuses the mvneta_open() and
> mvneta_close(), but it could be optimized to take only necessary
> actions during suspend/resume.
> 
> One obvious problem of current implementation is: after hundreds of
> system suspend/resume cycles, the resume of mvneta could fail due to
> fragmented dma coherent memory. After this patch, the non-necessary
> memory alloc/free is optimized out.

I don't think you've properly tested this.  Please ensure that you test
patches with the appropriate debug options enabled.

> @@ -4586,16 +4586,43 @@ static int mvneta_remove(struct platform_device *pdev)
>  #ifdef CONFIG_PM_SLEEP
>  static int mvneta_suspend(struct device *device)
>  {
> +	int queue;
>  	struct net_device *dev = dev_get_drvdata(device);
>  	struct mvneta_port *pp = netdev_priv(dev);
>  
> -	rtnl_lock();
> -	if (netif_running(dev))
> -		mvneta_stop(dev);
> -	rtnl_unlock();
...
> +	mvneta_stop_dev(pp);

You're removing the rtnl_lock() that I introduced in 3b8bc67413de
("net: mvneta: ensure PM paths take the rtnl lock") which is necessary
to provide phylink with consistent locking.  mvneta_stop_dev() calls
phylink_stop() which will check that the rtnl lock is held, and will
print a warning if it isn't.

Your patch will cause a regression here.

> +
> +	for (queue = 0; queue < rxq_number; queue++) {
> +		struct mvneta_rx_queue *rxq = &pp->rxqs[queue];
> +
> +		mvneta_rxq_drop_pkts(pp, rxq);
> +	}
> +
> +	for (queue = 0; queue < txq_number; queue++) {
> +		struct mvneta_tx_queue *txq = &pp->txqs[queue];
> +
> +		mvneta_txq_hw_deinit(pp, txq);
> +	}
> +
> +clean_exit:
>  	netif_device_detach(dev);
>  	clk_disable_unprepare(pp->clk_bus);
>  	clk_disable_unprepare(pp->clk);
> +
>  	return 0;
>  }
>  
> @@ -4604,7 +4631,7 @@ static int mvneta_resume(struct device *device)
>  	struct platform_device *pdev = to_platform_device(device);
>  	struct net_device *dev = dev_get_drvdata(device);
>  	struct mvneta_port *pp = netdev_priv(dev);
> -	int err;
> +	int err, queue;
>  
>  	clk_prepare_enable(pp->clk);
>  	if (!IS_ERR(pp->clk_bus))
> @@ -4626,12 +4653,36 @@ static int mvneta_resume(struct device *device)
>  	}
>  
>  	netif_device_attach(dev);
> -	rtnl_lock();
> -	if (netif_running(dev)) {
> -		mvneta_open(dev);
> -		mvneta_set_rx_mode(dev);
...
>  	}
> -	rtnl_unlock();
...
> +	mvneta_start_dev(pp);

Same applies here.

-- 
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