linux-kernel - Re: [PATCH v2] net: stmmac: only enable DMA interrupts when ready

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Date:   Thu, 24 Feb 2022 15:53:33 +0300
From:   Denis Kirjanov <dkirjanov@...e.de>
To:     Vincent Whitchurch <vincent.whitchurch@...s.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>
Cc:     kernel@...s.com, Lars Persson <larper@...s.com>,
        Srinivas Kandagatla <srinivas.kandagatla@...com>,
        netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] net: stmmac: only enable DMA interrupts when ready



2/24/22 14:38, Vincent Whitchurch пишет:
> In this driver's ->ndo_open() callback, it enables DMA interrupts,
> starts the DMA channels, then requests interrupts with request_irq(),
> and then finally enables napi.
> 
> If RX DMA interrupts are received before napi is enabled, no processing
> is done because napi_schedule_prep() will return false.  If the network
> has a lot of broadcast/multicast traffic, then the RX ring could fill up
> completely before napi is enabled.  When this happens, no further RX
> interrupts will be delivered, and the driver will fail to receive any
> packets.
> 
> Fix this by only enabling DMA interrupts after all other initialization
> is complete.
> 
> Fixes: 523f11b5d4fd72efb ("net: stmmac: move hardware setup for stmmac_open to new function")
> Reported-by: Lars Persson <larper@...s.com>
> Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
> ---
>   .../net/ethernet/stmicro/stmmac/stmmac_main.c | 28 +++++++++++++++++--
>   1 file changed, 26 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 6708ca2aa4f7..43978558d6c0 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -2260,6 +2260,23 @@ static void stmmac_stop_tx_dma(struct stmmac_priv *priv, u32 chan)
>   	stmmac_stop_tx(priv, priv->ioaddr, chan);
>   }
>   
> +static void stmmac_enable_all_dma_irq(struct stmmac_priv *priv)
> +{
> +	u32 rx_channels_count = priv->plat->rx_queues_to_use;
> +	u32 tx_channels_count = priv->plat->tx_queues_to_use;
> +	u32 dma_csr_ch = max(rx_channels_count, tx_channels_count);
> +	u32 chan;
> +
> +	for (chan = 0; chan < dma_csr_ch; chan++) {
> +		struct stmmac_channel *ch = &priv->channel[chan];
> +		unsigned long flags;
> +
> +		spin_lock_irqsave(&ch->lock, flags);
> +		stmmac_enable_dma_irq(priv, priv->ioaddr, chan, 1, 1);
> +		spin_unlock_irqrestore(&ch->lock, flags);
> +	}
> +}
> +
>   /**
>    * stmmac_start_all_dma - start all RX and TX DMA channels
>    * @priv: driver private structure
> @@ -2902,8 +2919,10 @@ static int stmmac_init_dma_engine(struct stmmac_priv *priv)
>   		stmmac_axi(priv, priv->ioaddr, priv->plat->axi);
>   
>   	/* DMA CSR Channel configuration */
> -	for (chan = 0; chan < dma_csr_ch; chan++)
> +	for (chan = 0; chan < dma_csr_ch; chan++) {
>   		stmmac_init_chan(priv, priv->ioaddr, priv->plat->dma_cfg, chan);
Did you miss to take a channel lock?
> +		stmmac_disable_dma_irq(priv, priv->ioaddr, chan, 1, 1);
> +	}
>   
>   	/* DMA RX Channel Configuration */
>   	for (chan = 0; chan < rx_channels_count; chan++) {
> @@ -3759,6 +3778,7 @@ static int stmmac_open(struct net_device *dev)
>   
>   	stmmac_enable_all_queues(priv);
>   	netif_tx_start_all_queues(priv->dev);
> +	stmmac_enable_all_dma_irq(priv);
>   
>   	return 0;
>   
> @@ -6508,8 +6528,10 @@ int stmmac_xdp_open(struct net_device *dev)
>   	}
>   
>   	/* DMA CSR Channel configuration */
> -	for (chan = 0; chan < dma_csr_ch; chan++)
> +	for (chan = 0; chan < dma_csr_ch; chan++) {
>   		stmmac_init_chan(priv, priv->ioaddr, priv->plat->dma_cfg, chan);
> +		stmmac_disable_dma_irq(priv, priv->ioaddr, chan, 1, 1);
> +	}
>   
>   	/* Adjust Split header */
>   	sph_en = (priv->hw->rx_csum > 0) && priv->sph;
> @@ -6570,6 +6592,7 @@ int stmmac_xdp_open(struct net_device *dev)
>   	stmmac_enable_all_queues(priv);
>   	netif_carrier_on(dev);
>   	netif_tx_start_all_queues(dev);
> +	stmmac_enable_all_dma_irq(priv);
>   
>   	return 0;
>   
> @@ -7447,6 +7470,7 @@ int stmmac_resume(struct device *dev)
>   	stmmac_restore_hw_vlan_rx_fltr(priv, ndev, priv->hw);
>   
>   	stmmac_enable_all_queues(priv);
> +	stmmac_enable_all_dma_irq(priv);
>   
>   	mutex_unlock(&priv->lock);
>   	rtnl_unlock();