linux-kernel - RE: [PATCH 02/14] net: axienet: Propagate failure of DMA descriptor setup

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Date:   Fri, 10 Jan 2020 17:53:08 +0000
From:   Radhey Shyam Pandey <radheys@...inx.com>
To:     Andre Przywara <andre.przywara@....com>,
        "David S . Miller" <davem@...emloft.net>
CC:     Michal Simek <michals@...inx.com>,
        Robert Hancock <hancock@...systems.ca>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 02/14] net: axienet: Propagate failure of DMA descriptor
 setup

> -----Original Message-----
> From: Radhey Shyam Pandey
> Sent: Friday, January 10, 2020 8:25 PM
> To: Andre Przywara <andre.przywara@....com>; David S . Miller
> <davem@...emloft.net>
> Cc: Michal Simek <michals@...inx.com>; Robert Hancock
> <hancock@...systems.ca>; netdev@...r.kernel.org; linux-arm-
> kernel@...ts.infradead.org; linux-kernel@...r.kernel.org
> Subject: RE: [PATCH 02/14] net: axienet: Propagate failure of DMA descriptor
> setup
> 
> > -----Original Message-----
> > From: Andre Przywara <andre.przywara@....com>
> > Sent: Friday, January 10, 2020 5:24 PM
> > To: David S . Miller <davem@...emloft.net>; Radhey Shyam Pandey
> > <radheys@...inx.com>
> > Cc: Michal Simek <michals@...inx.com>; Robert Hancock
> > <hancock@...systems.ca>; netdev@...r.kernel.org; linux-arm-
> > kernel@...ts.infradead.org; linux-kernel@...r.kernel.org
> > Subject: [PATCH 02/14] net: axienet: Propagate failure of DMA
> > descriptor setup
> >
> > When we fail allocating the DMA buffers in axienet_dma_bd_init(), we
> > report this error, but carry on with initialisation nevertheless.
> >
> > This leads to a kernel panic when the driver later wants to send a
> > packet, as it uses uninitialised data structures.
> >
> > Make the axienet_device_reset() routine return an error value, as it
> > contains the DMA buffer initialisation. Make sure we propagate the
> > error up the chain and eventually fail the driver initialisation, to
> > avoid relying on non-initialised buffers.
> >
> > Signed-off-by: Andre Przywara <andre.przywara@....com>
> Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@...inx.com>
> 
> > ---
> >  .../net/ethernet/xilinx/xilinx_axienet_main.c | 25
> > +++++++++++++------
> >  1 file changed, 18 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> > b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> > index 20746b801959..97482cf093ce 100644
> > --- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> > +++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> > @@ -437,9 +437,10 @@ static void axienet_setoptions(struct net_device
> > *ndev, u32 options)
> >  	lp->options |= options;
> >  }
> >
> > -static void __axienet_device_reset(struct axienet_local *lp)
> > +static int __axienet_device_reset(struct axienet_local *lp)
> >  {
> >  	u32 timeout;
> > +
> >  	/* Reset Axi DMA. This would reset Axi Ethernet core as well. The
> > reset
> >  	 * process of Axi DMA takes a while to complete as all pending
> >  	 * commands/transfers will be flushed or completed during this @@
> > -455,9 +456,11 @@ static void __axienet_device_reset(struct
> > axienet_local *lp)
> >  		if (--timeout == 0) {
> >  			netdev_err(lp->ndev, "%s: DMA reset timeout!\n",
> >  				   __func__);
> > -			break;
> > +			return -ETIMEDOUT;
> >  		}
> >  	}
> > +
> > +	return 0;
> >  }
> >
> >  /**
> > @@ -471,12 +474,15 @@ static void __axienet_device_reset(struct
> > axienet_local *lp)
> >   * Ethernet core. No separate hardware reset is done for the Axi Ethernet
> >   * core.
> >   */

Minor nit- we need to add descripton for return value.
drivers/net/ethernet/xilinx/xilinx_axienet_main.c:491: warning: 
No description found for return value of 'axienet_device_reset'

> > -static void axienet_device_reset(struct net_device *ndev)
> > +static int axienet_device_reset(struct net_device *ndev)
> >  {
> >  	u32 axienet_status;
> >  	struct axienet_local *lp = netdev_priv(ndev);
> > +	int ret;
> >
> > -	__axienet_device_reset(lp);
> > +	ret = __axienet_device_reset(lp);
> > +	if (ret)
> > +		return ret;
> >
> >  	lp->max_frm_size = XAE_MAX_VLAN_FRAME_SIZE;
> >  	lp->options |= XAE_OPTION_VLAN;
> > @@ -491,9 +497,11 @@ static void axienet_device_reset(struct
> > net_device
> > *ndev)
> >  			lp->options |= XAE_OPTION_JUMBO;
> >  	}
> >
> > -	if (axienet_dma_bd_init(ndev)) {
> > +	ret = axienet_dma_bd_init(ndev);
> > +	if (ret) {
> >  		netdev_err(ndev, "%s: descriptor allocation failed\n",
> >  			   __func__);
> > +		return ret;
> >  	}
> >
> >  	axienet_status = axienet_ior(lp, XAE_RCW1_OFFSET); @@ -518,6
> +526,8
> > @@ static void axienet_device_reset(struct net_device
> > *ndev)
> >  	axienet_setoptions(ndev, lp->options);
> >
> >  	netif_trans_update(ndev);
> > +
> > +	return 0;
> >  }
> >
> >  /**
> > @@ -921,8 +931,9 @@ static int axienet_open(struct net_device *ndev)
> >  	 */
> >  	mutex_lock(&lp->mii_bus->mdio_lock);
> >  	axienet_mdio_disable(lp);
> > -	axienet_device_reset(ndev);
> > -	ret = axienet_mdio_enable(lp);
> > +	ret = axienet_device_reset(ndev);
> > +	if (ret == 0)
> > +		ret = axienet_mdio_enable(lp);
> >  	mutex_unlock(&lp->mii_bus->mdio_lock);
> >  	if (ret < 0)
> >  		return ret;
> > --
> > 2.17.1