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SubjectRE: [RFC][PATCH 06/10] fec: fix uninitialized rx buffer usage
Date
From
Sascha,

> -----Original Message-----
> From: Sascha Hauer [mailto:s.hauer@pengutronix.de]
> Sent: Friday, December 04, 2009 5:14 AM
> To: Amit Kucheria
> Cc: List Linux Kernel; Herring Robert-RA7055; David S.
> Miller; netdev@vger.kernel.org;
> linux-arm-kernel@lists.infradead.org;
> valentin.longchamp@epfl.ch; daniel@caiaq.de;
> grant.likely@secretlab.ca; Nguyen Dinh-R00091
> Subject: Re: [RFC][PATCH 06/10] fec: fix uninitialized rx buffer usage
>
> On Fri, Dec 04, 2009 at 04:47:06AM +0200, Amit Kucheria wrote:
> > From: Rob Herring <r.herring@freescale.com>
> >
> > The fec driver was enabling receive buffer descriptor
> without allocating
> > the buffers. Make sure the buffer descriptors are initialized to not
> > start receiving packets.
> >
> > Signed-off-by: Rob Herring <r.herring@freescale.com>
> > Signed-off-by: Amit Kucheria <amit.kucheria@canonical.com>
> > Cc: David S. Miller <davem@davemloft.net>
> > Cc: netdev@vger.kernel.org
> > ---
> > drivers/net/fec.c | 57
> +++++++++++++++++++++++++++--------------------------
> > 1 files changed, 29 insertions(+), 28 deletions(-)
> >
> > diff --git a/drivers/net/fec.c b/drivers/net/fec.c
> > index 16a1d58..9a8743d 100644
> > --- a/drivers/net/fec.c
> > +++ b/drivers/net/fec.c
> > @@ -1658,6 +1658,7 @@ static int fec_enet_init(struct
> net_device *dev, int index)
> > {
> > struct fec_enet_private *fep = netdev_priv(dev);
> > struct bufdesc *cbd_base;
> > + struct bufdesc *bdp;
> > int i;
> >
> > /* Allocate memory for buffer descriptors. */
> > @@ -1710,6 +1711,34 @@ static int fec_enet_init(struct
> net_device *dev, int index)
> > /* Set MII speed to 2.5 MHz */
> > fep->phy_speed = ((((clk_get_rate(fep->clk) / 2 + 4999999)
> > / 2500000) / 2) & 0x3F) << 1;
> > +
> > + /* Initialize the receive buffer descriptors. */
> > + bdp = fep->rx_bd_base;
> > + for (i = 0; i < RX_RING_SIZE; i++) {
> > +
> > + /* Initialize the BD for every fragment in the page. */
> > + bdp->cbd_sc = 0;
> > + bdp++;
> > + }
> > +
> > + /* Set the last buffer to wrap */
> > + bdp--;
> > + bdp->cbd_sc |= BD_SC_WRAP;
> > +
> > + /* ...and the same for transmit */
> > + bdp = fep->tx_bd_base;
> > + for (i = 0; i < TX_RING_SIZE; i++) {
> > +
> > + /* Initialize the BD for every fragment in the page. */
> > + bdp->cbd_sc = 0;
> > + bdp->cbd_bufaddr = 0;
> > + bdp++;
> > + }
> > +
> > + /* Set the last buffer to wrap */
> > + bdp--;
> > + bdp->cbd_sc |= BD_SC_WRAP;
> > +
> > fec_restart(dev, 0);
>
> I do not really understand why this patch is needed. You move
> the buffer
> initialisation from fec_restart to fec_enet_init, but fec_restart is
> called directly after the initialisation, so this shouldn't
> change much.
>
> I don't need this patch on my boards, so I wonder what is really going
> wrong here.

It is because open also calls fec_restart after the rx buffers are
allocated. With the code in fec_restart, it zeroes out the buffer
descriptors that have just been setup. I can't explain how it would work
for you.

Regards,
Rob

>
> Sascha
>
>
> >
> > /* Queue up command to detect the PHY and initialize the
> > @@ -1730,7 +1759,6 @@ static void
> > fec_restart(struct net_device *dev, int duplex)
> > {
> > struct fec_enet_private *fep = netdev_priv(dev);
> > - struct bufdesc *bdp;
> > int i;
> >
> > /* Whack a reset. We should wait for this. */
> > @@ -1768,33 +1796,6 @@ fec_restart(struct net_device *dev,
> int duplex)
> > }
> > }
> >
> > - /* Initialize the receive buffer descriptors. */
> > - bdp = fep->rx_bd_base;
> > - for (i = 0; i < RX_RING_SIZE; i++) {
> > -
> > - /* Initialize the BD for every fragment in the page. */
> > - bdp->cbd_sc = BD_ENET_RX_EMPTY;
> > - bdp++;
> > - }
> > -
> > - /* Set the last buffer to wrap */
> > - bdp--;
> > - bdp->cbd_sc |= BD_SC_WRAP;
> > -
> > - /* ...and the same for transmit */
> > - bdp = fep->tx_bd_base;
> > - for (i = 0; i < TX_RING_SIZE; i++) {
> > -
> > - /* Initialize the BD for every fragment in the page. */
> > - bdp->cbd_sc = 0;
> > - bdp->cbd_bufaddr = 0;
> > - bdp++;
> > - }
> > -
> > - /* Set the last buffer to wrap */
> > - bdp--;
> > - bdp->cbd_sc |= BD_SC_WRAP;
> > -
> > /* Enable MII mode */
> > if (duplex) {
> > /* MII enable / FD enable */
> > --
> > 1.6.3.3
> >
> >
>
> --
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> |
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