Subject: Re: [PATCH v2] net: stmmac: Move debugfs init/exit to ->probe()/->remove()

From: Thierry Reding <[email-masked]>
Date: Wed, 28 Nov 2018 10:41:19 +0100

On Wed, Nov 28, 2018 at 09:38:32AM +0000, Jose Abreu wrote:
> On 27-11-2018 13:21, Thierry Reding wrote:
> > From: Thierry Reding <[email-masked]>
> >
> > Setting up and tearing down debugfs is current unbalanced, as seen by
> > this error during resume from suspend:
> >
> >     [  752.134067] dwc-eth-dwmac 2490000.ethernet eth0: ERROR failed to create debugfs directory
> >     [  752.134347] dwc-eth-dwmac 2490000.ethernet eth0: stmmac_hw_setup: failed debugFS registration
> >
> > The imbalance happens because the driver creates the debugfs hierarchy
> > when the device is opened and tears it down when the device is closed.
> > There's little gain in that, and it could be argued that it is even
> > surprising because it's not usually done for other devices. Fix the
> > imbalance by moving the debugfs creation and teardown to the driver's
> > ->probe() and ->remove() implementations instead.
> >
> > Note that the ring descriptors cannot be read while the interface is
> > down, so make sure to return an empty file when the descriptors_status
> > debugfs file is read.
> >
> > Signed-off-by: Thierry Reding <[email-masked]>
> > ---
> > This applies on top of net-next.
> >
> > Changes in v2:
> > - avoid access to ring descriptors when interface is down
> >
> >  .../net/ethernet/stmicro/stmmac/stmmac_main.c | 23 +++++++++++--------
> >  1 file changed, 13 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > index 076a8be18d67..5551fead8f66 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > @@ -2550,12 +2550,6 @@ static int stmmac_hw_setup(struct net_device *dev, bool init_ptp)
> >  			netdev_warn(priv->dev, "PTP init failed\n");
> >  	}
> >  
> > -#ifdef CONFIG_DEBUG_FS
> > -	ret = stmmac_init_fs(dev);
> > -	if (ret < 0)
> > -		netdev_warn(priv->dev, "%s: failed debugFS registration\n",
> > -			    __func__);
> > -#endif
> >  	priv->tx_lpi_timer = STMMAC_DEFAULT_TWT_LS;
> >  
> >  	if (priv->use_riwt) {
> > @@ -2756,10 +2750,6 @@ static int stmmac_release(struct net_device *dev)
> >  
> >  	netif_carrier_off(dev);
> >  
> > -#ifdef CONFIG_DEBUG_FS
> > -	stmmac_exit_fs(dev);
> > -#endif
> > -
> >  	stmmac_release_ptp(priv);
> >  
> >  	return 0;
> > @@ -3899,6 +3889,9 @@ static int stmmac_sysfs_ring_read(struct seq_file *seq, void *v)
> >  	u32 tx_count = priv->plat->tx_queues_to_use;
> >  	u32 queue;
> >  
> > +	if ((dev->flags & IFF_UP) == 0)
> 
> I tried looking for an helper to check if interface is open but
> couldn't find one so I guess this is the right thing to do.

Yeah, I had done the same thing and came up empty-handed.

> Acked-by: Jose Abreu <[email-masked]>

Thanks!
Thierry