[PATCH v3 net] net: stmmac: dwmac4: extend timeout for VLAN Tag register busy bit check

[Shenwei Wang]

> -----Original Message-----
> From: Serge Semin <fancer.lancer at gmail.com>
> Sent: Tuesday, September 24, 2024 2:30 AM
> To: Shenwei Wang <shenwei.wang at nxp.com>
> Cc: David S. Miller <davem at davemloft.net>; Eric Dumazet
> <edumazet at google.com>; Jakub Kicinski <kuba at kernel.org>; Paolo Abeni
> <pabeni at redhat.com>; Maxime Coquelin <mcoquelin.stm32 at gmail.com>;
> horms at kernel.org; Alexandre Torgue <alexandre.torgue at foss.st.com>; Jose
> Abreu <joabreu at synopsys.com>; Ong Boon Leong <boon.leong.ong at intel.com>;
> Wong Vee Khee <vee.khee.wong at intel.com>; Chuah Kim Tatt
> <kim.tatt.chuah at intel.com>; netdev at vger.kernel.org; linux-stm32 at st-md-
> mailman.stormreply.com; linux-arm-kernel at lists.infradead.org;
> imx at lists.linux.dev; dl-linux-imx <linux-imx at nxp.com>; Andrew Lunn
> <andrew at lunn.ch>
> Subject: [EXT] Re: [PATCH v3 net] net: stmmac: dwmac4: extend timeout for
> VLAN Tag register busy bit check
> >
> > Overnight testing revealed that when EEE is active, the busy bit can
> > remain set for up to approximately 300ms. The new 500ms timeout
> > provides a safety margin.
> >
> > Fixes: ed64639bc1e0 ("net: stmmac: Add support for VLAN Rx filtering")
> > Signed-off-by: Shenwei Wang <shenwei.wang at nxp.com>
> > Reviewed-by: Andrew Lunn <andrew at lunn.ch>
> 
> > Reviewed-by: Serge Semin <fancer.lancer at gmail.com>
> 
> Please note, you can't add the R-b tag without explicitly getting one from the
> reviewer/maintainer/etc. Please read the chapter "When to use Acked-by:, Cc:,
> and Co-developed-by:" in Documentation/process/submitting-patches.rst
> 

I apologize, Serge. 
I made an error in how I utilized the r-b function here. My intention was to explicitly 
include you in the next version of the patch.

Thanks,
Shenwei

> > ---
> > Changes in V3:
> >  - re-org the error-check flow per Serge's review.
> >
> > Changes in v2:
> >  - replace the udelay with readl_poll_timeout per Simon's review.
> >
> > ---
> >  .../net/ethernet/stmicro/stmmac/dwmac4_core.c  | 18
> > +++++++++---------
> >  1 file changed, 9 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
> > b/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
> > index a1858f083eef..0d27dd71b43e 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
> > @@ -14,6 +14,7 @@
> >  #include <linux/slab.h>
> >  #include <linux/ethtool.h>
> >  #include <linux/io.h>
> > +#include <linux/iopoll.h>
> >  #include "stmmac.h"
> >  #include "stmmac_pcs.h"
> >  #include "dwmac4.h"
> > @@ -471,7 +472,7 @@ static int dwmac4_write_vlan_filter(struct net_device
> *dev,
> >                                   u8 index, u32 data)  {
> >       void __iomem *ioaddr = (void __iomem *)dev->base_addr;
> > -     int i, timeout = 10;
> > +     int ret;
> >       u32 val;
> >
> >       if (index >= hw->num_vlan)
> > @@ -487,16 +488,15 @@ static int dwmac4_write_vlan_filter(struct
> > net_device *dev,
> >
> >       writel(val, ioaddr + GMAC_VLAN_TAG);
> >
> > -     for (i = 0; i < timeout; i++) {
> > -             val = readl(ioaddr + GMAC_VLAN_TAG);
> > -             if (!(val & GMAC_VLAN_TAG_CTRL_OB))
> > -                     return 0;
> > -             udelay(1);
> 
> > +     ret = readl_poll_timeout(ioaddr + GMAC_VLAN_TAG, val,
> > +                              !(val & GMAC_VLAN_TAG_CTRL_OB),
> > +                              1000, 500000); //Timeout 500ms
> 
> Please drop the comment at the end of the statement. First of all the
> C++-style comments are discouraged to be used in the kernel code except
> when in the block of the SPDX licence identifier, or when documenting structs in
> headers. Secondly the tail-comments are discouraged either (see
> Documentation/process/maintainer-tip.rst - yes, it's for tip-tree, but the rule see
> informally applicable for the entire kernel). Thirdly the comment is pointless here
> since the literal
> 500000 means exactly that.
> 
> -Serge(y)
> 
> > +     if (ret) {
> > +             netdev_err(dev, "Timeout accessing MAC_VLAN_Tag_Filter\n");
> > +             return -EBUSY;
> >       }
> >
> > -     netdev_err(dev, "Timeout accessing MAC_VLAN_Tag_Filter\n");
> > -
> > -     return -EBUSY;
> > +     return 0;
> >  }
> >
> >  static int dwmac4_add_hw_vlan_rx_fltr(struct net_device *dev,
> > --
> > 2.34.1
> >