[U-Boot] [Patch V7 04/18] net/fm/eth: Use mb() to be compatible for both ARM and PowerPC

[Scott Wood]

On Fri, 2015-10-23 at 06:01 -0500, Hou Zhiqiang-B48286 wrote:
> 
> > -----Original Message-----
> > From: Wood Scott-B07421
> > Sent: 2015年10月23日 7:11
> > To: Gong Qianyu-B52263
> > Cc: u-boot at lists.denx.de; Hu Mingkai-B21284; Sun York-R58495; Hou
> > Zhiqiang-B48286; Xie Shaohui-B21989; Song Wenbin-B53747; Wood Scott-
> > B07421; Kushwaha Prabhakar-B32579; Wang Huan-B18965
> > Subject: Re: [Patch V7 04/18] net/fm/eth: Use mb() to be compatible for
> > both ARM and PowerPC
> > 
> > On Thu, 2015-10-22 at 18:46 +0800, Gong Qianyu wrote:
> > > From: Shaohui Xie <Shaohui.Xie at freescale.com>
> > > 
> > > Use mb() instead of sync() to be compatible for both ARM and PowerPC.
> > > 
> > > Signed-off-by: Shaohui Xie <Shaohui.Xie at freescale.com>
> > > Signed-off-by: Mingkai Hu <Mingkai.Hu at freescale.com>
> > > Signed-off-by: Gong Qianyu <Qianyu.Gong at freescale.com>
> > > ---
> > > V7:
> > >  - No change.
> > > V6:
> > >  - No change.
> > > V5:
> > >  - No change.
> > > V4:
> > >  - No change.
> > > V3:
> > >  - New patch. Separated from patch 'net: Move some header files to
> > include/'
> > > 
> > >  drivers/net/fm/eth.c | 14 +++++++-------
> > >  1 file changed, 7 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/drivers/net/fm/eth.c b/drivers/net/fm/eth.c index
> > > 368d554..ad02c66 100644
> > > --- a/drivers/net/fm/eth.c
> > > +++ b/drivers/net/fm/eth.c
> > > @@ -371,7 +371,7 @@ static void
> > > fmc_tx_port_graceful_stop_enable(struct
> > > fm_eth *fm_eth)
> > >       pram = fm_eth->tx_pram;
> > >       /* graceful stop transmission of frames */
> > >       setbits_be32(&pram->mode, PRAM_MODE_GRACEFUL_STOP);
> > > -     sync();
> > > +     mb();
> > >  }
> > > 
> > >  static void fmc_tx_port_graceful_stop_disable(struct fm_eth *fm_eth)
> > > @@ -381,7 +381,7 @@ static void
> > > fmc_tx_port_graceful_stop_disable(struct
> > > fm_eth *fm_eth)
> > >       pram = fm_eth->tx_pram;
> > >       /* re-enable transmission of frames */
> > >       clrbits_be32(&pram->mode, PRAM_MODE_GRACEFUL_STOP);
> > > -     sync();
> > > +     mb();
> > >  }
> > 
> > Why is it needed at all?  The I/O accessors should include the necessary
> > barriers.
> 
> The I/O accessors of powerpc does include the barrier, but it absents from 
> ARMs'.

Then fix ARM's accessors if they're missing barriers that are required.  But 
first, consider whether the barrier is required on ARM.  What is special 
about FM that it needs it where all other drivers don't?

-Scott