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Date:   Thu, 1 Dec 2016 19:41:47 +0800
From:   Jisheng Zhang <jszhang@...vell.com>
To:     Gregory CLEMENT <gregory.clement@...e-electrons.com>,
        Marcin Wojtas <mw@...ihalf.com>
CC:     Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        Andrew Lunn <andrew@...n.ch>,
        Jason Cooper <jason@...edaemon.net>,
        Arnd Bergmann <arnd@...db.de>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Dmitri Epshtein <dima@...vell.com>,
        Nadav Haklai <nadavh@...vell.com>,
        Yelena Krivosheev <yelena@...vell.com>,
        "David S. Miller" <davem@...emloft.net>,
        <linux-arm-kernel@...ts.infradead.org>,
        "Sebastian Hesselbarth" <sebastian.hesselbarth@...il.com>
Subject: Re: [PATCH v5 net-next 4/7] net: mvneta: Convert to be 64 bits
 compatible

On Thu, 1 Dec 2016 19:26:04 +0800
Jisheng Zhang <jszhang@...vell.com> wrote:

> Hi Gregory, Marcin,
> 
> On Wed, 30 Nov 2016 22:42:49 +0100 Gregory CLEMENT wrote:
> 
> > From: Marcin Wojtas <mw@...ihalf.com>
> > 
> > Prepare the mvneta driver in order to be usable on the 64 bits platform
> > such as the Armada 3700.
> > 
> > [gregory.clement@...e-electrons.com]: this patch was extract from a larger
> > one to ease review and maintenance.
> > 
> > Signed-off-by: Marcin Wojtas <mw@...ihalf.com>
> > Signed-off-by: Gregory CLEMENT <gregory.clement@...e-electrons.com>
> > ---
> >  drivers/net/ethernet/marvell/mvneta.c | 17 ++++++++++++++++-
> >  1 file changed, 16 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> > index 92b9af14c352..8ef03fb69bcd 100644
> > --- a/drivers/net/ethernet/marvell/mvneta.c
> > +++ b/drivers/net/ethernet/marvell/mvneta.c
> > @@ -296,6 +296,12 @@
> >  /* descriptor aligned size */
> >  #define MVNETA_DESC_ALIGNED_SIZE	32
> >  
> > +/* Number of bytes to be taken into account by HW when putting incoming data
> > + * to the buffers. It is needed in case NET_SKB_PAD exceeds maximum packet
> > + * offset supported in MVNETA_RXQ_CONFIG_REG(q) registers.  
> 
> We also brought up this driver on 64bit platforms, we doesn't have this
> patch. Maybe I'm wrong, I'm trying to understand why we need this
> modification. Let's assume the NET_SKB_PAD is 64B, we call
> mvneta_rxq_offset_set(pp, rxq, 64),
> 
> {
>         u32 val;
> 
>         val = mvreg_read(pp, MVNETA_RXQ_CONFIG_REG(rxq->id));
>         val &= ~MVNETA_RXQ_PKT_OFFSET_ALL_MASK;
> 
>         /* Offset is in */
>         val |= MVNETA_RXQ_PKT_OFFSET_MASK(offset >> 3);
> // then this will be "val |= 8;" it doesn't exceeds the max offset of

sorry, this will be "val |= MVNETA_RXQ_PKT_OFFSET_MASK(8);"

> MVNETA_RXQ_CONFIG_REG(q) register.
> 
> Could you please kindly point out where I am wrong?
> 
> > + */
> > +#define MVNETA_RX_PKT_OFFSET_CORRECTION		64
> > +
> >  #define MVNETA_RX_PKT_SIZE(mtu) \
> >  	ALIGN((mtu) + MVNETA_MH_SIZE + MVNETA_VLAN_TAG_LEN + \
> >  	      ETH_HLEN + ETH_FCS_LEN,			     \
> > @@ -416,6 +422,7 @@ struct mvneta_port {
> >  	u64 ethtool_stats[ARRAY_SIZE(mvneta_statistics)];
> >  
> >  	u32 indir[MVNETA_RSS_LU_TABLE_SIZE];
> > +	u16 rx_offset_correction;
> >  };
> >  
> >  /* The mvneta_tx_desc and mvneta_rx_desc structures describe the
> > @@ -1807,6 +1814,7 @@ static int mvneta_rx_refill(struct mvneta_port *pp,
> >  		return -ENOMEM;
> >  	}
> >  
> > +	phys_addr += pp->rx_offset_correction;
> >  	mvneta_rx_desc_fill(rx_desc, phys_addr, data, rxq);
> >  	return 0;
> >  }
> > @@ -2782,7 +2790,7 @@ static int mvneta_rxq_init(struct mvneta_port *pp,
> >  	mvreg_write(pp, MVNETA_RXQ_SIZE_REG(rxq->id), rxq->size);
> >  
> >  	/* Set Offset */
> > -	mvneta_rxq_offset_set(pp, rxq, NET_SKB_PAD);
> > +	mvneta_rxq_offset_set(pp, rxq, NET_SKB_PAD - pp->rx_offset_correction);
> >  
> >  	/* Set coalescing pkts and time */
> >  	mvneta_rx_pkts_coal_set(pp, rxq, rxq->pkts_coal);
> > @@ -4033,6 +4041,13 @@ static int mvneta_probe(struct platform_device *pdev)
> >  
> >  	pp->rxq_def = rxq_def;
> >  
> > +	/* Set RX packet offset correction for platforms, whose
> > +	 * NET_SKB_PAD, exceeds 64B. It should be 64B for 64-bit
> > +	 * platforms and 0B for 32-bit ones.  
> 
> Even we need this patch, I'm not sure this last comment is correct or not.
> NET_SKB_PAD is defined as:
> 
> #define NET_SKB_PAD     max(32, L1_CACHE_BYTES)
> 
> we have 64B cacheline 32bit platforms, on this platforms, the NET_SKB_PAD
> should be 64B as well.
> 
> Thanks,
> Jisheng
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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