[PATCH v5 net-next 4/7] net: mvneta: Convert to be 64 bits compatible
Jisheng Zhang
jszhang at marvell.com
Thu Dec 1 04:16:48 PST 2016
On Thu, 1 Dec 2016 20:02:05 +0800 Jisheng Zhang wrote:
> Hi Marcin,
>
> On Thu, 1 Dec 2016 12:48:39 +0100 Marcin Wojtas wrote:
>
> > Hi Jisheng,
> >
> > Which baseline do you use?
> >
> > It took me really lot of time to catch why RX broke after rebase from
> > LKv4.1 to LKv4.4. Between those two, in commit:
> > 97303480753e ("arm64: Increase the max granular size")
> > L1_CACHE_BYTES for all ARMv8 platforms was increased to 128B and so
> > did NET_SKB_PAD.
> >
> > And 128 is more than the maximum that can fit into packet offset
> > [11:8]@0x1400. In such case this correction is needed. Did it answer
> > your doubts?
>
> That's key! Thanks a lot. In my repo, we don't have commit 97303480753e
> ("arm64: Increase the max granular size")
>
> I think it would be great if this information can be added into the commit
> msg.
>
> IIRC, arm64 maintainers considered to let L1_CACHE_BYTES the _minimum_ of
> cache line sizes of arm64. If that's implemented and merged, then we can
I just searched and found the email.
"We may have to revisit this logic and consider L1_CACHE_BYTES the
_minimum_ of cache line sizes in arm64 systems supported by the kernel.
Do you have any benchmarks on Cavium boards that would show significant
degradation with 64-byte L1_CACHE_BYTES vs 128?"
https://patchwork.kernel.org/patch/8634481/
> revert this patch later.
>
> Thanks,
> Jisheng
>
> >
> > Best regards,
> > Marcin
> >
> >
> >
> > 2016-12-01 12:26 GMT+01:00 Jisheng Zhang <jszhang at marvell.com>:
> > > Hi Gregory, Marcin,
> > >
> > > On Wed, 30 Nov 2016 22:42:49 +0100 Gregory CLEMENT wrote:
> > >
> > >> From: Marcin Wojtas <mw at semihalf.com>
> > >>
> > >> Prepare the mvneta driver in order to be usable on the 64 bits platform
> > >> such as the Armada 3700.
> > >>
> > >> [gregory.clement at free-electrons.com]: this patch was extract from a larger
> > >> one to ease review and maintenance.
> > >>
> > >> Signed-off-by: Marcin Wojtas <mw at semihalf.com>
> > >> Signed-off-by: Gregory CLEMENT <gregory.clement at free-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
> > > 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 at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
More information about the linux-arm-kernel
mailing list