[PATCH v5 net-next 4/7] net: mvneta: Convert to be 64 bits compatible

Hi Jisheng,
 
 On jeu., d?c. 01 2016, Marcin Wojtas [off-list ref] 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?

I can confirm also that without this patch it just doesn't work.

Gregory

Best regards,
Marcin



2016-12-01 12:26 GMT+01:00 Jisheng Zhang [off-list ref]:

quoted

Hi Gregory, Marcin,

On Wed, 30 Nov 2016 22:42:49 +0100 Gregory CLEMENT wrote:

quoted

From: Marcin Wojtas <redacted>

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 <redacted>
Signed-off-by: Gregory CLEMENT <redacted>
---
 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?

quoted

+ */
+#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

-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com