net: mhi: Allow decoupled MTU/MRU

MBIM protocol makes the mhi network interface asymmetric, ingress data
received from MHI is MBIM protocol, possibly containing multiple
aggregated IP packets, while egress data received from network stack is
IP protocol.

This changes allows a 'protocol' to specify its own MRU, that when
specified is used to allocate MHI RX buffers (skb).

For MBIM, Set the default MTU to 1500, which is the usual network MTU
for WWAN IP packets, and MRU to 3.5K (for allocation efficiency),
allowing skb to fit in an usual 4K page (including padding,
skb_shared_info, ...).

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/mhi/mhi.h b/drivers/net/mhi/mhi.h
index 12e7407d712ab57d14aa6d412cc33a75165c1780..1d0c499d27a32af3b875fd47aa1adb3c7290912e 100644 (file)
--- a/drivers/net/mhi/mhi.h
+++ b/drivers/net/mhi/mhi.h
@@ -29,6 +29,7 @@ struct mhi_net_dev {
        struct mhi_net_stats stats;
        u32 rx_queue_sz;
        int msg_enable;
+       unsigned int mru;
 };
 
 struct mhi_net_proto {

diff --git a/drivers/net/mhi/net.c b/drivers/net/mhi/net.c
index f59960876083f19c72931d88a88cf944dc222c31..5ec7a29f668d743a22727e504d0d6a81ef71c2ce 100644 (file)
--- a/drivers/net/mhi/net.c
+++ b/drivers/net/mhi/net.c
@@ -265,10 +265,12 @@ static void mhi_net_rx_refill_work(struct work_struct *work)
                                                      rx_refill.work);
        struct net_device *ndev = mhi_netdev->ndev;
        struct mhi_device *mdev = mhi_netdev->mdev;
-       int size = READ_ONCE(ndev->mtu);
        struct sk_buff *skb;
+       unsigned int size;
        int err;
 
+       size = mhi_netdev->mru ? mhi_netdev->mru : READ_ONCE(ndev->mtu);
+
        while (!mhi_queue_is_full(mdev, DMA_FROM_DEVICE)) {
                skb = netdev_alloc_skb(ndev, size);
                if (unlikely(!skb))

diff --git a/drivers/net/mhi/proto_mbim.c b/drivers/net/mhi/proto_mbim.c
index 5a176c3eed5331a1a42c11f39f3f8e025dc9c419..fc72b3f6ec9e169c64a71bae8303427854d59b61 100644 (file)
--- a/drivers/net/mhi/proto_mbim.c
+++ b/drivers/net/mhi/proto_mbim.c
@@ -26,6 +26,15 @@
 
 #define MBIM_NDP16_SIGN_MASK 0x00ffffff
 
+/* Usual WWAN MTU */
+#define MHI_MBIM_DEFAULT_MTU 1500
+
+/* 3500 allows to optimize skb allocation, the skbs will basically fit in
+ * one 4K page. Large MBIM packets will simply be split over several MHI
+ * transfers and chained by the MHI net layer (zerocopy).
+ */
+#define MHI_MBIM_DEFAULT_MRU 3500
+
 struct mbim_context {
        u16 rx_seq;
        u16 tx_seq;
@@ -281,6 +290,8 @@ static int mbim_init(struct mhi_net_dev *mhi_netdev)
                return -ENOMEM;
 
        ndev->needed_headroom = sizeof(struct mbim_tx_hdr);
+       ndev->mtu = MHI_MBIM_DEFAULT_MTU;
+       mhi_netdev->mru = MHI_MBIM_DEFAULT_MRU;
 
        return 0;
 }