Re: [RFC v3 1/2] iwlwifi: pcie: allow to build an A-MSDU using TSO core

When the op_mode sends an skb whose payload is bigger than
MSS, PCIe will create an A-MSDU out of it. PCIe assumes
that the skb that is coming from the op_mode can fit in one
A-MSDU. It is the op_mode's responsibility to make sure
that this guarantee holds.

Additional headers need to be built for the subframes.
The TSO core code takes care of the IP / TCP headers and
the driver takes care of the 802.11 subframe headers.

These headers are stored on a per-cpu page that is re-used
for all the packets handled on that same CPU. Each skb
holds a reference to that page and releases the page when
it is reclaimed. When the page gets full, it is released
and a new one is allocated.

Since any SKB that doesn't go through the fast-xmit path
of mac80211 will be segmented, we can assume here that the
packet is not WEP / TKIP and has a proper SNAP header.

Signed-off-by: Emmanuel Grumbach <redacted>
---
 drivers/net/wireless/iwlwifi/iwl-devtrace-data.h |  16 ++
 drivers/net/wireless/iwlwifi/iwl-trans.h         |   6 +-
 drivers/net/wireless/iwlwifi/pcie/internal.h     |   7 +
 drivers/net/wireless/iwlwifi/pcie/trans.c        |  20 +-
 drivers/net/wireless/iwlwifi/pcie/tx.c           | 286 ++++++++++++++++++++++-
 5 files changed, 329 insertions(+), 6 deletions(-)

diff --git a/drivers/net/wireless/iwlwifi/iwl-devtrace-data.h b/drivers/net/wireless/iwlwifi/iwl-devtrace-data.h
index 71a78ce..59d9edf 100644
--- a/drivers/net/wireless/iwlwifi/iwl-devtrace-data.h
+++ b/drivers/net/wireless/iwlwifi/iwl-devtrace-data.h

@@ -51,6 +51,22 @@ TRACE_EVENT(iwlwifi_dev_tx_data,
 	TP_printk("[%s] TX frame data", __get_str(dev))
 );
 
+TRACE_EVENT(iwlwifi_dev_tx_tso_chunk,
+	TP_PROTO(const struct device *dev,
+		 u8 *data_src, size_t data_len),
+	TP_ARGS(dev, data_src, data_len),
+	TP_STRUCT__entry(
+		DEV_ENTRY
+
+		__dynamic_array(u8, data, data_len)
+	),
+	TP_fast_assign(
+		DEV_ASSIGN;
+		memcpy(__get_dynamic_array(data), data_src, data_len);
+	),
+	TP_printk("[%s] TX frame data", __get_str(dev))
+);
+
 TRACE_EVENT(iwlwifi_dev_rx_data,
 	TP_PROTO(const struct device *dev,
 		 const struct iwl_trans *trans,

diff --git a/drivers/net/wireless/iwlwifi/iwl-trans.h b/drivers/net/wireless/iwlwifi/iwl-trans.h
index 0ceff69..6919243 100644
--- a/drivers/net/wireless/iwlwifi/iwl-trans.h
+++ b/drivers/net/wireless/iwlwifi/iwl-trans.h

@@ -379,7 +379,11 @@ static inline void iwl_free_rxb(struct iwl_rx_cmd_buffer *r)
 }
 
 #define MAX_NO_RECLAIM_CMDS	6
-
+/*
+ * The first entry in driver_data array in ieee80211_tx_info
+ * that can be used by the transport.
+ */
+#define IWL_FIRST_DRIVER_DATA 2
 #define IWL_MASK(lo, hi) ((1 << (hi)) | ((1 << (hi)) - (1 << (lo))))
 
 /*

diff --git a/drivers/net/wireless/iwlwifi/pcie/internal.h b/drivers/net/wireless/iwlwifi/pcie/internal.h
index be168d1..7da5643 100644
--- a/drivers/net/wireless/iwlwifi/pcie/internal.h
+++ b/drivers/net/wireless/iwlwifi/pcie/internal.h

@@ -295,6 +295,11 @@ iwl_pcie_get_scratchbuf_dma(struct iwl_txq *txq, int idx)
 	       sizeof(struct iwl_pcie_txq_scratch_buf) * idx;
 }
 
+struct iwl_tso_hdr_page {
+	struct page *page;
+	u8 *pos;
+};
+
 /**
  * struct iwl_trans_pcie - PCIe transport specific data
  * @rxq: all the RX queue data

@@ -332,6 +337,8 @@ struct iwl_trans_pcie {
 	struct net_device napi_dev;
 	struct napi_struct napi;
 
+	struct __percpu iwl_tso_hdr_page *tso_hdr_page;
+
 	/* INT ICT Table */
 	__le32 *ict_tbl;
 	dma_addr_t ict_tbl_dma;

diff --git a/drivers/net/wireless/iwlwifi/pcie/trans.c b/drivers/net/wireless/iwlwifi/pcie/trans.c
index a275318..5bd678b 100644
--- a/drivers/net/wireless/iwlwifi/pcie/trans.c
+++ b/drivers/net/wireless/iwlwifi/pcie/trans.c

@@ -1601,6 +1601,7 @@ static void iwl_trans_pcie_configure(struct iwl_trans *trans,
 void iwl_trans_pcie_free(struct iwl_trans *trans)
 {
 	struct iwl_trans_pcie *trans_pcie = IWL_TRANS_GET_PCIE_TRANS(trans);
+	int i;
 
 #ifdef CPTCFG_IWLWIFI_PLATFORM_DATA
 	/* Make sure the device is on before calling pci functions again.

@@ -1631,6 +1632,15 @@ void iwl_trans_pcie_free(struct iwl_trans *trans)
 
 	iwl_pcie_free_fw_monitor(trans);
 
+	for_each_possible_cpu(i) {
+		struct iwl_tso_hdr_page *p =
+			per_cpu_ptr(trans_pcie->tso_hdr_page, i);
+
+		if (p->page)
+			__free_pages(p->page, 0);
+	}
+
+	free_percpu(trans_pcie->tso_hdr_page);
 	iwl_trans_free(trans);
 }
 

@@ -2822,7 +2832,7 @@ struct iwl_trans *iwl_trans_pcie_alloc(struct pci_dev *pdev,
 	struct iwl_trans_pcie *trans_pcie;
 	struct iwl_trans *trans;
 	u16 pci_cmd;
-	int ret;
+	int i, ret;
 
 	trans = iwl_trans_alloc(sizeof(struct iwl_trans_pcie),
 				&pdev->dev, cfg, &trans_ops_pcie, 0);

@@ -2839,6 +2849,14 @@ struct iwl_trans *iwl_trans_pcie_alloc(struct pci_dev *pdev,
 	spin_lock_init(&trans_pcie->ref_lock);
 	mutex_init(&trans_pcie->mutex);
 	init_waitqueue_head(&trans_pcie->ucode_write_waitq);
+	trans_pcie->tso_hdr_page = alloc_percpu(struct iwl_tso_hdr_page);

+	}
+
 
 	ret = pci_enable_device(pdev);
 	if (ret)

diff --git a/drivers/net/wireless/iwlwifi/pcie/tx.c b/drivers/net/wireless/iwlwifi/pcie/tx.c
index c8f3967..14d7218 100644
--- a/drivers/net/wireless/iwlwifi/pcie/tx.c
+++ b/drivers/net/wireless/iwlwifi/pcie/tx.c

@@ -30,6 +30,7 @@
 #include <linux/etherdevice.h>
 #include <linux/slab.h>
 #include <linux/sched.h>
+#include <net/tso.h>
 
 #include "iwl-debug.h"
 #include "iwl-csr.h"

@@ -592,8 +593,19 @@ static void iwl_pcie_txq_unmap(struct iwl_trans *trans, int txq_id)
 
 	spin_lock_bh(&txq->lock);
 	while (q->write_ptr != q->read_ptr) {
+		struct sk_buff *skb = txq->entries[q->read_ptr].skb;
+		struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+
 		IWL_DEBUG_TX_REPLY(trans, "Q %d Free %d\n",
 				   txq_id, q->read_ptr);
+
+		if (info->driver_data[IWL_FIRST_DRIVER_DATA]) {
+			struct page *page =
+				info->driver_data[IWL_FIRST_DRIVER_DATA];
+			__free_pages(page, 0);
+			info->driver_data[IWL_FIRST_DRIVER_DATA] = NULL;
+		}
+
 		iwl_pcie_txq_free_tfd(trans, txq);
 		q->read_ptr = iwl_queue_inc_wrap(q->read_ptr);
 	}

@@ -1011,11 +1023,20 @@ void iwl_trans_pcie_reclaim(struct iwl_trans *trans, int txq_id, int ssn,
 	for (;
 	     q->read_ptr != tfd_num;
 	     q->read_ptr = iwl_queue_inc_wrap(q->read_ptr)) {
+		struct sk_buff *skb = txq->entries[txq->q.read_ptr].skb;
+		struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 
-		if (WARN_ON_ONCE(txq->entries[txq->q.read_ptr].skb == NULL))
+		if (WARN_ON_ONCE(skb == NULL))
 			continue;
 
-		__skb_queue_tail(skbs, txq->entries[txq->q.read_ptr].skb);

+
+		__skb_queue_tail(skbs, skb);
 
 		txq->entries[txq->q.read_ptr].skb = NULL;
 

@@ -1881,6 +1902,256 @@ static int iwl_fill_data_tbs(struct iwl_trans *trans, struct sk_buff *skb,
 	return 0;
 }