iwlwifi: pcie: use partial pages if applicable

If we have only 2k RBs like on the latest (AX210) hardware, then
even on x86 where PAGE_SIZE is 4k we currently waste half of the
memory.

If this is the case, return partial pages from the allocator and
track the offset in each RBD (to be able to find the data in them
and remap them later.)

This might also address other platforms with larger PAGE_SIZE by
putting more RBs into a single large page.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

1 files changed, 49 insertions, 10 deletions

diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
index 20f93386fc4d..498a14ebac47 100644
--- a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
+++ b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
@@ -298,6 +298,7 @@ static void iwl_pcie_restock_bd(struct iwl_trans *trans,
 static void iwl_pcie_rxmq_restock(struct iwl_trans *trans,
 				  struct iwl_rxq *rxq)
 {
+	struct iwl_trans_pcie *trans_pcie = IWL_TRANS_GET_PCIE_TRANS(trans);
 	struct iwl_rx_mem_buffer *rxb;
 
 	/*
@@ -318,8 +319,8 @@ static void iwl_pcie_rxmq_restock(struct iwl_trans *trans,
 				       list);
 		list_del(&rxb->list);
 		rxb->invalid = false;
-		/* 12 first bits are expected to be empty */
-		WARN_ON(rxb->page_dma & DMA_BIT_MASK(12));
+		/* some low bits are expected to be unset (depending on hw) */
+		WARN_ON(rxb->page_dma & trans_pcie->supported_dma_mask);
 		/* Point to Rx buffer via next RBD in circular buffer */
 		iwl_pcie_restock_bd(trans, rxq, rxb);
 		rxq->write = (rxq->write + 1) & (rxq->queue_size - 1);
@@ -412,15 +413,34 @@ void iwl_pcie_rxq_restock(struct iwl_trans *trans, struct iwl_rxq *rxq)
  *
  */
 static struct page *iwl_pcie_rx_alloc_page(struct iwl_trans *trans,
-					   gfp_t priority)
+					   u32 *offset, gfp_t priority)
 {
 	struct iwl_trans_pcie *trans_pcie = IWL_TRANS_GET_PCIE_TRANS(trans);
+	unsigned int rbsize = iwl_trans_get_rb_size(trans_pcie->rx_buf_size);
+	unsigned int allocsize = PAGE_SIZE << trans_pcie->rx_page_order;
 	struct page *page;
 	gfp_t gfp_mask = priority;
 
 	if (trans_pcie->rx_page_order > 0)
 		gfp_mask |= __GFP_COMP;
 
+	if (trans_pcie->alloc_page) {
+		spin_lock_bh(&trans_pcie->alloc_page_lock);
+		/* recheck */
+		if (trans_pcie->alloc_page) {
+			*offset = trans_pcie->alloc_page_used;
+			page = trans_pcie->alloc_page;
+			trans_pcie->alloc_page_used += rbsize;
+			if (trans_pcie->alloc_page_used >= allocsize)
+				trans_pcie->alloc_page = NULL;
+			else
+				get_page(page);
+			spin_unlock_bh(&trans_pcie->alloc_page_lock);
+			return page;
+		}
+		spin_unlock_bh(&trans_pcie->alloc_page_lock);
+	}
+
 	/* Alloc a new receive buffer */
 	page = alloc_pages(gfp_mask, trans_pcie->rx_page_order);
 	if (!page) {
@@ -436,6 +456,18 @@ static struct page *iwl_pcie_rx_alloc_page(struct iwl_trans *trans,
 				 "Failed to alloc_pages\n");
 		return NULL;
 	}
+
+	if (2 * rbsize <= allocsize) {
+		spin_lock_bh(&trans_pcie->alloc_page_lock);
+		if (!trans_pcie->alloc_page) {
+			get_page(page);
+			trans_pcie->alloc_page = page;
+			trans_pcie->alloc_page_used = rbsize;
+		}
+		spin_unlock_bh(&trans_pcie->alloc_page_lock);
+	}
+
+	*offset = 0;
 	return page;
 }
 
@@ -456,6 +488,8 @@ void iwl_pcie_rxq_alloc_rbs(struct iwl_trans *trans, gfp_t priority,
 	struct page *page;
 
 	while (1) {
+		unsigned int offset;
+
 		spin_lock(&rxq->lock);
 		if (list_empty(&rxq->rx_used)) {
 			spin_unlock(&rxq->lock);
@@ -463,8 +497,7 @@ void iwl_pcie_rxq_alloc_rbs(struct iwl_trans *trans, gfp_t priority,
 		}
 		spin_unlock(&rxq->lock);
 
-		/* Alloc a new receive buffer */
-		page = iwl_pcie_rx_alloc_page(trans, priority);
+		page = iwl_pcie_rx_alloc_page(trans, &offset, priority);
 		if (!page)
 			return;
 
@@ -482,9 +515,10 @@ void iwl_pcie_rxq_alloc_rbs(struct iwl_trans *trans, gfp_t priority,
 
 		BUG_ON(rxb->page);
 		rxb->page = page;
+		rxb->offset = offset;
 		/* Get physical address of the RB */
 		rxb->page_dma =
-			dma_map_page(trans->dev, page, 0,
+			dma_map_page(trans->dev, page, rxb->offset,
 				     trans_pcie->rx_buf_bytes,
 				     DMA_FROM_DEVICE);
 		if (dma_mapping_error(trans->dev, rxb->page_dma)) {
@@ -567,13 +601,15 @@ static void iwl_pcie_rx_allocator(struct iwl_trans *trans)
 			BUG_ON(rxb->page);
 
 			/* Alloc a new receive buffer */
-			page = iwl_pcie_rx_alloc_page(trans, gfp_mask);
+			page = iwl_pcie_rx_alloc_page(trans, &rxb->offset,
+						      gfp_mask);
 			if (!page)
 				continue;
 			rxb->page = page;
 
 			/* Get physical address of the RB */
-			rxb->page_dma = dma_map_page(trans->dev, page, 0,
+			rxb->page_dma = dma_map_page(trans->dev, page,
+						     rxb->offset,
 						     trans_pcie->rx_buf_bytes,
 						     DMA_FROM_DEVICE);
 			if (dma_mapping_error(trans->dev, rxb->page_dma)) {
@@ -1190,6 +1226,9 @@ void iwl_pcie_rx_free(struct iwl_trans *trans)
 	kfree(trans_pcie->rx_pool);
 	kfree(trans_pcie->global_table);
 	kfree(trans_pcie->rxq);
+
+	if (trans_pcie->alloc_page)
+		__free_pages(trans_pcie->alloc_page, trans_pcie->rx_page_order);
 }
 
 static void iwl_pcie_rx_move_to_allocator(struct iwl_rxq *rxq,
@@ -1261,7 +1300,7 @@ static void iwl_pcie_rx_handle_rb(struct iwl_trans *trans,
 		bool reclaim;
 		int index, cmd_index, len;
 		struct iwl_rx_cmd_buffer rxcb = {
-			._offset = offset,
+			._offset = rxb->offset + offset,
 			._rx_page_order = trans_pcie->rx_page_order,
 			._page = rxb->page,
 			._page_stolen = false,
@@ -1367,7 +1406,7 @@ static void iwl_pcie_rx_handle_rb(struct iwl_trans *trans,
 	 * rx_free list for reuse later. */
 	if (rxb->page != NULL) {
 		rxb->page_dma =
-			dma_map_page(trans->dev, rxb->page, 0,
+			dma_map_page(trans->dev, rxb->page, rxb->offset,
 				     trans_pcie->rx_buf_bytes,
 				     DMA_FROM_DEVICE);
 		if (dma_mapping_error(trans->dev, rxb->page_dma)) {