| From: Felix Fietkau <nbd@nbd.name> |
| Date: Thu, 27 Aug 2020 06:32:03 +0200 |
| Subject: [PATCH] net: ethernet: mtk_eth_soc: cache hardware pointer of last |
| freed tx descriptor |
| |
| The value is only updated by the CPU, so it is cheaper to access from the ring |
| data structure than from a hardware register |
| |
| Signed-off-by: Felix Fietkau <nbd@nbd.name> |
| --- |
| |
| --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c |
| +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c |
| @@ -1393,7 +1393,7 @@ static int mtk_poll_tx_qdma(struct mtk_e |
| struct mtk_tx_buf *tx_buf; |
| u32 cpu, dma; |
| |
| - cpu = mtk_r32(eth, MTK_QTX_CRX_PTR); |
| + cpu = ring->last_free_ptr; |
| dma = mtk_r32(eth, MTK_QTX_DRX_PTR); |
| |
| desc = mtk_qdma_phys_to_virt(ring, cpu); |
| @@ -1427,6 +1427,7 @@ static int mtk_poll_tx_qdma(struct mtk_e |
| cpu = next_cpu; |
| } |
| |
| + ring->last_free_ptr = cpu; |
| mtk_w32(eth, cpu, MTK_QTX_CRX_PTR); |
| |
| return budget; |
| @@ -1627,6 +1628,7 @@ static int mtk_tx_alloc(struct mtk_eth * |
| atomic_set(&ring->free_count, MTK_DMA_SIZE - 2); |
| ring->next_free = &ring->dma[0]; |
| ring->last_free = &ring->dma[MTK_DMA_SIZE - 1]; |
| + ring->last_free_ptr = (u32)(ring->phys + ((MTK_DMA_SIZE - 1) * sz)); |
| ring->thresh = MAX_SKB_FRAGS; |
| |
| /* make sure that all changes to the dma ring are flushed before we |
| @@ -1640,9 +1642,7 @@ static int mtk_tx_alloc(struct mtk_eth * |
| mtk_w32(eth, |
| ring->phys + ((MTK_DMA_SIZE - 1) * sz), |
| MTK_QTX_CRX_PTR); |
| - mtk_w32(eth, |
| - ring->phys + ((MTK_DMA_SIZE - 1) * sz), |
| - MTK_QTX_DRX_PTR); |
| + mtk_w32(eth, ring->last_free_ptr, MTK_QTX_DRX_PTR); |
| mtk_w32(eth, (QDMA_RES_THRES << 8) | QDMA_RES_THRES, |
| MTK_QTX_CFG(0)); |
| } else { |
| --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.h |
| +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.h |
| @@ -644,6 +644,7 @@ struct mtk_tx_buf { |
| * @phys: The physical addr of tx_buf |
| * @next_free: Pointer to the next free descriptor |
| * @last_free: Pointer to the last free descriptor |
| + * @last_free_ptr: Hardware pointer value of the last free descriptor |
| * @thresh: The threshold of minimum amount of free descriptors |
| * @free_count: QDMA uses a linked list. Track how many free descriptors |
| * are present |
| @@ -654,6 +655,7 @@ struct mtk_tx_ring { |
| dma_addr_t phys; |
| struct mtk_tx_dma *next_free; |
| struct mtk_tx_dma *last_free; |
| + u32 last_free_ptr; |
| u16 thresh; |
| atomic_t free_count; |
| int dma_size; |