From: Vasanth Sadhasivan <vasanth.sadhasivan@xxxxxxxxxxx> commit 62f102c0d1563ff6a31082f5d83b886ad2ff7ca0 upstream. DMA allocated buffers are a precious resource. If there is no need for DMA allocations, then it might be worth to use non-dma allocated buffers. After testing the gs_usb driver with and without DMA allocation, there does not seem to be a significant change in latency or CPU utilization either way. Therefore, DMA allocation is not necessary and removed. Internal buffers used within urbs were managed and freed manually. These buffers are no longer needed to be managed by the driver. The URB_FREE_BUFFER flag, allows for the buffers in question to be automatically freed. Co-developed-by: Rhett Aultman <rhett.aultman@xxxxxxxxxxx> Signed-off-by: Rhett Aultman <rhett.aultman@xxxxxxxxxxx> Signed-off-by: Vasanth Sadhasivan <vasanth.sadhasivan@xxxxxxxxxxx> Link: https://lore.kernel.org/all/20220920154724.861093-2-rhett.aultman@xxxxxxxxxxx Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/net/can/usb/gs_usb.c | 39 ++++++--------------------------------- 1 file changed, 6 insertions(+), 33 deletions(-) --- a/drivers/net/can/usb/gs_usb.c +++ b/drivers/net/can/usb/gs_usb.c @@ -268,8 +268,6 @@ struct gs_can { struct usb_anchor tx_submitted; atomic_t active_tx_urbs; - void *rxbuf[GS_MAX_RX_URBS]; - dma_addr_t rxbuf_dma[GS_MAX_RX_URBS]; }; /* usb interface struct */ @@ -587,9 +585,6 @@ static void gs_usb_xmit_callback(struct if (urb->status) netdev_info(netdev, "usb xmit fail %u\n", txc->echo_id); - - usb_free_coherent(urb->dev, urb->transfer_buffer_length, - urb->transfer_buffer, urb->transfer_dma); } static netdev_tx_t gs_can_start_xmit(struct sk_buff *skb, @@ -618,8 +613,7 @@ static netdev_tx_t gs_can_start_xmit(str if (!urb) goto nomem_urb; - hf = usb_alloc_coherent(dev->udev, dev->hf_size_tx, GFP_ATOMIC, - &urb->transfer_dma); + hf = kmalloc(dev->hf_size_tx, GFP_ATOMIC); if (!hf) { netdev_err(netdev, "No memory left for USB buffer\n"); goto nomem_hf; @@ -663,7 +657,7 @@ static netdev_tx_t gs_can_start_xmit(str hf, dev->hf_size_tx, gs_usb_xmit_callback, txc); - urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP; + urb->transfer_flags |= URB_FREE_BUFFER; usb_anchor_urb(urb, &dev->tx_submitted); can_put_echo_skb(skb, netdev, idx, 0); @@ -678,8 +672,6 @@ static netdev_tx_t gs_can_start_xmit(str gs_free_tx_context(txc); usb_unanchor_urb(urb); - usb_free_coherent(dev->udev, urb->transfer_buffer_length, - urb->transfer_buffer, urb->transfer_dma); if (rc == -ENODEV) { netif_device_detach(netdev); @@ -699,8 +691,7 @@ static netdev_tx_t gs_can_start_xmit(str return NETDEV_TX_OK; badidx: - usb_free_coherent(dev->udev, urb->transfer_buffer_length, - urb->transfer_buffer, urb->transfer_dma); + kfree(hf); nomem_hf: usb_free_urb(urb); @@ -744,7 +735,6 @@ static int gs_can_open(struct net_device for (i = 0; i < GS_MAX_RX_URBS; i++) { struct urb *urb; u8 *buf; - dma_addr_t buf_dma; /* alloc rx urb */ urb = usb_alloc_urb(0, GFP_KERNEL); @@ -752,10 +742,8 @@ static int gs_can_open(struct net_device return -ENOMEM; /* alloc rx buffer */ - buf = usb_alloc_coherent(dev->udev, - dev->parent->hf_size_rx, - GFP_KERNEL, - &buf_dma); + buf = kmalloc(dev->parent->hf_size_rx, + GFP_KERNEL); if (!buf) { netdev_err(netdev, "No memory left for USB buffer\n"); @@ -763,8 +751,6 @@ static int gs_can_open(struct net_device return -ENOMEM; } - urb->transfer_dma = buf_dma; - /* fill, anchor, and submit rx urb */ usb_fill_bulk_urb(urb, dev->udev, @@ -773,7 +759,7 @@ static int gs_can_open(struct net_device buf, dev->parent->hf_size_rx, gs_usb_receive_bulk_callback, parent); - urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP; + urb->transfer_flags |= URB_FREE_BUFFER; usb_anchor_urb(urb, &parent->rx_submitted); @@ -786,17 +772,10 @@ static int gs_can_open(struct net_device "usb_submit failed (err=%d)\n", rc); usb_unanchor_urb(urb); - usb_free_coherent(dev->udev, - sizeof(struct gs_host_frame), - buf, - buf_dma); usb_free_urb(urb); break; } - dev->rxbuf[i] = buf; - dev->rxbuf_dma[i] = buf_dma; - /* Drop reference, * USB core will take care of freeing it */ @@ -854,7 +833,6 @@ static int gs_can_close(struct net_devic int rc; struct gs_can *dev = netdev_priv(netdev); struct gs_usb *parent = dev->parent; - unsigned int i; netif_stop_queue(netdev); @@ -862,11 +840,6 @@ static int gs_can_close(struct net_devic parent->active_channels--; if (!parent->active_channels) { usb_kill_anchored_urbs(&parent->rx_submitted); - for (i = 0; i < GS_MAX_RX_URBS; i++) - usb_free_coherent(dev->udev, - sizeof(struct gs_host_frame), - dev->rxbuf[i], - dev->rxbuf_dma[i]); } /* Stop sending URBs */
