This is a note to let you know that I've just added the patch titled
can: gs_usb: remove dma allocations
to the 6.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
can-gs_usb-remove-dma-allocations.patch
and it can be found in the queue-6.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 62f102c0d1563ff6a31082f5d83b886ad2ff7ca0 Mon Sep 17 00:00:00 2001
From: Vasanth Sadhasivan <vasanth.sadhasivan@xxxxxxxxxxx>
Date: Tue, 20 Sep 2022 11:47:24 -0400
Subject: can: gs_usb: remove dma allocations
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 */
Patches currently in stable-queue which might be from vasanth.sadhasivan@xxxxxxxxxxx are
queue-6.0/can-gs_usb-remove-dma-allocations.patch
