[...]
> In usb_sg_init() urb->num_sgs is set 0 for sg_tablesize = 0 controllers.
> In mt76 we set urb->num_sgs to 1. I thought it is fine, but now I think
> this is bug. We can fix that without changing allocation method and
> still use SG allocation. Attached patch do this, please check if it works
> on rpi. Patch is on top of your error path fixes.
>
> Stanislaw
> From f79ac0df967d406523d0a1c03a138d1394e7665a Mon Sep 17 00:00:00 2001
> From: Stanislaw Gruszka <sgrus...@redhat.com>
> Date: Tue, 12 Feb 2019 10:02:53 +0100
> Subject: [PATCH] mt76usb: do not set urb->num_sgs to 1 for non SG usb host
> drivers
>
> Track number of segments in mt76u_buf structure and do not
> submit urbs with urb->num_sgs = 1 if usb host driver
> sg_tablesize is zero.
>
> This suppose fix problem of mt76 not working with some usb
> host controllers like dwc2.
>
> Signed-off-by: Stanislaw Gruszka <sgrus...@redhat.com>
> ---
> drivers/net/wireless/mediatek/mt76/mt76.h | 1 +
> drivers/net/wireless/mediatek/mt76/usb.c | 55 ++++++++++++++---------
> 2 files changed, 36 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/net/wireless/mediatek/mt76/mt76.h
> b/drivers/net/wireless/mediatek/mt76/mt76.h
> index 2e5bcb3fdff7..eadc913c37b6 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt76.h
> +++ b/drivers/net/wireless/mediatek/mt76/mt76.h
> @@ -86,6 +86,7 @@ struct mt76_queue_buf {
> struct mt76u_buf {
> struct mt76_dev *dev;
> struct urb *urb;
> + int num_sgs;
> size_t len;
> bool done;
> };
> diff --git a/drivers/net/wireless/mediatek/mt76/usb.c
> b/drivers/net/wireless/mediatek/mt76/usb.c
> index a1811c39415e..d82de59ec6dc 100644
> --- a/drivers/net/wireless/mediatek/mt76/usb.c
> +++ b/drivers/net/wireless/mediatek/mt76/usb.c
> @@ -299,14 +299,14 @@ mt76u_fill_rx_sg(struct mt76_dev *dev, struct mt76u_buf
> *buf,
> if (i < nsgs) {
> int j;
>
> - for (j = nsgs; j < urb->num_sgs; j++)
> + for (j = nsgs; j < buf->num_sgs; j++)
> skb_free_frag(sg_virt(&urb->sg[j]));
> - urb->num_sgs = i;
> + buf->num_sgs = i;
> }
>
> - urb->num_sgs = max_t(int, i, urb->num_sgs);
> - buf->len = urb->num_sgs * sglen,
> - sg_init_marker(urb->sg, urb->num_sgs);
> + buf->num_sgs = max_t(int, i, buf->num_sgs);
> + buf->len = buf->num_sgs * sglen,
> + sg_init_marker(urb->sg, buf->num_sgs);
>
> return i ? : -ENOMEM;
> }
> @@ -325,6 +325,7 @@ int mt76u_buf_alloc(struct mt76_dev *dev, struct
> mt76u_buf *buf,
>
> sg_init_table(buf->urb->sg, nsgs);
> buf->dev = dev;
> + buf->num_sgs = nsgs;
>
> return mt76u_fill_rx_sg(dev, buf, nsgs, len, sglen);
> }
> @@ -336,7 +337,7 @@ void mt76u_buf_free(struct mt76u_buf *buf)
> struct scatterlist *sg;
> int i;
>
> - for (i = 0; i < urb->num_sgs; i++) {
> + for (i = 0; i < buf->num_sgs; i++) {
> sg = &urb->sg[i];
> if (!sg)
> continue;
> @@ -347,9 +348,10 @@ void mt76u_buf_free(struct mt76u_buf *buf)
> }
> EXPORT_SYMBOL_GPL(mt76u_buf_free);
>
> -int mt76u_submit_buf(struct mt76_dev *dev, int dir, int index,
> - struct mt76u_buf *buf, gfp_t gfp,
> - usb_complete_t complete_fn, void *context)
> +static void
> +mt76u_fill_bulk_urb(struct mt76_dev *dev, int dir, int index,
> + struct mt76u_buf *buf, usb_complete_t complete_fn,
> + void *context)
> {
> struct usb_interface *intf = to_usb_interface(dev->dev);
> struct usb_device *udev = interface_to_usbdev(intf);
> @@ -360,9 +362,25 @@ int mt76u_submit_buf(struct mt76_dev *dev, int dir, int
> index,
> else
> pipe = usb_sndbulkpipe(udev, dev->usb.out_ep[index]);
>
> - usb_fill_bulk_urb(buf->urb, udev, pipe, NULL, buf->len,
> - complete_fn, context);
> + usb_fill_bulk_urb(buf->urb, udev, pipe, NULL, buf->len, complete_fn,
> + context);
> +
> + if (udev->bus->sg_tablesize > 0) {
> + buf->urb->num_sgs = buf->num_sgs;
> + } else {
> + WARN_ON_ONCE(buf->num_sgs != 1);
> + /* See usb_sg_init() */
> + buf->urb->num_sgs = 0;
> + if (!PageHighMem(sg_page(buf->urb->sg)))
> + buf->urb->transfer_buffer = sg_virt(buf->urb->sg);
please correct me if I am wrong but doing so we will use transfer_buffer
for 95% of the use cases, right? If so why not keep it simple and always
use it when sg_tablesize is 0 (avoiding SG I/O)?
Btw this is what I proposed with the RFC series actually :) (always use
transfer_buffer in the usb 2.0 case)
Regards,
Lorenzo
> + }
> +}
>
> +int mt76u_submit_buf(struct mt76_dev *dev, int dir, int index,
> + struct mt76u_buf *buf, gfp_t gfp,
> + usb_complete_t complete_fn, void *context)
> +{
> + mt76u_fill_bulk_urb(dev, dir, index, buf, complete_fn, context);
> return usb_submit_urb(buf->urb, gfp);
> }
> EXPORT_SYMBOL_GPL(mt76u_submit_buf);
> @@ -672,10 +690,11 @@ static void mt76u_complete_tx(struct urb *urb)
> }
>
> static int
> -mt76u_tx_build_sg(struct sk_buff *skb, struct urb *urb)
> +mt76u_tx_build_sg(struct sk_buff *skb, struct mt76u_buf *buf)
> {
> int nsgs = 1 + skb_shinfo(skb)->nr_frags;
> struct sk_buff *iter;
> + struct urb *urb = buf->urb;
>
> skb_walk_frags(skb, iter)
> nsgs += 1 + skb_shinfo(iter)->nr_frags;
> @@ -684,7 +703,8 @@ mt76u_tx_build_sg(struct sk_buff *skb, struct urb *urb)
>
> nsgs = min_t(int, MT_SG_MAX_SIZE, nsgs);
> sg_init_marker(urb->sg, nsgs);
> - urb->num_sgs = nsgs;
> + buf->num_sgs = nsgs;
> + buf->len = skb->len;
>
> return skb_to_sgvec_nomark(skb, urb->sg, 0, skb->len);
> }
> @@ -694,12 +714,9 @@ mt76u_tx_queue_skb(struct mt76_dev *dev, struct
> mt76_queue *q,
> struct sk_buff *skb, struct mt76_wcid *wcid,
> struct ieee80211_sta *sta)
> {
> - struct usb_interface *intf = to_usb_interface(dev->dev);
> - struct usb_device *udev = interface_to_usbdev(intf);
> u8 ep = q2ep(q->hw_idx);
> struct mt76u_buf *buf;
> u16 idx = q->tail;
> - unsigned int pipe;
> int err;
>
> if (q->queued == q->ndesc)
> @@ -712,13 +729,11 @@ mt76u_tx_queue_skb(struct mt76_dev *dev, struct
> mt76_queue *q,
> buf = &q->entry[idx].ubuf;
> buf->done = false;
>
> - err = mt76u_tx_build_sg(skb, buf->urb);
> + err = mt76u_tx_build_sg(skb, buf);
> if (err < 0)
> return err;
>
> - pipe = usb_sndbulkpipe(udev, dev->usb.out_ep[ep]);
> - usb_fill_bulk_urb(buf->urb, udev, pipe, NULL, skb->len,
> - mt76u_complete_tx, buf);
> + mt76u_fill_bulk_urb(dev, USB_DIR_OUT, ep, buf, mt76u_complete_tx, buf);
>
> q->tail = (q->tail + 1) % q->ndesc;
> q->entry[idx].skb = skb;
> --
> 2.19.2
>
