Date:   Wed, 20 Feb 2019 14:22:08 +0100
From:   Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
To:     Stanislaw Gruszka <sgruszka@redhat.com>
Cc:     Felix Fietkau <nbd@nbd.name>,
        Stefan Wahren <stefan.wahren@i2se.com>,
        Alan Stern <stern@rowland.harvard.edu>,
        Doug Anderson <dianders@chromium.org>,
        Minas Harutyunyan <hminas@synopsys.com>,
        USB list <linux-usb@vger.kernel.org>,
        linux-wireless <linux-wireless@vger.kernel.org>
Subject: Re: [BUG] mt76x0u: Probing issues on Raspberry Pi 3 B+
Message-ID: <20190220132206.GF2626@localhost.localdomain>
References: <1411983628.668277.1550315118443@email.ionos.de>
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 <0e29e99a-6ed4-40fe-1f38-30f1b5530a16@nbd.name>
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 <a035966b-99f8-1109-d96f-0c3862d26518@nbd.name>
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> On Tue, Feb 19, 2019 at 01:19:26PM +0100, Felix Fietkau wrote:
> > >> >> The way I see it, we have two choices.
> > >> >> 1. Fix dwc2 to do its alignment quirk for the urb->sg != NULL case
> > >> >> 2. Rely on urb->transfer_buffer and keep urb->sg NULL
> > >> > 
> > >> > I agree, if this is only needed for dwc2. Though I would investigate
> > >> > if this is not a bug on other platforms as well.
> > >> >From what I can see, using Lorenzo's patches seems to be the better
> > >> solution, since they avoid these corner cases in dwc2 (and maybe other
> > >> drivers as well). I will apply them and then we'll see if we need to do
> > >> any further improvements later on.
> > > 
> > > They work on rpi dwc2, but they do not address root of the problem.
> > > There is clearly something wrong how mt76usb handle SG, what is not
> > > fixed. And adding disable_usb_sg module parameter for hcd's supporting
> > > SG should be red flag.
> > I think we're simply dealing with multiple issues here, only some of
> > which are fixed by Lorenzo's patches.
> > I'm pretty sure it's still wrong for mt76 to try to align its buffers,
> > since the Linux USB API supports non-aligned transfer buffers and it
> > should be up to the controller driver to deal with that.
> 
> Agree.
> 
> > dwc2 tries to do that, but that has limitations which I already pointed
> > out and which are properly dealt with by Lorenzo's patches.
> 
> I planed to just accept current solution, but I started to work on patch
> that remove len, sglen arguments from mt76u_buf_alloc() and use
> q->buf_size and SKB_WITH_OVERHEAD(q->buf_size) directly and realized how
> related code is now tangled.
> 
> Would be ok to send this patch with proper changelog as fix for RPI
> against wireless-drivers and cc:stable (assuming it works and really
> fix things on RPI) and revert Lorenzo's patches in -next ?

Hi Stanislaw,

what is the advantage of doing so? You have duplicated most of the fields that are
already in the urb data structure and you use transfer_buffer (no SG I/O).
Moreover I have ready a series that removes 99% of the dual allocation code and
maintain it in the control path (instead of the datapath one).
I need just to rebase it ontop of your series. I will post it soon.

Regards,
Lorenzo

> 
> Stanislaw
> 
> From 4f8d7d3f4031b0a97b3bb147cb7e52533886e7cc Mon Sep 17 00:00:00 2001
> From: Stanislaw Gruszka <sgruszka@redhat.com>
> Date: Wed, 20 Feb 2019 13:29:42 +0100
> Subject: [PATCH] mt76usb: use urb transfer_buffer for one segment
> 
> Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
> ---
>  drivers/net/wireless/mediatek/mt76/mt76.h     |  2 +
>  .../wireless/mediatek/mt76/mt76x02_usb_mcu.c  |  4 +-
>  drivers/net/wireless/mediatek/mt76/usb.c      | 75 +++++++++++--------
>  3 files changed, 46 insertions(+), 35 deletions(-)
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/mt76.h b/drivers/net/wireless/mediatek/mt76/mt76.h
> index 2e5bcb3fdff7..7e0680daeee6 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt76.h
> +++ b/drivers/net/wireless/mediatek/mt76/mt76.h
> @@ -86,6 +86,8 @@ struct mt76_queue_buf {
>  struct mt76u_buf {
>  	struct mt76_dev *dev;
>  	struct urb *urb;
> +	struct scatterlist *sg;
> +	int num_sgs;
>  	size_t len;
>  	bool done;
>  };
> diff --git a/drivers/net/wireless/mediatek/mt76/mt76x02_usb_mcu.c b/drivers/net/wireless/mediatek/mt76/mt76x02_usb_mcu.c
> index da299b8a1334..75561910d630 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt76x02_usb_mcu.c
> +++ b/drivers/net/wireless/mediatek/mt76/mt76x02_usb_mcu.c
> @@ -90,7 +90,7 @@ static int mt76x02u_mcu_wait_resp(struct mt76_dev *dev, u8 seq)
>  		if (urb->status)
>  			return -EIO;
>  
> -		data = sg_virt(&urb->sg[0]);
> +		data = sg_virt(&buf->sg[0]);
>  		if (usb->mcu.rp)
>  			mt76x02u_multiple_mcu_reads(dev, data + 4,
>  						    urb->actual_length - 8);
> @@ -266,7 +266,7 @@ static int
>  __mt76x02u_mcu_fw_send_data(struct mt76x02_dev *dev, struct mt76u_buf *buf,
>  			    const void *fw_data, int len, u32 dst_addr)
>  {
> -	u8 *data = sg_virt(&buf->urb->sg[0]);
> +	u8 *data = sg_virt(&buf->sg[0]);
>  	DECLARE_COMPLETION_ONSTACK(cmpl);
>  	__le32 info;
>  	u32 val;
> diff --git a/drivers/net/wireless/mediatek/mt76/usb.c b/drivers/net/wireless/mediatek/mt76/usb.c
> index a1811c39415e..57bb16eaff06 100644
> --- a/drivers/net/wireless/mediatek/mt76/usb.c
> +++ b/drivers/net/wireless/mediatek/mt76/usb.c
> @@ -277,7 +277,6 @@ mt76u_fill_rx_sg(struct mt76_dev *dev, struct mt76u_buf *buf,
>  		 int nsgs, int len, int sglen)
>  {
>  	struct mt76_queue *q = &dev->q_rx[MT_RXQ_MAIN];
> -	struct urb *urb = buf->urb;
>  	int i;
>  
>  	spin_lock_bh(&q->rx_page_lock);
> @@ -292,21 +291,21 @@ mt76u_fill_rx_sg(struct mt76_dev *dev, struct mt76u_buf *buf,
>  
>  		page = virt_to_head_page(data);
>  		offset = data - page_address(page);
> -		sg_set_page(&urb->sg[i], page, sglen, offset);
> +		sg_set_page(&buf->sg[i], page, sglen, offset);
>  	}
>  	spin_unlock_bh(&q->rx_page_lock);
>  
>  	if (i < nsgs) {
>  		int j;
>  
> -		for (j = nsgs; j < urb->num_sgs; j++)
> -			skb_free_frag(sg_virt(&urb->sg[j]));
> -		urb->num_sgs = i;
> +		for (j = nsgs; j < buf->num_sgs; j++)
> +			skb_free_frag(sg_virt(&buf->sg[j]));
> +		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(buf->sg, buf->num_sgs);
>  
>  	return i ? : -ENOMEM;
>  }
> @@ -318,13 +317,14 @@ int mt76u_buf_alloc(struct mt76_dev *dev, struct mt76u_buf *buf,
>  	if (!buf->urb)
>  		return -ENOMEM;
>  
> -	buf->urb->sg = devm_kcalloc(dev->dev, nsgs, sizeof(*buf->urb->sg),
> +	buf->sg = devm_kcalloc(dev->dev, nsgs, sizeof(*buf->sg),
>  				    gfp);
> -	if (!buf->urb->sg)
> +	if (!buf->sg)
>  		return -ENOMEM;
>  
> -	sg_init_table(buf->urb->sg, nsgs);
> +	sg_init_table(buf->sg, nsgs);
>  	buf->dev = dev;
> +	buf->num_sgs = nsgs;
>  
>  	return mt76u_fill_rx_sg(dev, buf, nsgs, len, sglen);
>  }
> @@ -332,12 +332,11 @@ EXPORT_SYMBOL_GPL(mt76u_buf_alloc);
>  
>  void mt76u_buf_free(struct mt76u_buf *buf)
>  {
> -	struct urb *urb = buf->urb;
>  	struct scatterlist *sg;
>  	int i;
>  
> -	for (i = 0; i < urb->num_sgs; i++) {
> -		sg = &urb->sg[i];
> +	for (i = 0; i < buf->num_sgs; i++) {
> +		sg = &buf->sg[i];
>  		if (!sg)
>  			continue;
>  
> @@ -347,9 +346,10 @@ 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 +360,22 @@ 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 (buf->num_sgs > 1) {
> +		buf->urb->num_sgs = buf->num_sgs;
> +		buf->urb->sg = buf->sg;
> +	} else {
> +		buf->urb->transfer_buffer = sg_virt(buf->sg);
> +	}
> +}
>  
> +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);
> @@ -672,7 +685,7 @@ 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;
> @@ -680,13 +693,14 @@ mt76u_tx_build_sg(struct sk_buff *skb, struct urb *urb)
>  	skb_walk_frags(skb, iter)
>  		nsgs += 1 + skb_shinfo(iter)->nr_frags;
>  
> -	memset(urb->sg, 0, sizeof(*urb->sg) * MT_SG_MAX_SIZE);
> +	memset(buf->sg, 0, sizeof(*buf->sg) * MT_SG_MAX_SIZE);
>  
>  	nsgs = min_t(int, MT_SG_MAX_SIZE, nsgs);
> -	sg_init_marker(urb->sg, nsgs);
> -	urb->num_sgs = nsgs;
> +	sg_init_marker(buf->sg, nsgs);
> +	buf->num_sgs = nsgs;
> +	buf->len = skb->len;
>  
> -	return skb_to_sgvec_nomark(skb, urb->sg, 0, skb->len);
> +	return skb_to_sgvec_nomark(skb, buf->sg, 0, skb->len);
>  }
>  
>  static int
> @@ -694,12 +708,9 @@ 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 +723,11 @@ 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;
> @@ -776,8 +785,8 @@ static int mt76u_alloc_tx(struct mt76_dev *dev)
>  			if (!buf->urb)
>  				return -ENOMEM;
>  
> -			buf->urb->sg = devm_kzalloc(dev->dev, size, GFP_KERNEL);
> -			if (!buf->urb->sg)
> +			buf->sg = devm_kzalloc(dev->dev, size, GFP_KERNEL);
> +			if (!buf->sg)
>  				return -ENOMEM;
>  		}
>  	}
> -- 
> 2.20.1
>