Re: [PATCH v7 2/3] Bluetooth: mediatek: Add protocol support for MediaTek serial devices

Sean Wang
2018-08-02T08:48:40Z

On Thu, 2018-08-02 at 09:38 +0200, Marcel Holtmann wrote:
> Hi Sean,
>

[ ... ]

> >>> +
> >>> +static int mtk_hci_wmt_sync(struct hci_dev *hdev, u8 op, u8 flag, u16 plen,
> >>> + const void *param)
> >>> +{
> >>> + struct mtk_hci_wmt_cmd wc;
> >>> + struct mtk_wmt_hdr *hdr;
> >>> + struct sk_buff *skb;
> >>> + u32 hlen;
> >>> +
> >>> + hlen = sizeof(*hdr) + plen;
> >>> + if (hlen > 255)
> >>> + return -EINVAL;
> >>> +
> >>> + hdr = (struct mtk_wmt_hdr *)&wc;
> >>> + hdr->dir = 1;
> >>> + hdr->op = op;
> >>> + hdr->dlen = cpu_to_le16(plen + 1);
> >>> + hdr->flag = flag;
> >>> + memcpy(wc.data, param, plen);
> >>> +
> >>> + atomic_inc(&hdev->cmd_cnt);
> >>
> >> Why are you doing this one. It will need a comment here if really needed. However I doubt that this is needed. You are only using it from hdev->setup and hdev->shutdown callbacks.
> >>
> >
> > An increment on cmd_cnt is really needed because hci_cmd_work would check whether cmd_cnt is positive and then has a decrement on cmd_cnt before a packet is being sent out.
> >
> > okay will add a comment.
>
> but you are in ->setup callback this time. So if you need this, then all the other ->setup routines would actually fail as well. Either this is leftover from when you did things in ->probe or ->open or this is some thing we might better fix properly in the core instead of papering over it. Can you recheck if this is really needed.
>

I added a counter print and the counter increments as below

/* atomic_inc(&hdev->cmd_cnt); */
pr_info("cmd_cnt = %d\n" , atomic_read(&hdev->cmd_cnt));

skb = __hci_cmd_sync_ev(hdev, 0xfc6f, hlen, &wc, HCI_VENDOR_PKT,
HCI_INIT_TIMEOUT);

and the log show up that

[ 334.049156] Bluetooth: hci0: command 0xfc6f tx timeout
[ 334.054840] cmd_cnt = 0
[ 336.065076] Bluetooth: hci0: command 0xfc6f tx timeout
[ 336.070795] cmd_cnt = 0
[ 338.080997] Bluetooth: hci0: command 0xfc6f tx timeout
[ 338.086683] cmd_cnt = 0
[ 340.096907] Bluetooth: hci0: command 0xfc6f tx timeout
[ 340.102609] cmd_cnt = 0
[ 342.112824] Bluetooth: hci0: command 0xfc6f tx timeout
[ 342.118520] cmd_cnt = 0
[ 344.128747] Bluetooth: hci0: command 0xfc6f tx timeout
[ 344.134454] cmd_cnt = 0
[ 346.144667] Bluetooth: hci0: command 0xfc6f tx timeout
[ 346.150372] cmd_cnt = 0

The packet is dropped by hci_cmd_work at [1], so I also wondered why the
other vendor driver works, it seems the counter needs to be incremented
before every skb is being queued to cmd_q.

4257 static void hci_cmd_work(struct work_struct *work)
4258 {
4259 struct hci_dev *hdev = container_of(work, struct hci_dev, cmd_work);
4260 struct sk_buff *skb;
4261
4262 BT_DBG("%s cmd_cnt %d cmd queued %d", hdev->name,
4263 atomic_read(&hdev->cmd_cnt), skb_queue_len(&hdev->cmd_q));
4264
4265 /* Send queued commands */

[1]
4266 if (atomic_read(&hdev->cmd_cnt)) { /* dropped when cmd_cnt is zero */
4267 skb = skb_dequeue(&hdev->cmd_q);
4268 if (!skb)
4269 return;
4270
4271 kfree_skb(hdev->sent_cmd);
4272
4273 hdev->sent_cmd = skb_clone(skb, GFP_KERNEL);
4274 if (hdev->sent_cmd) {
4275 atomic_dec(&hdev->cmd_cnt); /* cmd_cnt-- */
4276 hci_send_frame(hdev, skb);

> >>> +
> >>> + skb = __hci_cmd_sync_ev(hdev, 0xfc6f, hlen, &wc, HCI_VENDOR_PKT,
> >>> + HCI_INIT_TIMEOUT);
> >>> +
> >>> + if (IS_ERR(skb)) {
> >>> + int err = PTR_ERR(skb);
> >>> +
> >>> + bt_dev_err(hdev, "Failed to send wmt cmd (%d)", err);
> >>> + return err;
> >>> + }
> >>> +
> >>> + kfree_skb(skb);
> >>> +
> >>> + return 0;
> >>> +}
> >>> +

[ ... ]

> >>> + shdr->dlen2 = dlen & 0xff;
> >>> + shdr->cs = p[0] + p[1] + p[2];
> >>
> >
> > as above discussion about shr->cs , it can be filled with zero to have less computing
>
> If it has no value, then zero it out and add a comment for it.
>

okay

> >
> >> I would add another comment here that this added the STP trailer. And change the above to mention it adds the STP header.
> >>
> >
> > sure
> >
> >> And you might want to check if there is space for the trailer as well. Otherwise skb_put tends to call BUG() if I remember correctly. I know this is super unlikely since our bt_skb_alloc is pretty large.
> >>
> >
> > sure, I will add the handling for that. it should be better to make sure all rooms are enough for header and trailer before adding content to them
> >
> >

[ ... ]

> >> You want to add a MODULE_FIRMWARE here as well.
> >>
> >
> > okay
>
> Regards
>
> Marcel
>