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

Sean Wang
2018-08-03T13:42:29Z

On Fri, 2018-08-03 at 14:51 +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);
> >>
> >> actually the command also needs to better go via the raw_q anyway since it doesn’t come back with the cmd status or cmd complete. You have it waiting for a vendor event. Maybe with is something we need to consider with __hci_cmd_sync_ev anyway.
> >>
> >> Johan would know best since he wrote that code. Anyway, we should fix that in the core and not have you hack around it.
> >>
> >
> > yes, my case is that received event is neither cmd status nor cmd complete. It is completely a vendor event.
> >
> > if it wants to be solved by the core layer, do you permit that I remove the hack and then send it in the next version?
>
> we need to have a __hci_raw_sync_ev that uses the hdev->raw_q and waits for the specified event to come back. I never realized that you are missing the cmd status or cmd complete. So this is similar to the original CSR vendor commands which had the same behavior.
>
> I have the feeling that you hdev->cmd_cnt increment is just hiding the problem here. If you really think that it is not chains any side effects we can merge the driver with a big warning and fix this up. However the clean way would be for you to create a patch that introduces __hci_raw_sync_ev as describe above.

What do you think of this? If I add extra atomic_set 1 on cmd_cnt after driver really got a vendor event back instead of blinding to increment for every packet sent.

the behavior is the same to receive a cmd status or complete. it should not have side effects.

96 skb = __hci_cmd_sync_ev(hdev, 0xfc6f, hlen, &wc, HCI_VENDOR_PKT,
97 HCI_INIT_TIMEOUT);
98
99 if (IS_ERR(skb)) {
100 int err = PTR_ERR(skb);
101
102 bt_dev_err(hdev, "Failed to send wmt cmd (%d)", err);
103 return err;
104 }
105
106 if (!test_bit(HCI_RESET, &hdev->flags)) <<<<<<
107 atomic_set(&hdev->cmd_cnt, 1); <<<<<<
108
109 kfree_skb(skb);

> Regards
>
> Marcel
>