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

Regards

Marcel

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