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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.
>>
>
> 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.

Regards

Marcel

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