Re: [PATCH v7 4/4] Bluetooth: btqca: inject command complete event during fw download

[Balakrishna Godavarthi <bgodavar@codeaurora.org>]

Hi Marcel,

On 2018-12-31 11:34, Balakrishna Godavarthi wrote:
> Hi Marcel,
> 
> On 2018-12-30 13:40, Marcel Holtmann wrote:
>> Hi Balakrishna,
>> 
>>>>> Latest qualcomm chips are not sending an command complete event for
>>>>> every firmware packet sent to chip. They only respond with a vendor
>>>>> specific event for the last firmware packet. This optimization will
>>>>> decrease the BT ON time. Due to this we are seeing a timeout error
>>>>> message logs on the console during firmware download. Now we are
>>>>> injecting a command complete event once we receive an vendor 
>>>>> specific
>>>>> event for the last RAM firmware packet.
>>>>> Signed-off-by: Balakrishna Godavarthi <bgodavar@codeaurora.org>
>>>>> ---
>>>>> drivers/bluetooth/btqca.c | 39 
>>>>> ++++++++++++++++++++++++++++++++++++++-
>>>>> drivers/bluetooth/btqca.h |  3 +++
>>>>> 2 files changed, 41 insertions(+), 1 deletion(-)
>>>>> diff --git a/drivers/bluetooth/btqca.c b/drivers/bluetooth/btqca.c
>>>>> index ec9e03a6b778..0b533f65f652 100644
>>>>> --- a/drivers/bluetooth/btqca.c
>>>>> +++ b/drivers/bluetooth/btqca.c
>>>>> @@ -144,6 +144,7 @@ static void qca_tlv_check_data(struct 
>>>>> rome_config *config,
>>>>> 		 * In case VSE is skipped, only the last segment is acked.
>>>>> 		 */
>>>>> 		config->dnld_mode = tlv_patch->download_mode;
>>>>> +		config->dnld_type = config->dnld_mode;
>>>>> 		BT_DBG("Total Length           : %d bytes",
>>>>> 		       le32_to_cpu(tlv_patch->total_size));
>>>>> @@ -264,6 +265,31 @@ static int qca_tlv_send_segment(struct hci_dev 
>>>>> *hdev, int seg_size,
>>>>> 	return err;
>>>>> }
>>>>> +static int qca_inject_cmd_complete_event(struct hci_dev *hdev)
>>>>> +{
>>>>> +	struct hci_event_hdr *hdr;
>>>>> +	struct hci_ev_cmd_complete *evt;
>>>>> +	struct sk_buff *skb;
>>>>> +
>>>>> +	skb = bt_skb_alloc(sizeof(*hdr) + sizeof(*evt) + 1, GFP_KERNEL);
>>>>> +	if (!skb)
>>>>> +		return -ENOMEM;
>>>>> +
>>>>> +	hdr = skb_put(skb, sizeof(*hdr));
>>>>> +	hdr->evt = HCI_EV_CMD_COMPLETE;
>>>>> +	hdr->plen = sizeof(*evt) + 1;
>>>>> +
>>>>> +	evt = skb_put(skb, sizeof(*evt));
>>>>> +	evt->ncmd = 1;
>>>>> +	evt->opcode = HCI_OP_NOP;
>>>>> +
>>>>> +	skb_put_u8(skb, QCA_HCI_CC_SUCCESS);
>>>>> +
>>>>> +	hci_skb_pkt_type(skb) = HCI_EVENT_PKT;
>>>>> +
>>>>> +	return hci_recv_frame(hdev, skb);
>>>>> +}
>>>>> +
>>>>> static int qca_download_firmware(struct hci_dev *hdev,
>>>>> 				  struct rome_config *config)
>>>>> {
>>>>> @@ -297,11 +323,22 @@ static int qca_download_firmware(struct 
>>>>> hci_dev *hdev,
>>>>> 		ret = qca_tlv_send_segment(hdev, segsize, segment,
>>>>> 					    config->dnld_mode);
>>>>> 		if (ret)
>>>>> -			break;
>>>>> +			goto out;
>>>>> 		segment += segsize;
>>>>> 	}
>>>>> +	/* Latest qualcomm chipsets are not sending a command complete 
>>>>> event
>>>>> +	 * for every fw packet sent. They only respond with a vendor 
>>>>> specific
>>>>> +	 * event for the last packet. This optimization in the chip will
>>>>> +	 * decrease the BT in initialization time. Here we will inject a 
>>>>> command
>>>>> +	 * complete event to avoid a command timeout error message.
>>>>> +	 */
>>>>> +	if ((config->dnld_type == ROME_SKIP_EVT_VSE_CC ||
>>>>> +	    config->dnld_type == ROME_SKIP_EVT_VSE))
>>>>> +		return qca_inject_cmd_complete_event(hdev);
>>>>> +
>>>> have you actually considered using __hci_cmd_send in that case. It 
>>>> is
>>>> allowed for vendor OGF to use that command. I see you actually do 
>>>> use
>>>> it and now I am failing to understand what this is for.
>>> [Bala]: thanks for reviewing the change.
>>> 
>>> __hci_cmd_send() can be used only to send the command to the chip. it 
>>> will not wait for the response for the command sent.
>>> 
>>> as you know that every vendor command sent to chip will respond with 
>>> vendor specific event and command complete event.
>>> but in our case chip will only respond with vendor specific event 
>>> only. so we are injecting command complete event.
>> 
>> and __hci_cmd_sync_ev is also not working for you? However since you
>> are not waiting for the vendor event anyway and just injecting
>> cmd_complete, I wonder what’s the difference in just using
>> __hci_cmd_send and not bothering to wait or inject at all. I am
>> failing to see where this injection makes a difference.
>> 
>> For me it is a big difference if we are injecting one event like in
>> the case of Intel compared to injecting one for every command. It will
>> show a wrong picture in btmon and that is a bad idea.
>> 
>> Regards
>> 
>> Marcel
> 
> [Bala]: here is the use case, when ever we download the fw packets
> i.e. RAM image, for every command sent(i.e. fw packet) from
> the host chip will respond with an vendor specific event and command
> complete event.
> 
> the above is taking more time to setup the BT device. then we came up
> with solution where we enable flags in fw file (i.e. RAM image header)
> whether to wait for event to be received or sent the total packets and
> wait for the events for the last packet.
> 
> So currently we are handling both the cases in the code. i.e wait for
> event for all packet or wait for an event for the last packet.
> 
> but in the second case i.e. wait for event for the last packet sent,
> we are only receiving an vendor specific event from chip which holds
> the status of fw download.
> 
> so as __hci_cmd_sync_ev() requires an command complete event. so we
> are injecting it after the vendor specific event received for the last
> packet.
> 
> This helps to overcome 0xfc00 timeout error logging on console.

[Bala]: one more point to add
command complete injection is done for only 1 Vendor Specific command 
which is used repeatedly only during firmware download phase
to download firmware chunks. It is not used generically for all Vendor 
Specific commands.

-- 
Regards
Balakrishna.