Message-ID: <20190110204328.GA261387@google.com>
Date:   Thu, 10 Jan 2019 12:43:28 -0800
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Balakrishna Godavarthi <bgodavar@...eaurora.org>
Cc:     Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        linux-kernel@...r.kernel.org, linux-bluetooth@...r.kernel.org,
        hemantg@...eaurora.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v7 4/4] Bluetooth: btqca: inject command complete event
 during fw download

Hi Balakrishna,

On Thu, Jan 10, 2019 at 08:30:43PM +0530, Balakrishna Godavarthi wrote:
> Hi Matthias,
> 
> On 2019-01-03 03:45, Matthias Kaehlcke wrote:
> > On Mon, Dec 31, 2018 at 11:34:46AM +0530, 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@...eaurora.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;
> > 
> > After looking a bit more at it I realize HCI_OP_NOP is not a good
> > value in this case:
> > 
> > static void hci_cmd_complete_evt(...)
> > {
> >   ...
> > 
> >   if (*opcode != HCI_OP_NOP)
> >     cancel_delayed_work(&hdev->cmd_timer);
> > 
> >   ...
> > }
> > 
> > https://elixir.bootlin.com/linux/v4.19/source/net/bluetooth/hci_event.c#L3351
> > 
> > Cancelling the command timeout is precisely what we want. Not sure why
> > the patch with HCI_OP_NOP makes the timeouts go away in most cases
> > (but not e.g. when inserting an msleep(1000) after downloading the
> > NVM.
> > 
> > I suggest to pass the opcode of the command to be completed.
> > 
> > > > > > > +
> > > > > > > +	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.
> > 
> > Some more details:
> > 
> > The timeout error is actually from reading the 'SoC version', which
> > uses the same command code as the firmware download
> > (EDL_PATCH_CMD_OPCODE). Without reading the 'SoC version' it would be
> > from the command to write the first firmware segment.
> > 
> > If the download of a firmware binary takes >= 2s (HCI_CMD_TIMEOUT) the
> > timeout would still occur. If necessary this could be mitigated by
> > injecting some command complete events during the firmware download,
> > though I expect Marcel wouldn't be overly happy with that, since it
> > would affect btmon even more.
> > 
> > Regards
> > 
> > Matthias
> 
> [Bala]: Basically every vendor specific command we sent to chip,
> chip should respond with an vendor specific event followed by an command
> complete event
> or some times it will only respond with an command complete event.
> but in any case command complete event is mandatory to all the command we
> sent to the chip.

Is this ("command complete event is mandatory to all the command we
sent to the chip") a description of what the chip actually does, or
what it should be doing according to the spec?

As mentioned earlier, the timeout we see originates from reading the
SoC version:

diff --git a/drivers/bluetooth/btqca.c b/drivers/bluetooth/btqca.c
index 0b533f65f652fc..1e484e61799571 100644
--- a/drivers/bluetooth/btqca.c
+++ b/drivers/bluetooth/btqca.c
@@ -400,6 +400,10 @@ int qca_uart_setup(struct hci_dev *hdev, uint8_t baudrate,
                return err;
        }

+       printk("DBG: ZZZzzzzzzz\n");
+       msleep(2500);
+       printk("DBG: good morning!\n");
+
        /* Download NVM configuration */
        config.type = TLV_TYPE_NVM;
        if (soc_type == QCA_WCN3990)

When you boot with this patch you'll see something like this:

[   15.531365] DBG: reading SoC version
[   15.544963] DBG: ZZZzzzzzzz
[   17.590282] Bluetooth: hci0: command 0xfc00 tx timeout
[   18.099110] DBG: good morning!

> In our case, we have an two fw files i.e. *.tlv and *.bin.
> tlv is an RAM image of the chip where as bin is an nvm image of the chip. so
> tlv will be of
> more size which require an  lot more time to dump the file in to chip,
> while dumping the tlv, we divide tlv as packet of size 245 bytes and send
> them as an command packet to the chip. chip should respond with an  command
> complete event.
> then only we will send the next packet. but size of the tlv is large, to
> optimize this we will
> not wait for the either an vendor specific event or an command complete
> event.

Let's make sure we have an accurate picture, which of the following is
correct:

1. the chip sends a command complete event after each packet, as an
optimization the BT driver doesn't wait for it

2. as an optimization the chip does not send a command complete event
and the driver has to deal with it

My understanding is that it's 2), but the wording above seems to
describe 1)

> But as we need to be on the sync, i.e. whether are we sending an correct
> packets or not,
> for the last fw packet we sent to the chip.. chip will to do an CRC check
> for the total no of packets received and respond with an vendor specific
> event.
> 
> We decode the vendor specific event and decide whether the fw download is
> success or not.  here we send an fw packet as command so stack expects an
> command complete event.
> where this is missing from the chip. this is  expected behavior from chip.
> 
> So currently i am inject an command complete event after receiving an vendor
> event for the last packet of the tlv.

And the same for the .bin if I'm not mistaken.

> This we inject only once for the last command packet sent to the chip.
> i don't think this will effect the btmon.

I don't know enough about btmon to comment on that, in any case Marcel
raised concerns.

And I think my comment that triggered this disucssion remains true:

> If the download of a firmware binary takes >= 2s (HCI_CMD_TIMEOUT) the
> timeout would still occur. If necessary this could be mitigated by
> injecting some command complete events during the firmware download.

Not sure it's a likely case, it might be an issue with larger firmware
files and/or slower UART speeds.

Thanks

Matthias

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