From: Matthias Kaehlcke <mka@chromium.org>
To: Balakrishna Godavarthi <bgodavar@codeaurora.org>
Cc: Johan Hovold <johan@kernel.org>,
marcel@holtmann.org, johan.hedberg@gmail.com,
linux-kernel@vger.kernel.org, linux-bluetooth@vger.kernel.org,
hemantg@codeaurora.org, linux-arm-msm@vger.kernel.org,
Johan Hovold <jhovold@gmail.com>
Subject: Re: [PATCH v5 1/5] Bluetooth: hci_qca: use wait_until_sent() for power pulses
Date: Fri, 11 Jan 2019 15:38:12 -0800 [thread overview]
Message-ID: <20190111233812.GJ261387@google.com> (raw)
In-Reply-To: <5e4b077bbcc81b624c851643bebc45f7@codeaurora.org>
On Fri, Jan 11, 2019 at 08:02:00PM +0530, Balakrishna Godavarthi wrote:
> On 2019-01-11 06:25, Matthias Kaehlcke wrote:
> > On Thu, Jan 10, 2019 at 08:18:37PM +0530, Balakrishna Godavarthi wrote:
> > > Hi Johan,
> > >
> > > On 2019-01-09 20:08, Johan Hovold wrote:
> > > > On Fri, Dec 21, 2018 at 05:59:47PM -0800, Matthias Kaehlcke wrote:
> > > > > On Thu, Dec 20, 2018 at 08:16:35PM +0530, Balakrishna Godavarthi
> > > > > wrote:
> > > > > > wcn3990 requires a power pulse to turn ON/OFF along with
> > > > > > regulators. Sometimes we are observing the power pulses are sent
> > > > > > out with some time delay, due to queuing these commands. This is
> > > > > > causing synchronization issues with chip, which intern delay the
> > > > > > chip setup or may end up with communication issues.
> > > > > >
> > > > > > Signed-off-by: Balakrishna Godavarthi <bgodavar@codeaurora.org>
> > > > > > ---
> > > > > > drivers/bluetooth/hci_qca.c | 38 ++++++++++++++-----------------------
> > > > > > 1 file changed, 14 insertions(+), 24 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> > > > > > index f036c8f98ea3..5a07c2370289 100644
> > > > > > --- a/drivers/bluetooth/hci_qca.c
> > > > > > +++ b/drivers/bluetooth/hci_qca.c
> > > > > > @@ -1013,11 +1013,9 @@ static inline void host_set_baudrate(struct hci_uart *hu, unsigned int speed)
> > > > > > hci_uart_set_baudrate(hu, speed);
> > > > > > }
> > > > > >
> > > > > > -static int qca_send_power_pulse(struct hci_dev *hdev, u8 cmd)
> > > > > > +static int qca_send_power_pulse(struct hci_uart *hu, u8 cmd)
> > > > > > {
> > > > > > - struct hci_uart *hu = hci_get_drvdata(hdev);
> > > > > > - struct qca_data *qca = hu->priv;
> > > > > > - struct sk_buff *skb;
> > > > > > + int ret;
> > > > > >
> > > > > > /* These power pulses are single byte command which are sent
> > > > > > * at required baudrate to wcn3990. On wcn3990, we have an external
> > > > > > @@ -1029,19 +1027,16 @@ static int qca_send_power_pulse(struct hci_dev *hdev, u8 cmd)
> > > > > > * save power. Disabling hardware flow control is mandatory while
> > > > > > * sending power pulses to SoC.
> > > > > > */
> > > > > > - bt_dev_dbg(hdev, "sending power pulse %02x to SoC", cmd);
> > > > > > -
> > > > > > - skb = bt_skb_alloc(sizeof(cmd), GFP_KERNEL);
> > > > > > - if (!skb)
> > > > > > - return -ENOMEM;
> > > > > > -
> > > > > > + bt_dev_dbg(hu->hdev, "sending power pulse %02x to SoC", cmd);
> > > > > > hci_uart_set_flow_control(hu, true);
> > > > > > + ret = serdev_device_write_buf(hu->serdev, &cmd, sizeof(cmd));
> > > > > > + if (ret < 0) {
> > > > > > + bt_dev_err(hu->hdev, "failed to send power pulse %02x to SoC",
> > > > > > + cmd);
> > > > > > + return ret;
> > > > > > + }
> > > > > >
> > > > > > - skb_put_u8(skb, cmd);
> > > > > > - hci_skb_pkt_type(skb) = HCI_COMMAND_PKT;
> > > > > > -
> > > > > > - skb_queue_tail(&qca->txq, skb);
> > > > > > - hci_uart_tx_wakeup(hu);
> > > > > > + serdev_device_wait_until_sent(hu->serdev, 0);
> > > >
> > > > Again, do you really want to wait indefinitely here?
> > > >
> > > [Bala]: these commands are mandatory to turn ON or OFF the chip.
> > > so blocking to the max time is required.
> > > these commands are sent during the BT chip ON & OFF.
> > > in the latest series, i have flushed the uart before sending
> > > this
> > > commands
> > > so the uart FIFO(as just opened the port before calling this
> > > function) or the circular
> > > buffer will be empty and also i am disabling the flow
> > > control too.
> > > https://patchwork.kernel.org/patch/10744435/
> >
> > The commands may be mandatory for switching the chip on or off, but
> > what is better if there is a problem with sending them (e.g. a buggy
> > UART driver):
> >
> > 1. wait a reasonable time, report an error
> > 2. wait forever
> >
> > ?
> >
> > If the single byte command couldn't be sent after a few milliseconds,
> > it likely never will, waiting forever doesn't fix that. An error
> > report at least provides some information about the problem and the
> > driver is in a not-hanging state.
> >
> > Cheers
> >
> > Matthias
>
> [Bala]: will update this with a bound TIMEOUT value. But wait_until_sent()
> is void return
> type how could we know that the data is sent out on the lines.
Good point, I didn't check and expected it to return an error. If you
feel really motivated and have maintainer support you could possibly
change the API, however it seems this would be a somewhat larger
change.
I guess the next best thing to do is to proceed as if all data was
sent and if there was a problem it will likely manifest through
another error (especially for the ON pulse), which still seems better
than a hanging driver.
Cheers
Matthias
next prev parent reply other threads:[~2019-01-11 23:38 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-20 14:46 [PATCH v5 0/5] Bug fixes for Qualcomm BT chip wcn3990 Balakrishna Godavarthi
2018-12-20 14:46 ` [PATCH v5 1/5] Bluetooth: hci_qca: use wait_until_sent() for power pulses Balakrishna Godavarthi
2018-12-22 1:59 ` Matthias Kaehlcke
2018-12-26 6:31 ` Balakrishna Godavarthi
2018-12-26 22:21 ` Matthias Kaehlcke
2018-12-27 3:23 ` Balakrishna Godavarthi
2019-01-09 14:38 ` Johan Hovold
2019-01-10 14:48 ` Balakrishna Godavarthi
2019-01-11 0:55 ` Matthias Kaehlcke
2019-01-11 14:32 ` Balakrishna Godavarthi
2019-01-11 23:38 ` Matthias Kaehlcke [this message]
2019-01-14 10:25 ` Balakrishna Godavarthi
2018-12-20 14:46 ` [PATCH v5 2/5] Bluetooth: hci_qca: Deassert RTS while baudrate change command Balakrishna Godavarthi
2018-12-22 0:31 ` Matthias Kaehlcke
2018-12-26 5:45 ` Balakrishna Godavarthi
2018-12-26 20:25 ` Matthias Kaehlcke
2018-12-27 3:20 ` Balakrishna Godavarthi
2019-01-09 14:52 ` Johan Hovold
2019-01-10 14:34 ` Balakrishna Godavarthi
2019-01-10 14:39 ` Johan Hovold
2019-01-10 14:52 ` Balakrishna Godavarthi
2019-01-11 1:37 ` Matthias Kaehlcke
2019-01-11 15:07 ` Balakrishna Godavarthi
2019-01-11 23:56 ` Matthias Kaehlcke
2019-01-14 14:52 ` Balakrishna Godavarthi
2019-01-15 23:46 ` Matthias Kaehlcke
2019-01-17 16:09 ` Johan Hovold
2019-01-17 17:21 ` Matthias Kaehlcke
2019-01-18 9:44 ` Johan Hovold
2019-01-19 0:31 ` Matthias Kaehlcke
2019-01-21 8:56 ` Johan Hovold
2019-01-22 21:39 ` Matthias Kaehlcke
2019-01-21 14:41 ` Balakrishna Godavarthi
2019-01-22 21:53 ` Matthias Kaehlcke
2019-01-23 12:57 ` Balakrishna Godavarthi
2018-12-20 14:46 ` [PATCH v5 3/5] Bluetooth: hci_qca: Fix frame reassembly errors for wcn3990 Balakrishna Godavarthi
2018-12-20 14:46 ` [PATCH v5 4/5] Bluetooth: hci_qca: Disable IBS state machine and flush Tx buffer Balakrishna Godavarthi
2018-12-20 14:46 ` [PATCH v5 5/5] Bluetooth: btqca: inject command complete event during fw download Balakrishna Godavarthi
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