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Date:   Tue, 29 Jan 2019 18:38:12 +0530
From:   Balakrishna Godavarthi <bgodavar@codeaurora.org>
To:     Matthias Kaehlcke <mka@chromium.org>
Cc:     marcel@holtmann.org, johan.hedberg@gmail.com, johan@kernel.org,
        linux-kernel@vger.kernel.org, linux-bluetooth@vger.kernel.org,
        hemantg@codeaurora.org, linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH v9 1/3] Bluetooth: hci_qca: use wait_until_sent() for
 power pulses
In-Reply-To: <20190128174750.GG81583@google.com>
References: <20190124120808.8275-1-bgodavar@codeaurora.org>
 <20190124120808.8275-2-bgodavar@codeaurora.org>
 <20190125011412.GE81583@google.com>
 <0fac93a13ee445569659075cf467ad4d@codeaurora.org>
 <20190128174750.GG81583@google.com>
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Hi Matthias,

On 2019-01-28 23:17, Matthias Kaehlcke wrote:
> On Mon, Jan 28, 2019 at 07:19:56PM +0530, Balakrishna Godavarthi wrote:
>> Hi Matthias,
>> 
>> On 2019-01-25 06:44, Matthias Kaehlcke wrote:
>> > On Thu, Jan 24, 2019 at 05:38:06PM +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>
>> > > ---
>> > > Changes in v9:
>> > >  * Reverted to 100us sleep.
>> > >  * used inline call msecs_to_jiffies()
>> > >
>> > > Changes in v8:
>> > >  * Updated 1 second timeout instead of indefinite wait.
>> > >
>> > > Changes in v7:
>> > >  *  updated the wait time to 5 ms after sending power pulses.
>> > >
>> > > Changes in v6:
>> > >  * added serdev_device_write_flush() in qca_send_power_pulse
>> > >    instead during the power off pulse.
>> > >
>> > > Changes in v5:
>> > >  * added serdev_device_write_flush() in qca_power_off().
>> > > ---
>> > >  drivers/bluetooth/hci_qca.c | 40
>> > > +++++++++++++++----------------------
>> > >  1 file changed, 16 insertions(+), 24 deletions(-)
>> > >
>> > > diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
>> > > index f036c8f98ea3..c08f4d105e73 100644
>> > > --- a/drivers/bluetooth/hci_qca.c
>> > > +++ b/drivers/bluetooth/hci_qca.c
>> > > @@ -60,6 +60,7 @@
>> > >  #define IBS_WAKE_RETRANS_TIMEOUT_MS	100
>> > >  #define IBS_TX_IDLE_TIMEOUT_MS		2000
>> > >  #define BAUDRATE_SETTLE_TIMEOUT_MS	300
>> > > +#define POWER_PULSE_TRANS_TIMEOUT_MS	1000
>> >
>> > I still doubt that this mega-timeout of 1s is needed, but it shouldn't
>> > do any harm either, so whatever ...
>> >
>> 
>> [Bala]: for now let us have it. we can improve it in the improvement 
>> patch
>>         based on the results.
> 
> Fine.
> 
> With the UART buffer flushed and flow control disabled I wonder though
> what makes you think that it could take longer than a few milliseconds
> for the byte being put on the wire, short of a bug in the UART driver
> or hardware, which (if it existed) shouldn't be worked around here.
> 

[Bala]: i don't see any issue decreasing to milliseconds. will update it 
to 100ms.

>> > >  /* susclk rate */
>> > >  #define SUSCLK_RATE_32KHZ	32768
>> > > @@ -1013,11 +1014,10 @@ 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;
>> > > +	int timeout = msecs_to_jiffies(POWER_PULSE_TRANS_TIMEOUT_MS);
>> > >
>> > >  	/* These power pulses are single byte command which are sent
>> > >  	 * at required baudrate to wcn3990. On wcn3990, we have an external
>> > > @@ -1029,21 +1029,19 @@ 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 controller", cmd);
>> > >
>> > > +	serdev_device_write_flush(hu->serdev);
>> > >  	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", 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, timeout);
>> > >
>> > > -	/* Wait for 100 uS for SoC to settle down */
>> > > +	/* Wait for 100 uS for SoC to settle down for the received byte. */
>> >
>> > I don't think 'for the received byte' adds much value here. If you
>> > respin anyway I'd suggest to leave the comment as is.
>> >
>> 
>> [Bala]: will update.
>> 
>> > >  	usleep_range(100, 200);
>> > >  	hci_uart_set_flow_control(hu, false);
>> > >
>> > > @@ -1116,7 +1114,6 @@ static int qca_set_speed(struct hci_uart *hu,
>> > > enum qca_speed_type speed_type)
>> > >
>> > >  static int qca_wcn3990_init(struct hci_uart *hu)
>> > >  {
>> > > -	struct hci_dev *hdev = hu->hdev;
>> > >  	struct qca_serdev *qcadev;
>> > >  	int ret;
>> > >
>> > > @@ -1139,12 +1136,12 @@ static int qca_wcn3990_init(struct hci_uart
>> > > *hu)
>> > >
>> > >  	/* Forcefully enable wcn3990 to enter in to boot mode. */
>> > >  	host_set_baudrate(hu, 2400);
>> > > -	ret = qca_send_power_pulse(hdev, QCA_WCN3990_POWEROFF_PULSE);
>> > > +	ret = qca_send_power_pulse(hu, QCA_WCN3990_POWEROFF_PULSE);
>> > >  	if (ret)
>> > >  		return ret;
>> > >
>> > >  	qca_set_speed(hu, QCA_INIT_SPEED);
>> > > -	ret = qca_send_power_pulse(hdev, QCA_WCN3990_POWERON_PULSE);
>> > > +	ret = qca_send_power_pulse(hu, QCA_WCN3990_POWERON_PULSE);
>> > >  	if (ret)
>> > >  		return ret;
>> > >
>> > > @@ -1274,13 +1271,8 @@ static const struct qca_vreg_data
>> > > qca_soc_data = {
>> > >
>> > >  static void qca_power_shutdown(struct hci_uart *hu)
>> > >  {
>> > > -	struct serdev_device *serdev = hu->serdev;
>> > > -	unsigned char cmd = QCA_WCN3990_POWEROFF_PULSE;
>> > > -
>> > >  	host_set_baudrate(hu, 2400);
>> > > -	hci_uart_set_flow_control(hu, true);
>> > > -	serdev_device_write_buf(serdev, &cmd, sizeof(cmd));
>> > > -	hci_uart_set_flow_control(hu, false);
>> > > +	qca_send_power_pulse(hu, QCA_WCN3990_POWEROFF_PULSE);
>> > >  	qca_power_setup(hu, false);
>> > >  }
>> > >
>> >
>> > Looks good to me besides possible minor improvements:
>> >
>> > Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
>> 

-- 
Regards
Balakrishna.