From mboxrd@z Thu Jan 1 00:00:00 1970 From: Balakrishna Godavarthi Subject: Re: [PATCH v5 1/5] Bluetooth: hci_qca: use wait_until_sent() for power pulses Date: Fri, 11 Jan 2019 20:02:00 +0530 Message-ID: <5e4b077bbcc81b624c851643bebc45f7@codeaurora.org> References: <20181220144639.15928-1-bgodavar@codeaurora.org> <20181220144639.15928-2-bgodavar@codeaurora.org> <20181222015947.GF261387@google.com> <20190109143822.GM14782@localhost> <2d4ee183e3c2fa964c14a5ac702043c0@codeaurora.org> <20190111005532.GC261387@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190111005532.GC261387@google.com> Sender: linux-kernel-owner@vger.kernel.org To: Matthias Kaehlcke Cc: Johan Hovold , 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 List-Id: linux-arm-msm@vger.kernel.org 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 >> > > > --- >> > > > 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. -- Regards Balakrishna.