Messages in this thread | | | Date | Mon, 14 Jan 2019 15:55:41 +0530 | From | Balakrishna Godavarthi <> | Subject | Re: [PATCH v5 1/5] Bluetooth: hci_qca: use wait_until_sent() for power pulses |
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Hi Matthias,
On 2019-01-12 05:08, Matthias Kaehlcke wrote: > 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
[Bala]: sure, will add the timeout to one second and if data didn't sent to the lines anyways we will get an version command timeouts errors.
-- Regards Balakrishna.
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