Messages in this thread | | | Date | Fri, 14 Dec 2018 18:02:40 +0530 | From | Balakrishna Godavarthi <> | Subject | Re: [PATCH v3 1/4] Bluetooth: hci_qca: use wait_until_sent() for power pulses |
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Hi Johan,
On 2018-12-12 22:12, Johan Hovold wrote: > On Thu, Dec 06, 2018 at 04:10:07PM +0530, Balakrishna Godavarthi wrote: >> Hi Johan, >> >> On 2018-12-05 11:55, Johan Hovold wrote: >> > On Fri, Nov 30, 2018 at 08:32:44PM +0530, Balakrishna Godavarthi wrote: > >> >> + ret = serdev_device_write(hu->serdev, &cmd, sizeof(cmd), 0); >> > >> > You're still using 0 as a timeout here which is broken, as I already >> > told you. >> >> [Bala]: got the change now will update to timeout to non zero value. >> >> > From 4.21 this will result in an indefinite timeout, but currently >> > implies not to wait for a full write buffer to drain at all. >> > >> > As I also mentioned, you need to to make sure to call >> > serdev_device_write_wakeup() in the write_wakup() path if you are going >> > to use serdev_device_write() at all. >> >> [Bala]: this where i am confused. >> calling serdev_device_write is calling an wakeup internally. >> below is the flow >> >> ttyport_write_buf: >> * calling serdev_device_write() will call write_buf() >> in >> this call we are enabling bit "TTY_DO_WRITE_WAKEUP" and calling >> write() >> i.e. uart_write() where we call in start_tx. this >> will >> go to the vendor specific write where in isr we call >> uart_write_wakeup() >> >> https://elixir.bootlin.com/linux/latest/source/drivers/tty/serial/qcom_geni_serial.c#L756 >> >> >> uart_write_wakeup()->ttyport_write_wakeup()->serdev_controller_write_wakeup()->hci_uart_write_wakeup()->hci_uart_tx_wakeup() >> >> the above is flow when serdev_device_write() is called, it is >> indirectly calling serdev_write_wakeup(). > > No, serdev_device_write_wakeup() is currently not called in this path, > which means you cannot use serdev_device_write(). > >> Why actual we need to call an serdev_write_wakeup() is this >> wakeup related to the UART port or for the BT chip. > > serdev_device_write_wakeup() is where a writer blocked on a full write > buffer in serdev_device_write() is woken up. > > Johan
Is it preferred to use and serdev_device_write_buf() followed by serdev_device_wait_until_sent() or do we required an write_wakeup() called before writing into serdev_device_write_buf()
-- Regards Balakrishna.
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