lkml.org 
[lkml]   [2018]   [Dec]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3 1/4] Bluetooth: hci_qca: use wait_until_sent() for power pulses
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.

\
 
 \ /
  Last update: 2018-12-14 13:33    [W:0.121 / U:0.624 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site