On Wed, Nov 25, 2009 at 5:06 PM, Michael Trimarchi < trimar...@gandalf.sssup.it> wrote:
> Hi, > > Michael Trimarchi wrote: > > Hi all, > > > > I would like to know how android deal with the problem of data buffering > > during mobile phone suspend. > > This is a scenario: > > > > linux start to suspend and no wakelock are acquired by any subsystem and > > the application that read from > > the serial device is froozen, but the application does't know exaclty > > when it will go to sleep so it can > > give this info to the gsm modem (rise up RTS). The modem is connected to > > the serial and try to send data, > > linux buffer it but doesnt't give any info to the application. It can be > > happen or there is somenthing > > wrong on this scenario? > > > > Michael > > > I have seen that the msn kernel serial driver acquire a wake lock on rx > path > but it is not clear how it force the gsm to start to buffering during > suspend. > If the gsm has hw flow control the driver must block the gsm to trasmit > to the host > to avoid data lost. Is this correct? > If you want to put the apps CPU to sleep (for example, power-collapse-from-suspend, which is on the linux suspend path), and continue to be ready to receive RX data over a uart, then you'll want to keep the uart clocked on and make the uart irq a wakeup irq. Keeping the uart clocked on usually involves keeping TCXO clock on and at least ~30mA current draw, which is not ideal. So many platforms (eg Dream, Sapphire) will MUX a wakeup GPIO to the uart CTS or RX pin that we can wakeup on without keeping the uart clocked on. Our msm_serial_hs uart driver has the ability to handle all of the above. There are further comments on the strategy in the source file. Nick > > Michael > > > --~--~---------~--~----~------------~-------~--~----~ > > unsubscribe: > > android-kernel+unsubscr...@googlegroups.com<android-kernel%2bunsubscr...@googlegroups.com> > > website: http://groups.google.com/group/android-kernel > > -~----------~----~----~----~------~----~------~--~--- > > > > > > > > -- > unsubscribe: > android-kernel+unsubscr...@googlegroups.com<android-kernel%2bunsubscr...@googlegroups.com> > website: http://groups.google.com/group/android-kernel > -- unsubscribe: android-kernel+unsubscr...@googlegroups.com website: http://groups.google.com/group/android-kernel
