On Saturday, January 17, 2015 at 01:22:10 AM, Kristina Martšenko wrote: > Reading a channel through sysfs, or starting a buffered capture, can > occasionally turn off the touchscreen. > > This is because the read_raw() and buffer preenable()/postdisable() > callbacks unschedule current conversions on all channels. If a delay > channel happens to schedule a touchscreen conversion at the same time, > the conversion gets cancelled and the touchscreen sequence stops. > > This is probably related to this note from the reference manual: > > "If a delay group schedules channels to be sampled and a manual > write to the schedule field in CTRL0 occurs while the block is > discarding samples, the LRADC will switch to the new schedule > and will not sample the channels that were previously scheduled. > The time window for this to happen is very small and lasts only > while the LRADC is discarding samples." > > So make the callbacks only unschedule conversions for the channels they > use. This means channel 0 for read_raw() and channels 0-5 for the buffer > (if the touchscreen is enabled). Since the touchscreen uses different > channels (6 and 7), it no longer gets turned off. > > This is tested and fixes the issue on i.MX28, but hasn't been tested on > i.MX23. > > Signed-off-by: Kristina Martšenko <kristina.martsenko@xxxxxxxxx> Reviewed-by: Marek Vasut <marex@xxxxxxx> Best regards, Marek Vasut _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
