On Sun, Jun 23, 2024 at 08:21:00PM +0200, Marek Vasut wrote: > On 3/20/24 8:23 AM, Marek Vasut wrote: > > On STM32MP135F with XPT2046 touch controller attached to SPI bus, it has > > been observed that the touch controller locks up after Linux kernel has > > finished booting. Adding a dummy cycle on the SPI bus seems to mitigate > > the lock up. > > > > The XPTEK XPT2046 controller seems to be an identical clone of TI TSC2046, > > the datasheet seems to be a clone of the TI part as well, text seem to be > > word to word identical, except all the pictures have been drawn again. > > > > This touch controller is present e.g. on WaveShare 3.2inch RPi LCD (B) > > panel, the DTO provided by WaveShare uses 50 kHz SPI clock for this > > touch controller, which is unusually low and possibly might have been > > used as some sort of workaround for an issue. The SPI LCD on the same > > bus uses 16 MHz clock. > > > > SPI bus DT properties spi-cs-setup-delay-ns, spi-cs-hold-delay-ns, > > spi-cs-inactive-delay-ns, spi-rx-delay-us, spi-tx-delay-us set to > > range of 500ns..5us seem to have no impact on the behavior of the > > touch controller, the lock up always occurs. The STM32MP13xx SPI > > controller users GPIO control for the nCS pins. > > > > Since the dummy cycle happens after the controller has been put into > > power down mode and both ADC and REF regulators have been disabled, > > the cycle should have no impact on the configuration of the controller, > > i.e. it should be a NOP. > > > > It is unclear whether this problem is specific to this cloned XPT2046 > > controller, or whether this is also present on TSC2046. A test on > > either TSC2046 or ADS7846 would be very welcome. > > Hi, > > Are there still any open topics with this patch ? I am concerned that we are putting workaroud for a single controller into common function. Can we quirk it based on compatible? If not then I would like someone to run tests on other controllers. Unfortunately I do not have such hardware. Linus, do you have devices with ads7846 or tsc2046 by chance? Spitz? Thanks. -- Dmitry
