Touchscreen failure with CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND

[Rafael J. Wysocki]

On Friday, April 21, 2017 06:37:31 PM Fabio Estevam wrote:
> On Fri, Apr 21, 2017 at 6:28 PM, Rafael J. Wysocki <rjw at rjwysocki.net> wrote:
> > On Friday, April 21, 2017 01:11:52 PM Fabio Estevam wrote:
> >> Hi,
> >>
> >> Running 4.11-rc7 on a imx6q-sabresd board I notice that egalax
> >> touchscreen stops generating evtest events after a random period of
> >> time.
> >>
> >> This problem can be avoided if I unselect CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND:
> >>
> >> --- a/arch/arm/configs/imx_v6_v7_defconfig
> >> +++ b/arch/arm/configs/imx_v6_v7_defconfig
> >> @@ -54,7 +54,6 @@ CONFIG_CMA=y
> >>  CONFIG_CMDLINE="noinitrd console=ttymxc0,115200"
> >>  CONFIG_KEXEC=y
> >>  CONFIG_CPU_FREQ=y
> >> -CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND=y
> >>  CONFIG_ARM_IMX6Q_CPUFREQ=y
> >>  CONFIG_CPU_IDLE=y
> >>  CONFIG_VFP=y
> >>
> >> With this change evtest always capture all touchscreen events. No
> >> single failure is seen.
> >>
> >> I could see the same behavior with all mainline kernels I tested (4.9 and 4.10).
> >>
> >> Any ideas as to how fix this bug when CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND=y?
> >
> > And which governor is the default otherwise?
> 
> When CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND=y is removed then the
> 'performance' governor is the default.

There you go.  Apparently, using frequencies below the max causes problems to
happen in the SoC.

Thanks,
Rafael