Re: [PATCH v2] coresight: etm4x: Fix crash observed on Qcom ETM parts with 'Low power override'

From: Leo Yan
Date: Wed Sep 14 2022 - 11:00:50 EST


On Wed, Sep 14, 2022 at 03:43:53PM +0100, Suzuki Kuruppassery Poulose wrote:

[...]

> > > + /*
> > > + * Some Qualcomm implementations require skipping powering up the trace unit,
> > > + * as the ETMs are in the same power domain as their CPU cores.
> > > + *
> > > + * Since the 'skip_power_up' flag is used inside 'etm4_init_arch_data' function,
> > > + * initialize it before the function is called.
> > > + */
> > > + if (fwnode_property_present(dev_fwnode(dev), "qcom,skip-power-up"))
> > > + drvdata->skip_power_up = true;
> > > +
> >
> > I personally think this sentence should be placed in the function
> > etm4_probe(), you need to move it just before smp call
> > etm4_init_arch_data(), this can allow DT property "qcom,skip-power-up"
> > to be respected.
>
> Or we could move this to init_iomem_access() and explicitly set the flag
> to true in init_sysreg_access().

Agreed, this is more clear.

[...]

> > A side topic, in the mainline kernel I found the value
> > "desc.access.io_mem" is always zero (see the initialized value in
> > etm4_probe() and etm4_init_sysreg_access()). Should we initialize
> > desc.access.io_mem to true in etm4_probe()?
>
> Thats not true. It is initialised at :
>
> etm4_init_iomem_access():
>
> *csa = CSDEV_ACCESS_IOMEM(drvdata->base);
>
> Where
>
> #define CSDEV_ACCESS_IOMEM(_addr) \
> ((struct csdev_access) { \
> .io_mem = true, \
> .base = (_addr), \
> })

Thanks a lot for explaination, sorry for noise.

Leo