Messages in this thread Patch in this message | | | Date | Tue, 13 Sep 2022 18:52:32 +0800 | From | Leo Yan <> | Subject | Re: [PATCH v2] coresight: etm4x: Fix crash observed on Qcom ETM parts with 'Low power override' |
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Hi Bhupesh,
On Thu, Aug 25, 2022 at 10:52:32AM +0530, Bhupesh Sharma wrote: > Some Qualcomm ETM implementations require skipping powering up > the trace unit, as the ETMs are in the same power domain as > their CPU cores. > > Via commit 5214b563588e ("coresight: etm4x: Add support for > sysreg only devices"), the setting of 'skip_power_up' flag was > moved after the 'etm4_init_arch_data' function is called, whereas > the flag value is itself used inside the function. This causes > a crash when ETM mode 'Low-power state behavior override' is set > on some Qualcomm parts. > > Fix the same. > > Fixes: 5214b563588e ("coresight: etm4x: Add support for sysreg only devices") > Cc: Mike Leach <mike.leach@linaro.org> > Cc: Suzuki K Poulose <suzuki.poulose@arm.com> > Cc: Mathieu Poirier <mathieu.poirier@linaro.org> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Signed-off-by: Bhupesh Sharma <bhupesh.sharma@linaro.org> > --- > - v1 can be seen here: https://lore.kernel.org/lkml/20220803191236.3037591-1-bhupesh.sharma@linaro.org/ > - Addressed the review comments from Suzuki. > - Rebased on linux-next. > > drivers/hwtracing/coresight/coresight-etm4x-core.c | 13 +++++++++++-- > 1 file changed, 11 insertions(+), 2 deletions(-) > > diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c > index d39660a3e50c..14c1c7869795 100644 > --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c > +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c > @@ -977,6 +977,16 @@ static bool etm4_init_sysreg_access(struct etmv4_drvdata *drvdata, > if (!cpu_supports_sysreg_trace()) > return false; > > + /* > + * 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.
> /* > * ETMs implementing sysreg access must implement TRCDEVARCH. > */ > @@ -1951,8 +1961,7 @@ static int etm4_probe(struct device *dev, void __iomem *base, u32 etm_pid) > return -EINVAL; > > /* TRCPDCR is not accessible with system instructions. */ > - if (!desc.access.io_mem || > - fwnode_property_present(dev_fwnode(dev), "qcom,skip-power-up")) > + if (!desc.access.io_mem) > drvdata->skip_power_up = true;
I prefer to move the condition checking for "desc.access.io_mem" to etm4_init_sysreg_access(), this can make sure the flag skip_power_up is set correctly based on property of system register access.
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()?
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c index d39660a3e50c..cf2555c50abb 100644 --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c @@ -1939,6 +1939,7 @@ static int etm4_probe(struct device *dev, void __iomem *base, u32 etm_pid) if (drvdata->cpu < 0) return drvdata->cpu; + desc.access.io_mem = true; init_arg.drvdata = drvdata; init_arg.csa = &desc.access; init_arg.pid = etm_pid; Thanks, Leo
> major = ETM_ARCH_MAJOR_VERSION(drvdata->arch); > -- > 2.35.3 >
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