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

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

[...]

quoted

quoted

+	/*
+	 * 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.

[...]

quoted

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

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