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

[Bhupesh Sharma]

On 8/25/22 10:52 AM, 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@xxxxxxxxxx>
> Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Bhupesh Sharma <bhupesh.sharma@xxxxxxxxxx>
> ---
>   - v1 can be seen here: https://lore.kernel.org/lkml/20220803191236.3037591-1-bhupesh.sharma@xxxxxxxxxx/
>   - 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;
> +
>   	/*
>   	 * 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;
>   
>   	major = ETM_ARCH_MAJOR_VERSION(drvdata->arch);

Gentle ping. Any review comments on the v2?

Thanks,
Bhupesh