Re: [PATCH v10 1/8] coresight: etm4x: fix inconsistencies with sysfs configuration

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Hardware counter values (`cntr_val`) read back during trace disable are saved to the temporary runtime `active_config` instead of the sysfs-visible `config` structure, permanently losing the post-session hardware state.
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commit 293039b149bb540c924b83cd181604cbff99de4c
Author: Yeoreum Yun <yeoreum.yun@arm.com>

coresight: etm4x: fix inconsistencies with sysfs configuration

This commit addresses inconsistencies in ETM4x sysfs configuration by
separating the configuration into an active_config for the current session
and a config for sysfs. It updates the enable/disable paths to use the
active session configuration to prevent corruption from concurrent access.

> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c

[ ... ]

> @@ -1044,7 +1054,7 @@ static void etm4_disable_trace_unit(struct etmv4_drvdata *drvdata)
>  static void etm4_disable_hw(struct etmv4_drvdata *drvdata)
>  {
>  	u32 control;
> -	struct etmv4_config *config = &drvdata->config;
> +	struct etmv4_config *config = &drvdata->active_config;
>  	struct coresight_device *csdev = drvdata->csdev;
>  	struct csdev_access *csa = &csdev->access;
>  	int i;

[Severity: High]
Does this change cause the post-session hardware counter values to be lost?

Later in etm4_disable_hw(), the hardware counter values are read back from
the device:

	/* read back the current counter values */
	for (i = 0; i < caps->nr_cntr; i++) {
		config->cntr_val[i] =
			etm4x_relaxed_read32(csa, TRCCNTVRn(i));
	}

Because config now points to drvdata->active_config, the updated counter
values are saved to the temporary active session configuration instead of
the primary sysfs configuration.

When a user subsequently reads the counter value via the sysfs interface
in cntr_val_show():

	struct etmv4_config *config = &drvdata->config;
	...
	val = config->cntr_val[idx];

they will read from the static drvdata->config, which never receives these
read-back values and will instead return the initial configuration value.
Should the read-back hardware state be synchronized back to drvdata->config
when the trace is disabled?

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Sashiko AI review · https://sashiko.dev/#/patchset/20260911-separate_etm_cfg_v2-v10-0-1b715d95927a@arm.com?part=1