Re: [PATCH v10 2/8] coresight: etm3x: fix inconsistencies with sysfs configuration

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Sysfs interface for post-trace hardware state returns stale data due to active_config separation (ABI Breakage).
--

commit 729c4f4f776d1cbadf2571ee6a6363ece19f7a91
Author: Yeoreum Yun <yeoreum.yun@xxxxxxx>

coresight: etm3x: fix inconsistencies with sysfs configuration

This commit resolves sysfs configuration inconsistencies by separating the
configuration state into an active_config (for the current session) and config
(the configuration set via sysfs).

> diff --git a/drivers/hwtracing/coresight/coresight-etm3x-core.c b/drivers/hwtracing/coresight/coresight-etm3x-core.c
> --- a/drivers/hwtracing/coresight/coresight-etm3x-core.c
> +++ b/drivers/hwtracing/coresight/coresight-etm3x-core.c

[ ... ]

> @@ -565,7 +569,7 @@ static int etm_enable(struct coresight_device *csdev, struct perf_event *event,
>  static void etm_disable_hw(struct etm_drvdata *drvdata)
>  {
>  	int i;
> -	struct etm_config *config = &drvdata->config;
> +	struct etm_config *config = &drvdata->active_config;
>  	struct coresight_device *csdev = drvdata->csdev;
>  
>  	CS_UNLOCK(drvdata->csa.base);

[Severity: High]
Does this introduce a regression in the sysfs interface for post-trace
hardware state analysis?

By switching to active_config here, the post-trace sequencer and counter
states are saved into drvdata->active_config during etm_disable_hw():

drivers/hwtracing/coresight/coresight-etm3x-core.c:etm_disable_hw() {
	...
	/* Read back sequencer and counters for post trace analysis */
	config->seq_curr_state = (etm_readl(drvdata, ETMSQR) & ETM_SQR_MASK);

	for (i = 0; i < caps->nr_cntr; i++)
		config->cntr_val[i] = etm_readl(drvdata, ETMCNTVRn(i));
	...
}

However, when tracing is disabled, userspace reads from the sysfs interface
which still returns data from the stale drvdata->config:

drivers/hwtracing/coresight/coresight-etm3x-sysfs.c:seq_curr_state_show() {
	...
	val = config->seq_curr_state;
	...
}

Will this cause sysfs reads for seq_curr_state and cntr_val to return
stale or zeroed data instead of the actual hardware state?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260911-separate_etm_cfg_v2-v10-0-1b715d95927a@xxxxxxx?part=2