Subject: Re: [PATCH v7 02/13] coresight: etm4x: fix underflow for nrseqstate

From: Suzuki K Poulose <[email-masked]>
Date: Mon, 1 Jun 2026 10:52:45 +0100

On 19/05/2026 16:48, Yeoreum Yun wrote:
> TCRSEQEVR<n> is implemented only when TCRIDR5.NUMSEQSTATE is 0b100,
> in which case n ranges from 0 to 2; otherwise, TCRIDR5.NUMSEQSTATE is 0b000.
> 
> Therefore, drvdata->nrseqstate should be checked before entering the loop.

s/TCR/TRC/g ^^^ and every other patch in the series. Seem like you have 
been playing with the MMU code ;-)

> 
> Link: https://developer.arm.com/documentation/ihi0064/latest/ [0]
> Fixes: 2e1cdfe184b5 ("coresight-etm4x: Adding CoreSight ETM4x driver")
> Reviewed-by: Leo Yan <[email-masked]>
> Signed-off-by: Yeoreum Yun <[email-masked]>
> ---
>   .../hwtracing/coresight/coresight-etm4x-core.c | 18 ++++++++++--------
>   .../coresight/coresight-etm4x-sysfs.c          |  2 ++
>   2 files changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> index 1e3b0344dc00..94b9385e964a 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> @@ -542,9 +542,11 @@ static int etm4_enable_hw(struct etmv4_drvdata *drvdata)
>   	etm4x_relaxed_write32(csa, config->vissctlr, TRCVISSCTLR);
>   	if (drvdata->nr_pe_cmp)
>   		etm4x_relaxed_write32(csa, config->vipcssctlr, TRCVIPCSSCTLR);
> -	for (i = 0; i < drvdata->nrseqstate - 1; i++)
> -		etm4x_relaxed_write32(csa, config->seq_ctrl[i], TRCSEQEVRn(i));
> +
>   	if (drvdata->nrseqstate) {
> +		for (i = 0; i < drvdata->nrseqstate - 1; i++)
> +			etm4x_relaxed_write32(csa, config->seq_ctrl[i], TRCSEQEVRn(i));

Looking at this again, I think we are contemplating two different values 
from a single variable (blame the architecture). Instead, we should:

1. Disconnect number of TRCSEQEVRn from drvdata->nrseqstate, and add 
nr_seq_ctrls to drvdata and initialise this at probe.

for (i = 0; i < drvdata->nr_seq_ctrls; i++)

Suzuki

> +
>   		etm4x_relaxed_write32(csa, config->seq_rst, TRCSEQRSTEVR);
>   		etm4x_relaxed_write32(csa, config->seq_state, TRCSEQSTR);
>   	}
> @@ -1896,10 +1898,10 @@ static int etm4_cpu_save(struct coresight_device *csdev)
>   	if (drvdata->nr_pe_cmp)
>   		state->trcvipcssctlr = etm4x_read32(csa, TRCVIPCSSCTLR);
>   
> -	for (i = 0; i < drvdata->nrseqstate - 1; i++)
> -		state->trcseqevr[i] = etm4x_read32(csa, TRCSEQEVRn(i));
> -
>   	if (drvdata->nrseqstate) {
> +		for (i = 0; i < drvdata->nrseqstate - 1; i++)
> +			state->trcseqevr[i] = etm4x_read32(csa, TRCSEQEVRn(i));
> +
>   		state->trcseqrstevr = etm4x_read32(csa, TRCSEQRSTEVR);
>   		state->trcseqstr = etm4x_read32(csa, TRCSEQSTR);
>   	}
> @@ -2009,10 +2011,10 @@ static void etm4_cpu_restore(struct coresight_device *csdev)
>   	if (drvdata->nr_pe_cmp)
>   		etm4x_relaxed_write32(csa, state->trcvipcssctlr, TRCVIPCSSCTLR);
>   
> -	for (i = 0; i < drvdata->nrseqstate - 1; i++)
> -		etm4x_relaxed_write32(csa, state->trcseqevr[i], TRCSEQEVRn(i));
> -
>   	if (drvdata->nrseqstate) {
> +		for (i = 0; i < drvdata->nrseqstate - 1; i++)
> +			etm4x_relaxed_write32(csa, state->trcseqevr[i], TRCSEQEVRn(i));
> +
>   		etm4x_relaxed_write32(csa, state->trcseqrstevr, TRCSEQRSTEVR);
>   		etm4x_relaxed_write32(csa, state->trcseqstr, TRCSEQSTR);
>   	}
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
> index e9eeea6240d5..0e1ad175aa1e 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
> @@ -1395,6 +1395,8 @@ static ssize_t seq_idx_store(struct device *dev,
>   	struct etmv4_drvdata *drvdata = dev_get_drvdata(dev->parent);
>   	struct etmv4_config *config = &drvdata->config;
>   
> +	if (!drvdata->nrseqstate)
> +		return -ENOTSUPP;
>   	if (kstrtoul(buf, 16, &val))
>   		return -EINVAL;
>   	if (val >= drvdata->nrseqstate - 1)