Re: [PATCH v5 04/12] coresight: etm4x: exclude ss_status from drvdata->config

[Suzuki K Poulose <suzuki.poulose@arm.com>]

On 16/04/2026 16:51, Leo Yan wrote:
> On Wed, Apr 15, 2026 at 05:55:20PM +0100, Yeoreum Yun wrote:
> 
> [...]
> 
>> @@ -573,11 +573,9 @@ static int etm4_enable_hw(struct etmv4_drvdata *drvdata)
>>   		etm4x_relaxed_write32(csa, config->res_ctrl[i], TRCRSCTLRn(i));
>>   
>>   	for (i = 0; i < caps->nr_ss_cmp; i++) {
>> -		/* always clear status bit on restart if using single-shot */
>> -		if (config->ss_ctrl[i] || config->ss_pe_cmp[i])
>> -			config->ss_status[i] &= ~TRCSSCSRn_STATUS;
>>   		etm4x_relaxed_write32(csa, config->ss_ctrl[i], TRCSSCCRn(i));
>> -		etm4x_relaxed_write32(csa, config->ss_status[i], TRCSSCSRn(i));
>> +		/* always clear status and pending bits on restart if using single-shot */
>> +		etm4x_relaxed_write32(csa, 0x0, TRCSSCSRn(i));
> 
> In Arm ARM, D24.4.60 TRCSSCSR<n>, bits[0..3] are RO.  I think it is
> fine for directly clear the regiser with zero (means it will only
> clear status / pending bits).
> 
> [...]
> 
>> @@ -1841,10 +1839,11 @@ static ssize_t sshot_status_show(struct device *dev,
>>   {
>>   	unsigned long val;
>>   	struct etmv4_drvdata *drvdata = dev_get_drvdata(dev->parent);
>> +	const struct etmv4_caps *caps = &drvdata->caps;
>>   	struct etmv4_config *config = &drvdata->config;
>>   
>>   	raw_spin_lock(&drvdata->spinlock);
>> -	val = config->ss_status[config->ss_idx];
>> +	val = caps->ss_cmp[config->ss_idx];
>>   	raw_spin_unlock(&drvdata->spinlock);
>>   	return scnprintf(buf, PAGE_SIZE, "%#lx\n", val);
>>   }
> 
> This sysfs knob never can print out a realtime status for sshot, I am

Won't it give the status, when the ETM was disabled (and saved back to
config), for as sysfs mode operation, where the user collects
information about the status via sysfs ? ( The question of if someone
actually makes use of this is a different question )


Cheers
Suzuki


> fine for only printing caps->ss_cmp, this can avoid any misleading.
> 
> @Suzuki, @Mike, do you agree with the change above?
> 
> If maintainers agree with this, as Jie suggested, it is good to add a
> comment in the code and update the document:
> 
>    Documentation/trace/coresight/coresight-etm4x-reference.rst
> 
> Thanks,
> Leo