Re: [PATCH] coresight: platform: check the availability of the endpoint before parse

[Jie Gan <jie.gan@oss.qualcomm.com>]

Hi Leo,

On 3/20/2026 4:25 PM, Leo Yan wrote:
> On Fri, Mar 20, 2026 at 03:31:12PM +0800, Jie Gan wrote:
>> Check endpoint availability before parsing it. If parsing a connected
>> endpoint fails, the probe is deferred until the endpoint becomes
>> available, or eventually fails.
> 
> I want to clarify a bit the failure flow.
> 
> Does this mean coresight_find_device_by_fwnode() returns NULL when the
> remote device is not found, resulting in -EPROBE_DEFER, but the probe
> never waits for the remote device to become available?

It's about the coresight_find_device_by_fwnode() returns NULL, resulting 
in -EPROBE_DEFER. So the probe process will re-start after several 
seconds, but always failed because we have a "disabled" device node in 
DT(we can see this device in DT, but it never becomes available). It's 
ok if the device only has one remote device, but has issue with more 
than one remote devices.

Consider below situation:

       device0
    |          |
   device1  device2(status = "disabled")

The probe of device0 succeeds only when device1 and device2 are 
available at probe time. But I think it's ok to probe the device0 only 
with device1 available.

Thanks,
Jie

> 
>> In some legacy cases, a replicator
>> has two output ports where one is disabled and the other is available.
>> The replicator probe always fails because the disabled endpoint never
>> becomes available for parsing. In addition, there is no need to defer
>> probing a device that is connected to a disabled device, which improves
>> probe performance.
>>
>> Signed-off-by: Jie Gan <jie.gan@oss.qualcomm.com>
>> ---
>>   drivers/hwtracing/coresight/coresight-platform.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/drivers/hwtracing/coresight/coresight-platform.c
>> index 0ca3bd762454..e337b6e2bf32 100644
>> --- a/drivers/hwtracing/coresight/coresight-platform.c
>> +++ b/drivers/hwtracing/coresight/coresight-platform.c
>> @@ -220,6 +220,8 @@ static int of_coresight_parse_endpoint(struct device *dev,
>>   		rparent = of_coresight_get_port_parent(rep);
>>   		if (!rparent)
>>   			break;
>> +		if (!of_device_is_available(rparent))
>> +			break;
>>   		if (of_graph_parse_endpoint(rep, &rendpoint))
>>   			break;
>>   
>>
>> ---
>> base-commit: b5d083a3ed1e2798396d5e491432e887da8d4a06
>> change-id: 20260320-add-availability-check-4cb2ee6e520b
>>
>> Best regards,
>> -- 
>> Jie Gan <jie.gan@oss.qualcomm.com>
>>