linux-kernel - Re: [PATCH v3 15/18] cxl/region: Add a dev

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Message-ID: <3e232358-cb42-4b17-9b00-f04eb517a79f@intel.com>
Date: Thu, 20 Feb 2025 10:35:58 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Robert Richter <rrichter@....com>
Cc: Alison Schofield <alison.schofield@...el.com>,
 Vishal Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>,
 Dan Williams <dan.j.williams@...el.com>, Davidlohr Bueso
 <dave@...olabs.net>, linux-cxl@...r.kernel.org,
 linux-kernel@...r.kernel.org, Gregory Price <gourry@...rry.net>,
 "Fabio M. De Francesco" <fabio.m.de.francesco@...ux.intel.com>,
 Terry Bowman <terry.bowman@....com>
Subject: Re: [PATCH v3 15/18] cxl/region: Add a dev_warn() on registration
 failure



On 2/14/25 9:35 AM, Jonathan Cameron wrote:
> On Tue, 11 Feb 2025 10:53:45 +0100
> Robert Richter <rrichter@....com> wrote:
> 
>> Esp. in complex system configurations with multiple endpoints and
>> interleaving setups it is hard to detect region setup failures as its
>> registration may silently fail. Add messages to show registration
>> failures.
>>
>> Example log message:
>>
>>   cxl region5: region sort successful
>>   cxl region5: mem0:endpoint5 decoder5.0 add: mem0:decoder5.0 @ 0 next: none nr_eps: 1 nr_targets: 1
>>   cxl_port endpoint5: decoder5.0: range: 0x22350000000-0x2634fffffff iw: 1 ig: 256
>>   cxl region5: pci0000:e0:port1 decoder1.2 add: mem0:decoder5.0 @ 0 next: mem0 nr_eps: 1 nr_targets: 1
>>   cxl region5: pci0000:e0:port1 iw: 1 ig: 256
>>   cxl region5: pci0000:e0:port1: decoder1.2 expected 0000:e0:01.2 at 0
>>   cxl endpoint5: failed to attach decoder5.0 to region5: -6
>>   cxl_port endpoint5: probe: 0
>>
>> Signed-off-by: Robert Richter <rrichter@....com>
>> Reviewed-by: Gregory Price <gourry@...rry.net>
>> Tested-by: Gregory Price <gourry@...rry.net>
> I'm in general fine with this, but we have previously been reluctant in
> some cases to go above dev_dbg.  Hence would like input from more
> people on this one.

If this error message has been helpful in determining the cause of issues when debugging a platform, I'm all for it.

Reviewed-by: Dave Jiang <dave.jiang@...el.com>
> 
> From me though
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> 
>> ---
>>  drivers/cxl/core/region.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
>> index ebcfbfe9eafc..3031d4773274 100644
>> --- a/drivers/cxl/core/region.c
>> +++ b/drivers/cxl/core/region.c
>> @@ -2147,6 +2147,12 @@ static int attach_target(struct cxl_region *cxlr,
>>  	rc = cxl_region_attach(cxlr, cxled, pos);
>>  	up_read(&cxl_dpa_rwsem);
>>  	up_write(&cxl_region_rwsem);
>> +
>> +	if (rc)
>> +		dev_warn(cxled->cxld.dev.parent,
>> +			"failed to attach %s to %s: %d\n",
>> +			dev_name(&cxled->cxld.dev), dev_name(&cxlr->dev), rc);
>> +
>>  	return rc;
>>  }
>>  
>