linux-kernel - Re: [PATCH 2/3] cxl: Set target type of region with that of root decoder

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Message-ID: <87o76ckb88.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date: Thu, 01 Aug 2024 14:28:55 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: Alison Schofield <alison.schofield@...el.com>
Cc: Dan Williams <dan.j.williams@...el.com>,  Dave Jiang
 <dave.jiang@...el.com>,  <linux-cxl@...r.kernel.org>,
  <linux-kernel@...r.kernel.org>,  Davidlohr Bueso <dave@...olabs.net>,
  "Jonathan Cameron" <jonathan.cameron@...wei.com>,  Vishal Verma
 <vishal.l.verma@...el.com>,  Ira Weiny <ira.weiny@...el.com>,  Alejandro
 Lucero <alucerop@....com>
Subject: Re: [PATCH 2/3] cxl: Set target type of region with that of root
 decoder

Alison Schofield <alison.schofield@...el.com> writes:

> On Mon, Jul 29, 2024 at 04:46:10PM +0800, Ying Huang wrote:
>> Now, the target type of region is hard-coded to HOSTONLYMEM, because
>> only type3 expanders are supported.  To support type2 accelerators,
>> set the target type of region root decoder with that of the root
>> decoder.
>
> Hi Ying,
>
> If the target type of a region is always the same as it's root decoder,
> (is it?)

IIUC, it is.  Do you know when they may be different?

> why do we store it as an attribute of the region. Can we look
> it up when needed?

Yes.  This is possible via to_cxl_root_decoder().  It's just
a little inconvenient.

> A bit more below -
>
>> 
>> Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
>> Suggested-by: Dan Williams <dan.j.williams@...el.com>
>> Cc: Davidlohr Bueso <dave@...olabs.net>
>> Cc: Jonathan Cameron <jonathan.cameron@...wei.com>
>> Cc: Dave Jiang <dave.jiang@...el.com>
>> Cc: Alison Schofield <alison.schofield@...el.com>
>> Cc: Vishal Verma <vishal.l.verma@...el.com>
>> Cc: Ira Weiny <ira.weiny@...el.com>
>> Cc: Alejandro Lucero <alucerop@....com>
>> ---
>>  drivers/cxl/core/region.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
>> index 21ad5f242875..9a483c8a32fd 100644
>> --- a/drivers/cxl/core/region.c
>> +++ b/drivers/cxl/core/region.c
>> @@ -2545,7 +2545,8 @@ static struct cxl_region *__create_region(struct cxl_root_decoder *cxlrd,
>>  		return ERR_PTR(-EBUSY);
>>  	}
>>  
>> -	return devm_cxl_add_region(cxlrd, id, mode, CXL_DECODER_HOSTONLYMEM);
>> +	return devm_cxl_add_region(cxlrd, id, mode,
>> +				   cxlrd->cxlsd.cxld.target_type);
>>  }
>
> Passing the 'cxlrd' and then a piece of the cxlrd (.target_type) looks
> redundant.

Yes.  We can remove the parameter.  Will change this if we still need
cxlr->type.  Thanks!

--
Best Regards,
Huang, Ying

>
> -- Alison
>
>>  
>>  static ssize_t create_pmem_region_store(struct device *dev,
>> -- 
>> 2.39.2
>>