Re: [RFC PATCH] libnvdimm: Update the meaning for persistence_domain values

["Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>]

On 1/15/20 10:25 PM, Jeff Moyer wrote:
> "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> writes:
> 
>> Currently, kernel shows the below values
>> 	"persistence_domain":"cpu_cache"
>> 	"persistence_domain":"memory_controller"
>> 	"persistence_domain":"unknown"
>>
>> This patch updates the meaning of these values such that
>>
>> "cpu_cache" indicates no extra instructions is needed to ensure the persistence
>> of data in the pmem media on power failure.
>>
>> "memory_controller" indicates platform provided instructions need to be issued
>> as per documented sequence to make sure data flushed is guaranteed to be on pmem
>> media in case of system power loss.
>>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
>> ---
>>   arch/powerpc/platforms/pseries/papr_scm.c | 7 ++++++-
>>   include/linux/libnvdimm.h                 | 6 +++---
>>   2 files changed, 9 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
>> index c2ef320ba1bf..26a5ef263758 100644
>> --- a/arch/powerpc/platforms/pseries/papr_scm.c
>> +++ b/arch/powerpc/platforms/pseries/papr_scm.c
>> @@ -360,8 +360,13 @@ static int papr_scm_nvdimm_init(struct papr_scm_priv *p)
>>   
>>   	if (p->is_volatile)
>>   		p->region = nvdimm_volatile_region_create(p->bus, &ndr_desc);
>> -	else
>> +	else {
>> +		/*
>> +		 * We need to flush things correctly to guarantee persistance
>> +		 */
>> +		set_bit(ND_REGION_PERSIST_MEMCTRL, &ndr_desc.flags);
>>   		p->region = nvdimm_pmem_region_create(p->bus, &ndr_desc);
>> +	}
>>   	if (!p->region) {
>>   		dev_err(dev, "Error registering region %pR from %pOF\n",
>>   				ndr_desc.res, p->dn);
> 
> Would you also update of_pmem to indicate the persistence domain,
> please?
> 

sure.


>> diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
>> index f2a33f2e3ba8..9126737377e1 100644
>> --- a/include/linux/libnvdimm.h
>> +++ b/include/linux/libnvdimm.h
>> @@ -52,9 +52,9 @@ enum {
>>   	 */
>>   	ND_REGION_PERSIST_CACHE = 1,
>>   	/*
>> -	 * Platform provides mechanisms to automatically flush outstanding
>> -	 * write data from memory controler to pmem on system power loss.
>> -	 * (ADR)
>> +	 * Platform provides instructions to flush data such that on completion
>> +	 * of the instructions, data flushed is guaranteed to be on pmem even
>> +	 * in case of a system power loss.
> 
> I find the prior description easier to understand.


I was trying to avoid the term 'automatically, 'memory controler' and 
ADR. Can I update the above as

/*
  * Platform provides mechanisms to flush outstanding write data
  * to pmem on system power loss.
  */


-aneesh
_______________________________________________
Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org
To unsubscribe send an email to linux-nvdimm-leave@lists.01.org