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From: Jeff Moyer <jmoyer@redhat.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: linux-nvdimm@lists.01.org
Subject: Re: [RFC PATCH] libnvdimm: Update the meaning for persistence_domain values
Date: Wed, 15 Jan 2020 11:55:30 -0500
Message-ID: <x49o8v4oe0t.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <20200108064905.170394-1-aneesh.kumar@linux.ibm.com> (Aneesh Kumar K. V.'s message of "Wed, 8 Jan 2020 12:19:05 +0530")

"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?

> 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.

-Jeff
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Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-08  6:49 Aneesh Kumar K.V
2020-01-15 16:55 ` Jeff Moyer [this message]
2020-01-15 17:27   ` Aneesh Kumar K.V
2020-01-15 17:31     ` Aneesh Kumar K.V
2020-01-15 17:42       ` Jeff Moyer
2020-01-15 19:44       ` Dan Williams
2020-01-15 17:35     ` Jeff Moyer
2020-01-15 17:55       ` Aneesh Kumar K.V
2020-01-15 19:48         ` Dan Williams
2020-01-16  6:24           ` Aneesh Kumar K.V

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