linux-kernel - Re: [PATCH v8 1/5] powerpc: Document details on H_SCM

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Message-ID: <CAPcyv4jXp1FocSe-fFBA_00TnsjPudrBCuHBfv+zwHA_R0353A@mail.gmail.com>
Date:   Wed, 27 May 2020 11:56:44 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Vaibhav Jain <vaibhav@...ux.ibm.com>
Cc:     linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        "Oliver O'Halloran" <oohall@...il.com>,
        Santosh Sivaraj <santosh@...six.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ira Weiny <ira.weiny@...el.com>
Subject: Re: [PATCH v8 1/5] powerpc: Document details on H_SCM_HEALTH hcall

On Tue, May 26, 2020 at 9:13 PM Vaibhav Jain <vaibhav@...ux.ibm.com> wrote:
>
> Add documentation to 'papr_hcalls.rst' describing the bitmap flags
> that are returned from H_SCM_HEALTH hcall as per the PAPR-SCM
> specification.
>

Please do a global s/SCM/PMEM/ or s/SCM/NVDIMM/. It's unfortunate that
we already have 2 ways to describe persistent memory devices, let's
not perpetuate a third so that "grep" has a chance to find
interrelated code across architectures. Other than that this looks
good to me.

> Cc: "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Ira Weiny <ira.weiny@...el.com>
> Signed-off-by: Vaibhav Jain <vaibhav@...ux.ibm.com>
> ---
> Changelog:
> v7..v8:
> * Added a clarification on bit-ordering of Health Bitmap
>
> Resend:
> * None
>
> v6..v7:
> * None
>
> v5..v6:
> * New patch in the series
> ---
>  Documentation/powerpc/papr_hcalls.rst | 45 ++++++++++++++++++++++++---
>  1 file changed, 41 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/powerpc/papr_hcalls.rst b/Documentation/powerpc/papr_hcalls.rst
> index 3493631a60f8..45063f305813 100644
> --- a/Documentation/powerpc/papr_hcalls.rst
> +++ b/Documentation/powerpc/papr_hcalls.rst
> @@ -220,13 +220,50 @@ from the LPAR memory.
>  **H_SCM_HEALTH**
>
>  | Input: drcIndex
> -| Out: *health-bitmap, health-bit-valid-bitmap*
> +| Out: *health-bitmap (r4), health-bit-valid-bitmap (r5)*
>  | Return Value: *H_Success, H_Parameter, H_Hardware*
>
>  Given a DRC Index return the info on predictive failure and overall health of
> -the NVDIMM. The asserted bits in the health-bitmap indicate a single predictive
> -failure and health-bit-valid-bitmap indicate which bits in health-bitmap are
> -valid.
> +the NVDIMM. The asserted bits in the health-bitmap indicate one or more states
> +(described in table below) of the NVDIMM and health-bit-valid-bitmap indicate
> +which bits in health-bitmap are valid. The bits are reported in
> +reverse bit ordering for example a value of 0xC400000000000000
> +indicates bits 0, 1, and 5 are valid.
> +
> +Health Bitmap Flags:
> +
> ++------+-----------------------------------------------------------------------+
> +|  Bit |               Definition                                              |
> ++======+=======================================================================+
> +|  00  | SCM device is unable to persist memory contents.                      |
> +|      | If the system is powered down, nothing will be saved.                 |
> ++------+-----------------------------------------------------------------------+
> +|  01  | SCM device failed to persist memory contents. Either contents were not|
> +|      | saved successfully on power down or were not restored properly on     |
> +|      | power up.                                                             |
> ++------+-----------------------------------------------------------------------+
> +|  02  | SCM device contents are persisted from previous IPL. The data from    |
> +|      | the last boot were successfully restored.                             |
> ++------+-----------------------------------------------------------------------+
> +|  03  | SCM device contents are not persisted from previous IPL. There was no |
> +|      | data to restore from the last boot.                                   |
> ++------+-----------------------------------------------------------------------+
> +|  04  | SCM device memory life remaining is critically low                    |
> ++------+-----------------------------------------------------------------------+
> +|  05  | SCM device will be garded off next IPL due to failure                 |
> ++------+-----------------------------------------------------------------------+
> +|  06  | SCM contents cannot persist due to current platform health status. A  |
> +|      | hardware failure may prevent data from being saved or restored.       |
> ++------+-----------------------------------------------------------------------+
> +|  07  | SCM device is unable to persist memory contents in certain conditions |
> ++------+-----------------------------------------------------------------------+
> +|  08  | SCM device is encrypted                                               |
> ++------+-----------------------------------------------------------------------+
> +|  09  | SCM device has successfully completed a requested erase or secure     |
> +|      | erase procedure.                                                      |
> ++------+-----------------------------------------------------------------------+
> +|10:63 | Reserved / Unused                                                     |
> ++------+-----------------------------------------------------------------------+
>
>  **H_SCM_PERFORMANCE_STATS**
>
> --
> 2.26.2
>