linux-kernel - Re: [Linux-nvdimm] [PATCH 04/21] nd: create an 'nd_bus' from an 'nfit

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Date:	Wed, 22 Apr 2015 13:00:02 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Toshi Kani <toshi.kani@...com>
Cc:	Linda Knippers <linda.knippers@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>
Subject: Re: [Linux-nvdimm] [PATCH 04/21] nd: create an 'nd_bus' from an 'nfit_desc'

On Wed, Apr 22, 2015 at 12:38 PM, Toshi Kani <toshi.kani@...com> wrote:
> On Wed, 2015-04-22 at 12:28 -0700, Dan Williams wrote:
>> On Wed, Apr 22, 2015 at 11:23 AM, Toshi Kani <toshi.kani@...com> wrote:
>> > On Wed, 2015-04-22 at 11:20 -0700, Dan Williams wrote:
>> >> On Wed, Apr 22, 2015 at 11:00 AM, Linda Knippers <linda.knippers@...com> wrote:
>> >> Wait, point of clarification, DCRs (dimm-control-regions) have RFICs,
>> >> not MEMDEVs (memory-device-to-spa-mapping).  Toshi's original report
>> >> was that an NFIT with a SPA+MEMDEV was failing to enable a PMEM
>> >> device.  That specific problem can be fixed by either deleting the
>> >> MEMDEV, or adding a DCR.
>> >
>> > By a DCR, do you mean a DCR structure or SPA with Control Region GUID?
>>
>> Hmm, I meant a DCR as defined below.  I agree you would not need a "SPA-DCR".
>>
>> > Adding a DCR structure does not solve this issue since it requires SPA
>> > with Control Region GUID, which battery-backed DIMMs do not have.
>>
>> I would not go that far, half of a DCR entry is relevant for any
>> NVDIMM, and half is only relevant if a DIMM offers BLK access:
>>
>> struct acpi_nfit_dcr {
>>         u16 type;
>>         u16 length;
>>         u16 dcr_index;
>>         u16 vendor_id;
>>         u16 device_id;
>>         u16 revision_id;
>>         u16 sub_vendor_id;
>>         u16 sub_device_id;
>>         u16 sub_revision_id;
>>         u8 reserved[6];
>>         u32 serial_number;
>>         u16 fic;
>> <<<<< BLK relevant fields start here <<<<<
>>         u16 num_bcw;
>>         u64 bcw_size;
>>         u64 cmd_offset;
>>         u64 cmd_size;
>>         u64 status_offset;
>>         u64 status_size;
>>         u16 flags;
>>         u8 reserved2[6];
>> };
>
> Yes, we do have a DCR entry.  But we do not have a SPA-DCR.

Got it. will fix.
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