linux-kernel - Re: [PATCH 08/20] lightnvm: complete geo structure with maxoc*

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Message-ID: <6AB3CE71-8BC1-4D6E-A379-A7CFDF61B7FE@cnexlabs.com>
Date:   Thu, 22 Feb 2018 10:03:30 +0000
From:   Javier Gonzalez <javier@...xlabs.com>
To:     Matias Bjørling <mb@...htnvm.io>
CC:     "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>
Subject: Re: [PATCH 08/20] lightnvm: complete geo structure with maxoc*


Javier

> On 22 Feb 2018, at 11.00, Matias Bjørling <mb@...htnvm.io> wrote:
> 
> On 02/22/2018 10:52 AM, Javier Gonzalez wrote:
>>> On 22 Feb 2018, at 10.45, Matias Bjørling <mb@...htnvm.io> wrote:
>>> 
>>> On 02/22/2018 08:55 AM, Javier Gonzalez wrote:
>>>>> On 22 Feb 2018, at 08.45, Matias Bjørling <mb@...htnvm.io> wrote:
>>>>> 
>>>>> On 02/21/2018 10:26 AM, Javier González wrote:
>>>>>> Complete the generic geometry structure with the maxoc and maxocpu
>>>>>> felds, present in the 2.0 spec.
>>>>>> Signed-off-by: Javier González <javier@...xlabs.com>
>>>>>> ---
>>>>>>  drivers/nvme/host/lightnvm.c | 4 ++++
>>>>>>  include/linux/lightnvm.h     | 2 ++
>>>>>>  2 files changed, 6 insertions(+)
>>>>>> diff --git a/drivers/nvme/host/lightnvm.c b/drivers/nvme/host/lightnvm.c
>>>>>> index cca32da05316..9c1f8225c4e1 100644
>>>>>> --- a/drivers/nvme/host/lightnvm.c
>>>>>> +++ b/drivers/nvme/host/lightnvm.c
>>>>>> @@ -318,6 +318,8 @@ static int nvme_nvm_setup_12(struct nvme_nvm_id12 *id,
>>>>>>  	dev_geo->c.ws_min = sec_per_pg;
>>>>>>  	dev_geo->c.ws_opt = sec_per_pg;
>>>>>>  	dev_geo->c.mw_cunits = 8;		/* default to MLC safe values */
>>>>>> +	dev_geo->c.maxoc = dev_geo->all_luns;	/* default to 1 chunk per LUN */
>>>>>> +	dev_geo->c.maxocpu = 1;			/* default to 1 chunk per LUN */
>>>>> 
>>>>> One can't assume that it is 1 open chunk per lun. If you need this for specific hardware, make a quirk for it.
>>>> Which default you want for 1.2 if not specified then? I use 1 because it
>>>> has been the implicit default until now.
>>> 
>>> INT_MAX, since it then allows the maximum of open chunks. It cannot be assumed that other 1.2 devices is limited to a single open chunk.
>> So you want the default to be that all blocks on the device can be
>> opened at the same time. Interesting... I guess that such a SSD will
>> have a AA battery attached to it, but fine by me if that's how you want
>> it.
> 
> I feel you're a bit sarcastic here. One may think of SLC and other memories that does one-shot programming. In that case no caching is needed, and therefore power-caps can be limited on the hardware.

Sure. Hope people move to 2.0 then for all >SLC memories out there,
otherwise we'll see a lot of quirks coming in. Thought we wanted to be
generic.

> 
>> Assuming this, can we instead set it to the reported number of chunks,
>> since this is the hard limit anyway.
> 
> Works for me.

Cool. I'll add this to the next version.

Javier

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