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

[Matias BjÃrling]

On 02/22/2018 10:52 AM, Javier Gonzalez wrote:
> > On 22 Feb 2018, at 10.45, Matias BjÃrling <mb@xxxxxxxxxxx> wrote:
> >
> > On 02/22/2018 08:55 AM, Javier Gonzalez wrote:
> > > > On 22 Feb 2018, at 08.45, Matias BjÃrling <mb@xxxxxxxxxxx> wrote:
> > > >
> > > > On 02/21/2018 10:26 AM, Javier GonzÃlez wrote:
> > > > > Complete the generic geometry structure with the maxoc and maxocpu
> > > > > felds, present in the 2.0 spec.
> > > > > Signed-off-by: Javier GonzÃlez <javier@xxxxxxxxxxxx>
> > > > > ---
> > > > >   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.

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

Works for me.