linux-kernel - Re: [PATCH] lightnvm: calculate device values correctly

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Date:	Sun, 22 Nov 2015 19:34:04 +0100
From:	Matias <mb@...htnvm.io>
To:	Wenwei Tao <ww.tao0320@...il.com>
CC:	linux-kernel@...r.kernel.org, linux-block@...r.kernel.org
Subject: Re: [PATCH] lightnvm:  calculate device values correctly

On 11/22/2015 02:51 PM, Wenwei Tao wrote:
> In the original calculation, the relationships among
> block, plane and lun was confusing, refine it on the
> basis of Open-channelSSDInterfaceSpecification.
>
> Signed-off-by: Wenwei Tao <ww.tao0320@...il.com>
> ---
>   drivers/lightnvm/core.c | 9 ++++-----
>   1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/lightnvm/core.c b/drivers/lightnvm/core.c
> index f659e60..1864b94 100644
> --- a/drivers/lightnvm/core.c
> +++ b/drivers/lightnvm/core.c
> @@ -174,8 +174,8 @@ static int nvm_core_init(struct nvm_dev *dev)
>   	dev->nr_chnls = grp->num_ch;
>   	dev->luns_per_chnl = grp->num_lun;
>   	dev->pgs_per_blk = grp->num_pg;
> -	dev->blks_per_lun = grp->num_blk;
>   	dev->nr_planes = grp->num_pln;
> +	dev->blks_per_lun = grp->num_blk * grp->num_pln;
>   	dev->sec_size = grp->csecs;
>   	dev->oob_size = grp->sos;
>   	dev->sec_per_pg = grp->fpg_sz / grp->csecs;
> @@ -191,13 +191,12 @@ static int nvm_core_init(struct nvm_dev *dev)
>   		dev->plane_mode = NVM_PLANE_QUAD;
>
>   	/* calculated values */
> -	dev->sec_per_pl = dev->sec_per_pg * dev->nr_planes;
> -	dev->sec_per_blk = dev->sec_per_pl * dev->pgs_per_blk;
> +	dev->sec_per_blk = dev->sec_per_pg * dev->pgs_per_blk;
> +	dev->sec_per_pl = dev->sec_per_blk * grp->num_blk;
>   	dev->sec_per_lun = dev->sec_per_blk * dev->blks_per_lun;
>   	dev->nr_luns = dev->luns_per_chnl * dev->nr_chnls;
>
> -	dev->total_blocks = dev->nr_planes *
> -				dev->blks_per_lun *
> +	dev->total_blocks = dev->blks_per_lun *
>   				dev->luns_per_chnl *
>   				dev->nr_chnls;
>   	dev->total_pages = dev->total_blocks * dev->pgs_per_blk;
>

The reason I had it as before, was because I wanted to drive the device 
in either single/double/quad read/write/erase plane mode. That way we 
could get away with only managing 1/4 or 1/2 of the block metadata.

What is your use case? It could make sense, but it will require a little 
more work to build up the framework for having the various modes. i.e. 
detect supported plane mode, make a explicit decision about which plane 
mode to always use (or dynamically) and afterwards allocate the 
appropriate data structures.
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