[PATCH] NVMe: Fix START_STOP_UNIT Scsi->NVMe translation.

[Verma, Vishal L]

On Fri, 2014-06-06 at 08:27 -0600, Dan McLeran wrote:
> This patch contains several fixes for Scsi START_STOP_UNIT. The previous code did not account for
> signed vs. unsigned arithmetic which resulted in an invalid lowest power state caculation when
> the device only supports 1 power state.
> 
> The code for Power Condition == 2 (Idle) was not following the spec. The spec calls out
> setting the device to specific power states, depending upon Power Condition Modifier, without
> accounting for the number of power states supported by the device.
> 
> The code for Power Condition == 3 (Standby) was using a hard-coded '0' which I replaced with the
> macro POWER_STATE_0.
> 
> Signed-off-by: Dan McLeran <daniel.mcleran at intel.com>
> ---
>  drivers/block/nvme-scsi.c |   12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 

Looks good.
Reviewed-by: Vishal Verma <vishal.l.verma at linux.intel.com>


> diff --git a/drivers/block/nvme-scsi.c b/drivers/block/nvme-scsi.c
> index 4fc25b9..61215ca 100644
> --- a/drivers/block/nvme-scsi.c
> +++ b/drivers/block/nvme-scsi.c
> @@ -1477,7 +1477,7 @@ static int nvme_trans_power_state(struct nvme_ns *ns, struct sg_io_hdr *hdr,
>  		goto out_dma;
>  	}
>  	id_ctrl = mem;
> -	lowest_pow_st = id_ctrl->npss - 1;
> +	lowest_pow_st = max(POWER_STATE_0, (int)(id_ctrl->npss - 1));
>  
>  	switch (pc) {
>  	case NVME_POWER_STATE_START_VALID:
> @@ -1496,18 +1496,18 @@ static int nvme_trans_power_state(struct nvme_ns *ns, struct sg_io_hdr *hdr,
>  		/* Action unspecified if POWER CONDITION MODIFIER != [0,1,2] */
>  		/* min of desired state and (lps-1) because lps is STOP */
>  		if (pcmod == 0x0)
> -			ps_desired = min(POWER_STATE_1, (lowest_pow_st - 1));
> +			ps_desired = POWER_STATE_1;
>  		else if (pcmod == 0x1)
> -			ps_desired = min(POWER_STATE_2, (lowest_pow_st - 1));
> +			ps_desired = POWER_STATE_2;
>  		else if (pcmod == 0x2)
> -			ps_desired = min(POWER_STATE_3, (lowest_pow_st - 1));
> +			ps_desired = POWER_STATE_3;
>  		break;
>  	case NVME_POWER_STATE_STANDBY:
>  		/* Action unspecified if POWER CONDITION MODIFIER != [0,1] */
>  		if (pcmod == 0x0)
> -			ps_desired = max(0, (lowest_pow_st - 2));
> +			ps_desired = max(POWER_STATE_0, (lowest_pow_st - 2));
>  		else if (pcmod == 0x1)
> -			ps_desired = max(0, (lowest_pow_st - 1));
> +			ps_desired = max(POWER_STATE_0, (lowest_pow_st - 1));
>  		break;
>  	case NVME_POWER_STATE_LU_CONTROL:
>  	default: