Re: [PATCH v3 2/5] nvme: add get_ams for nvme_ctrl_ops

[Minwoo Im <minwoo.im.dev@gmail.com>]

On 19-06-24 22:29:05, Weiping Zhang wrote:
> The get_ams() will return the AMS(Arbitration Mechanism Selected)
> from the driver.
> 
> Signed-off-by: Weiping Zhang <zhangweiping@didiglobal.com>

Hello, Weiping.

Sorry, but I don't really get what your point is here.  Could you please
elaborate this patch a little bit more?  The commit description just
says a function would just return the AMS from nowhere..

> ---
>  drivers/nvme/host/core.c | 9 ++++++++-
>  drivers/nvme/host/nvme.h | 1 +
>  drivers/nvme/host/pci.c  | 6 ++++++
>  include/linux/nvme.h     | 1 +
>  4 files changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index b2dd4e391f5c..4cb781e73123 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -1943,6 +1943,7 @@ int nvme_enable_ctrl(struct nvme_ctrl *ctrl, u64 cap)
>  	 */
>  	unsigned dev_page_min = NVME_CAP_MPSMIN(cap) + 12, page_shift = 12;
>  	int ret;
> +	u32 ams = NVME_CC_AMS_RR;
>  
>  	if (page_shift < dev_page_min) {
>  		dev_err(ctrl->device,
> @@ -1951,11 +1952,17 @@ int nvme_enable_ctrl(struct nvme_ctrl *ctrl, u64 cap)
>  		return -ENODEV;
>  	}
>  
> +	/* get Arbitration Mechanism Selected */
> +	if (ctrl->ops->get_ams) {

I just wonder if this check will be valid because this patch just
register the function nvme_pci_get_ams() without any conditions.

> +		ctrl->ops->get_ams(ctrl, &ams);
> +		ams &= NVME_CC_AMS_MASK;
> +	}
> +
>  	ctrl->page_size = 1 << page_shift;
>  
>  	ctrl->ctrl_config = NVME_CC_CSS_NVM;
>  	ctrl->ctrl_config |= (page_shift - 12) << NVME_CC_MPS_SHIFT;
> -	ctrl->ctrl_config |= NVME_CC_AMS_RR | NVME_CC_SHN_NONE;
> +	ctrl->ctrl_config |= ams | NVME_CC_SHN_NONE;
>  	ctrl->ctrl_config |= NVME_CC_IOSQES | NVME_CC_IOCQES;
>  	ctrl->ctrl_config |= NVME_CC_ENABLE;
>  
> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
> index ea45d7d393ad..9c7e9217f78b 100644
> --- a/drivers/nvme/host/nvme.h
> +++ b/drivers/nvme/host/nvme.h
> @@ -369,6 +369,7 @@ struct nvme_ctrl_ops {
>  	void (*submit_async_event)(struct nvme_ctrl *ctrl);
>  	void (*delete_ctrl)(struct nvme_ctrl *ctrl);
>  	int (*get_address)(struct nvme_ctrl *ctrl, char *buf, int size);
> +	void (*get_ams)(struct nvme_ctrl *ctrl, u32 *ams);

Can we just have a return value for the AMS value?

>  };
>  
>  #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> index 189352081994..5d84241f0214 100644
> --- a/drivers/nvme/host/pci.c
> +++ b/drivers/nvme/host/pci.c
> @@ -2627,6 +2627,11 @@ static int nvme_pci_get_address(struct nvme_ctrl *ctrl, char *buf, int size)
>  	return snprintf(buf, size, "%s", dev_name(&pdev->dev));
>  }
>  
> +static void nvme_pci_get_ams(struct nvme_ctrl *ctrl, u32 *ams)
> +{
> +	*ams = NVME_CC_AMS_RR;
> +}
> +
>  static const struct nvme_ctrl_ops nvme_pci_ctrl_ops = {
>  	.name			= "pcie",
>  	.module			= THIS_MODULE,
> @@ -2638,6 +2643,7 @@ static const struct nvme_ctrl_ops nvme_pci_ctrl_ops = {
>  	.free_ctrl		= nvme_pci_free_ctrl,
>  	.submit_async_event	= nvme_pci_submit_async_event,
>  	.get_address		= nvme_pci_get_address,
> +	.get_ams		= nvme_pci_get_ams,

Question: Do we really need this being added to nvme_ctrl_ops?

Also If 5th patch will make this function much more than this, then it
would be great if you describe this kind of situation in description :)

>  };
>  
>  static int nvme_dev_map(struct nvme_dev *dev)
> diff --git a/include/linux/nvme.h b/include/linux/nvme.h
> index da5f696aec00..8f71451fc2fa 100644
> --- a/include/linux/nvme.h
> +++ b/include/linux/nvme.h
> @@ -156,6 +156,7 @@ enum {
>  	NVME_CC_AMS_RR		= 0 << NVME_CC_AMS_SHIFT,
>  	NVME_CC_AMS_WRRU	= 1 << NVME_CC_AMS_SHIFT,
>  	NVME_CC_AMS_VS		= 7 << NVME_CC_AMS_SHIFT,
> +	NVME_CC_AMS_MASK	= 7 << NVME_CC_AMS_SHIFT,
>  	NVME_CC_SHN_NONE	= 0 << NVME_CC_SHN_SHIFT,
>  	NVME_CC_SHN_NORMAL	= 1 << NVME_CC_SHN_SHIFT,
>  	NVME_CC_SHN_ABRUPT	= 2 << NVME_CC_SHN_SHIFT,
> -- 
> 2.14.1
>