linux-kernel - Re: [PATCH v10 06/22] IB/hns: Add initial cmd operation

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Message-ID: <20160622045450.GC9762@leon.nu>
Date:	Wed, 22 Jun 2016 07:54:50 +0300
From:	Leon Romanovsky <leon@...nel.org>
To:	"Wei Hu (Xavier)" <xavier.huwei@...wei.com>
Cc:	Lijun Ou <oulijun@...wei.com>, dledford@...hat.com,
	sean.hefty@...el.com, hal.rosenstock@...il.com,
	davem@...emloft.net, jeffrey.t.kirsher@...el.com,
	jiri@...lanox.com, ogerlitz@...lanox.com,
	linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, gongyangming@...wei.com,
	xiaokun@...wei.com, tangchaofei@...wei.com, haifeng.wei@...wei.com,
	yisen.zhuang@...wei.com, yankejian@...wei.com,
	charles.chenxin@...wei.com, linuxarm@...wei.com
Subject: Re: [PATCH v10 06/22] IB/hns: Add initial cmd operation

On Tue, Jun 21, 2016 at 09:01:57PM +0800, Wei Hu (Xavier) wrote:
> 
> 
> On 2016/6/21 19:28, Leon Romanovsky wrote:
> >On Tue, Jun 21, 2016 at 06:50:51PM +0800, Wei Hu (Xavier) wrote:
> >>
> >>On 2016/6/20 21:33, Leon Romanovsky wrote:
> >>>On Thu, Jun 16, 2016 at 10:35:14PM +0800, Lijun Ou wrote:
> >>>>This patch added the operation for cmd, and added some functions
> >>>>for initializing eq table and selecting cmd mode.
> >>>>
> >>>>Signed-off-by: Wei Hu <xavier.huwei@...wei.com>
> >>>>Signed-off-by: Nenglong Zhao <zhaonenglong@...ilicon.com>
> >>>>Signed-off-by: Lijun Ou <oulijun@...wei.com>
> >>>>---
> >>>>PATCH v9/v8/v7/v6:
> >>>>- No change over the PATCH v5
> >>>>
> >>>>PATCH v5:
> >>>>- The initial patch which was redesigned based on the second patch
> >>>>   in PATCH v4
> >>>>---
> >>><...>
> >>>
> >>>>+#define CMD_MAX_NUM		32
> >>>>+
> >>>>+int hns_roce_cmd_init(struct hns_roce_dev *hr_dev)
> >>>>+{
> >>>>+	struct device *dev = &hr_dev->pdev->dev;
> >>>>+
> >>>>+	mutex_init(&hr_dev->cmd.hcr_mutex);
> >>>>+	sema_init(&hr_dev->cmd.poll_sem, 1);
> >>>>+	hr_dev->cmd.use_events = 0;
> >>>>+	hr_dev->cmd.toggle = 1;
> >>>>+	hr_dev->cmd.max_cmds = CMD_MAX_NUM;
> >>><...>
> >>>
> >>>>+	for (hr_cmd->token_mask = 1; hr_cmd->token_mask < hr_cmd->max_cmds;
> >>>>+	     hr_cmd->token_mask <<= 1)
> >>>>+		;
> >>>>+	--hr_cmd->token_mask;
> >>>It doesn't look that you dynamically change max_cmds supported.
> >>>Why do you need to calculate token_mask dynamically?
> >>Hi, Leon
> >>
> >>     1. The four lines above are in the function named
> >>hns_roce_cmd_use_events.
> >>          and now this function is only called once in hns_roce_probe.
> >>     2. In hns_roce_cmd_use_events,
> >>         we use these 4 lines to achieve the value of hr_cmd->token_mask
> >>according to hr_cmd->max_cmds dynamically,
> >>         then we only define one marco for hr_cmd->max_cmds as below:
> >>
> >>	#define CMD_MAX_NUM		32
> >>
> >>        And it looks more flexible.
> >It is called over engineering.
> >I would recommend to you to remove it.
> >
> >We don't need over complicated code which is executed
> >once with need to maintain with zero benefit.
> >
> >The other places need such simplification too.
> Hi, Leon
> 
>         We will modify this place as below:
>         In hns_roce_hw_v1.c(for hip06 soc) file:
> 
>             void hns_roce_v1_profile(struct hns_roce_dev *hr_dev)
>             {
>                 <snip>
>                 caps->max_cmds = 32;
>                 <snip>
>             }
> 
>         In hns_roce_cmd.c file:
> 
>   	  int hns_roce_cmd_init(struct hns_roce_dev *hr_dev)
> 	  {
> 	     <snip>
> 	     hr_dev->cmd.max_cmds = hr_dev->caps->max_cmds;
>      		<snip>
>           }
> 
>        Can you give more suggestions?

I would be happy to do it if I had enough time to review this code.

General suggestion will be to ask yourself, if value is going to be
changed during the runtime. In case the answer is no, there is no room
to additional logic which translate constant to different value which
will be other constant.

You should do it across all the patchset.

So, in this specific case, the proposed change is not enough, you are
not solving an issue, but hiding it.

Thanks

> 
> 
> Regards
> Wei Hu
> >>Regards
> >>Wei Hu
> >>
> >>
> >>
> 
> 

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