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

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Message-ID: <576A352F.8000700@huawei.com>
Date:	Wed, 22 Jun 2016 14:50:23 +0800
From:	"Wei Hu (Xavier)" <xavier.huwei@...wei.com>
To:	<leon@...nel.org>
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 2016/6/22 12:54, Leon Romanovsky wrote:
> 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
We will modify this place as below：

     #define CMD_TOKEN_MASK      0x1f

    hr_cmd->token_mask = CMD_TOKEN_MASK;

    delete these four lines:

	for (hr_cmd->token_mask = 1; hr_cmd->token_mask < hr_cmd->max_cmds;
	     hr_cmd->token_mask <<= 1)
		;
	--hr_cmd->token_mask;

  	
Thanks

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