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Message-ID: <d5e3a6e6-882d-4f75-8eef-5f3e1058f921@acm.org>
Date:   Fri, 8 Sep 2023 08:43:58 -0700
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v2 3/3] scsi: ufs: core: Add sysfs attributes to control
 WB buffer resize function
Content-Language: en-US
To:     Lu Hongfei <luhongfei@vivo.com>,
        Alim Akhtar <alim.akhtar@samsung.com>,
        Avri Altman <avri.altman@wdc.com>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Can Guo <quic_cang@quicinc.com>, Bean Huo <beanhuo@micron.com>,
        Arthur Simchaev <arthur.simchaev@wdc.com>,
        Stanley Chu <stanley.chu@mediatek.com>,
        Manivannan Sadhasivam <mani@kernel.org>,
        Asutosh Das <quic_asutoshd@quicinc.com>,
        "Bao D. Nguyen" <quic_nguyenb@quicinc.com>,
        zhanghui <zhanghui31@xiaomi.com>,
        Po-Wen Kao <powen.kao@mediatek.com>,
        Eric Biggers <ebiggers@google.com>,
        Keoseong Park <keosung.park@samsung.com>,
        linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org
Cc:     opensource.kernel@vivo.com
References: <20230908102113.547-1-luhongfei@vivo.com>
 <20230908102113.547-4-luhongfei@vivo.com>
From:   Bart Van Assche <bvanassche@acm.org>
In-Reply-To: <20230908102113.547-4-luhongfei@vivo.com>
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> +What:		/sys/bus/platform/drivers/ufshcd/*/enable_wb_buf_resize
> +What:		/sys/bus/platform/devices/*.ufs/enable_wb_buf_resize
> +Date:		Sept 2023
> +Contact:	Lu Hongfei <luhongfei@vivo.com>
> +Description:
> +		The host can decrease or increase the WriteBooster Buffer size by setting
> +		this file.
> +
> +		======  ======================================
> +		   00h  Idle (There is no resize operation)
> +		   01h  Decrease WriteBooster Buffer Size
> +		   02h  Increase WriteBooster Buffer Size
> +		Others  Reserved
> +		======  ======================================
> +
> +		The file is write only.

The name "enable_wb_buf_resize" seems misleading to me. 
"wb_buf_resize_control" is probably a better name for this attribute 
since this attribute can be used to increase and decrease the WB buffer 
size.

> +	if (hba->dev_info.wspecversion < 0x410 ||
> +	    !hba->dev_info.b_presrv_uspc_en) {
> +		dev_err(dev, "The WB buf resize is not allowed!\n");
> +		return -EINVAL;
> +	}

Please leave out the version number check. There probably will be UFS 
4.0 devices that will implement this feature.

Thanks,

Bart.