linux-kernel - Re: [PATCH v2 3/3] scsi: ufs: core: Add sysfs attributes to control WB buffer resize function

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Message-ID: <d5e3a6e6-882d-4f75-8eef-5f3e1058f921@acm.org>
Date:   Fri, 8 Sep 2023 08:43:58 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Lu Hongfei <luhongfei@...o.com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Can Guo <quic_cang@...cinc.com>, Bean Huo <beanhuo@...ron.com>,
        Arthur Simchaev <arthur.simchaev@....com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Asutosh Das <quic_asutoshd@...cinc.com>,
        "Bao D. Nguyen" <quic_nguyenb@...cinc.com>,
        zhanghui <zhanghui31@...omi.com>,
        Po-Wen Kao <powen.kao@...iatek.com>,
        Eric Biggers <ebiggers@...gle.com>,
        Keoseong Park <keosung.park@...sung.com>,
        linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org
Cc:     opensource.kernel@...o.com
Subject: Re: [PATCH v2 3/3] scsi: ufs: core: Add sysfs attributes to control
 WB buffer resize function

> +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@...o.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.