linux-kernel - RE:(2) [PATCH v4 4/7] scsi: ufs: wb: Add explicit flush sysfs attribute

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Date:   Thu, 28 Jul 2022 09:54:03 +0900
From:   Jinyoung CHOI <j-young.choi@...sung.com>
To:     ALIM AKHTAR <alim.akhtar@...sung.com>,
        "avri.altman@....com" <avri.altman@....com>,
        "bvanassche@....org" <bvanassche@....org>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "beanhuo@...ron.com" <beanhuo@...ron.com>,
        "adrian.hunter@...el.com" <adrian.hunter@...el.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE:(2) [PATCH v4 4/7] scsi: ufs: wb: Add explicit flush sysfs
 attribute

>> There is the following quirk to bypass "WB Flush" in Write Booster.
>> 
>>         - UFSHCI_QUIRK_SKIP_MANUAL_WB_FLUSH_CTRL
>> 
>> If this quirk is not set, there is no knob that can control "WB
>> Flush".
>
>> 
>> There are three flags that control Write Booster Feature.
>>         1. WB ON/OFF
>>         2. WB Hibern Flush ON/OFF (implicitly)
>>         3. WB Flush ON/OFF (explicit)
>> 
>> The sysfs attribute that controls the WB was implemented. (1)
>> 
>> In the case of "Hibern Flush", it is always good to turn on.
>> Control may not be required. (2)
>> 
>> Finally, "Flush" may be necessary because the Auto-Hibern8 is not
>> supported in a specific environment.
>> So the sysfs attribute that controls this is necessary. (3)
>> 
>> Reviewed-by: Avri Altman <avri.altman@....com>
>> Signed-off-by: Jinyoung Choi <j-young.choi@...sung.com>
>> ---
>...
>> 
>> +static ssize_t wb_buf_flush_en_store(struct device *dev,
>> +                                    struct device_attribute *attr,
>> +                                    const char *buf, size_t count)
>> +{
>> +       struct ufs_hba *hba = dev_get_drvdata(dev);
>> +       unsigned int wb_buf_flush_en;
>> +       ssize_t res;
>> +
>> +       if (ufshcd_is_wb_allowed(hba) &&
>> +          !(hba->quirks & UFSHCI_QUIRK_SKIP_MANUAL_WB_FLUSH_CTRL)) {
>> +               dev_warn(dev, "It is not allowed to configure WB buf
>> flush!\n");
>> +               return -EOPNOTSUPP;
>> +       }
>> +
>Hi J-young,
>
>I don't understand here, if UFSHCI_QUIRK_SKIP_MANUAL_WB_FLUSH_CTRL is
>not set (manual flush is not disable), so we cannot manually flush
>buffer? or should we check if Auto-Hibern8 is supported?
>
>Kind regards,
>Bean

Hi Bean, 
As the patch was separated, the conditional sentence went wrong.
Thank you for checking. I will modify it quickly.

Thanks,
Jinyoung.