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Subject: Re: [<RFC PATCH v1> 1/2] scsi: ufs: add write booster feature support
To:     Avri Altman <Avri.Altman@wdc.com>,
        "subhashj@codeaurora.org" <subhashj@codeaurora.org>,
        "cang@codeaurora.org" <cang@codeaurora.org>,
        "rnayak@codeaurora.org" <rnayak@codeaurora.org>,
        "vinholikatti@gmail.com" <vinholikatti@gmail.com>,
        "jejb@linux.vnet.ibm.com" <jejb@linux.vnet.ibm.com>,
        "martin.petersen@oracle.com" <martin.petersen@oracle.com>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>
Cc:     "linux-arm-msm@vger.kernel.org" <linux-arm-msm@vger.kernel.org>,
        Alim Akhtar <alim.akhtar@samsung.com>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        Stanley Chu <stanley.chu@mediatek.com>,
        Bean Huo <beanhuo@micron.com>,
        Tomas Winkler <tomas.winkler@intel.com>,
        Colin Ian King <colin.king@canonical.com>,
        Bart Van Assche <bvanassche@acm.org>,
        Venkat Gopalakrishnan <venkatg@codeaurora.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        open list <linux-kernel@vger.kernel.org>
References: <cover.1582330473.git.asutoshd@codeaurora.org>
 <0eb182e6731bc4ce0c1d6a97f102155d7186520f.1582330473.git.asutoshd@codeaurora.org>
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From:   "Asutosh Das (asd)" <asutoshd@codeaurora.org>
Message-ID: <54fd84a6-0c20-ba96-c9a6-5c76bf2611c7@codeaurora.org>
Date:   Wed, 26 Feb 2020 09:57:00 -0800
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On 2/25/2020 4:50 AM, Avri Altman wrote:
>> +/*
>> + * ufshcd_get_wb_alloc_units - returns
>> "dLUNumWriteBoosterBufferAllocUnits"
>> + * @hba: per-adapter instance
>> + * @lun: UFS device lun id
>> + * @d_lun_wbb_au: pointer to buffer to hold the LU's alloc units info
>> + *
>> + * Returns 0 in case of success and d_lun_wbb_au would be returned
>> + * Returns -ENOTSUPP if reading d_lun_wbb_au is not supported.
>> + * Returns -EINVAL in case of invalid parameters passed to this function.
>> + */
>> +static int ufshcd_get_wb_alloc_units(struct ufs_hba *hba,
>> +                           u8 lun,
>> +                           u8 *d_lun_wbb_au)
>> +{
>> +       int ret;
>> +
>> +       if (!d_lun_wbb_au)
>> +               ret = -EINVAL;
>> +
>> +       /* WB can be supported only from LU0..LU7 */
>> +       else if (lun >= UFS_UPIU_MAX_GENERAL_LUN)
>> +               ret = -ENOTSUPP;
>> +       else
>> +               ret = ufshcd_read_unit_desc_param(hba,
>> +                                         lun,
>> +                                         UNIT_DESC_PARAM_WB_BUF_ALLOC_UNITS,
>> +                                         d_lun_wbb_au,
>> +                                         sizeof(*d_lun_wbb_au));
> You are reading here a single byte, instead of 4
> 
>> +       return ret;
>> +}
>> +
>>   /**
>>    * ufshcd_get_lu_power_on_wp_status - get LU's power on write protect
>>    * status
>> @@ -5194,6 +5267,165 @@ static void
>> ufshcd_bkops_exception_event_handler(struct ufs_hba *hba)
>>                                  __func__, err);
>>   }
>>
>> +static bool ufshcd_wb_sup(struct ufs_hba *hba)
>> +{
>> +       return ((hba->dev_info.d_ext_ufs_feature_sup &
>> +                  UFS_DEV_WRITE_BOOSTER_SUP) &&
> Don't you want to have a vendor cap as well,
> to allow the platform vendor to control this feature?
> 
>> +                 (hba->dev_info.b_wb_buffer_type
>> +                  || hba->dev_info.wb_config_lun));
>> +}
>> +
>> +
> 
> 
> 
>> +static bool ufshcd_wb_is_buf_flush_needed(struct ufs_hba *hba)
>> +{
>> +       int ret;
>> +       u32 cur_buf, status, avail_buf;
>> +
>> +       if (!ufshcd_wb_sup(hba))
>> +               return false;
>> +
>> +       ret = ufshcd_query_attr_retry(hba,
>> UPIU_QUERY_OPCODE_READ_ATTR,
>> +                                     QUERY_ATTR_IDN_AVAIL_WB_BUFF_SIZE,
>> +                                     0, 0, &avail_buf);
>> +       if (ret) {
>> +               dev_warn(hba->dev, "%s dAvailableWriteBoosterBufferSize read
>> failed %d\n",
>> +                        __func__, ret);
>> +               return false;
>> +       }
>> +
>> +       ret = ufshcd_vops_get_user_cap_mode(hba);
>> +       if (ret <= 0) {
>> +               dev_dbg(hba->dev, "Get user-cap reduction mode: failed: %d\n",
>> +                       ret);
>> +               /* Most commonly used */
>> +               ret = UFS_WB_BUFF_PRESERVE_USER_SPACE;
>> +       }
>> +
>> +       hba->dev_info.keep_vcc_on = false;
>> +       if (ret == UFS_WB_BUFF_USER_SPACE_RED_EN) {
>> +               if (avail_buf <= UFS_WB_10_PERCENT_BUF_REMAIN) {
>> +                       hba->dev_info.keep_vcc_on = true;
>> +                       return true;
>> +               }
>> +               return false;
>> +       } else if (ret == UFS_WB_BUFF_PRESERVE_USER_SPACE) {
>> +               ret = ufshcd_query_attr_retry(hba,
>> UPIU_QUERY_OPCODE_READ_ATTR,
>> +                                             QUERY_ATTR_IDN_CURR_WB_BUFF_SIZE,
>> +                                             0, 0, &cur_buf);
>> +               if (ret) {
>> +                       dev_err(hba->dev, "%s dCurWriteBoosterBufferSize read failed
>> %d\n",
>> +                                __func__, ret);
>> +                       return false;
>> +               }
>> +
>> +               if (!cur_buf) {
>> +                       dev_info(hba->dev, "dCurWBBuf: %d WB disabled until free-
>> space is available\n",
>> +                                cur_buf);
>> +                       return false;
>> +               }
>> +
>> +               ret = ufshcd_get_ee_status(hba, &status);
>> +               if (ret) {
>> +                       dev_err(hba->dev, "%s: failed to get exception status %d\n",
>> +                               __func__, ret);
>> +                       if (avail_buf < UFS_WB_40_PERCENT_BUF_REMAIN) {
>> +                               hba->dev_info.keep_vcc_on = true;
>> +                               return true;
>> +                       }
>> +                       return false;
>> +               }
>> +
>> +               status &= hba->ee_ctrl_mask;
>> +
>> +               if ((status & MASK_EE_URGENT_BKOPS) ||
> So you are getting the status, but not the bkops level.
> And what about WRITEBOOSTER_EVENT_EN? After all it was invented specifically for WB...
> 
>> +                   (avail_buf < UFS_WB_40_PERCENT_BUF_REMAIN)) {
>> +                       hba->dev_info.keep_vcc_on = true;
>> +                       return true;
>> +               }
>> +       }
>> +       return false;
>> +}
> 
> Thanks,
> Avri
> 

Thanks Avri/Bart for the comments.
I'll wait for a couple of more days, if anyone else has any comments.

I'd respond/address the comments thereafter.

Thanks,
asd

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