linux-kernel - RE: [PATCH v2 3/5] scsi: ufs: add LU Dedicated buffer mode support for WriteBooster

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Date:   Thu, 30 Apr 2020 16:37:33 +0800
From:   Stanley Chu <stanley.chu@...iatek.com>
To:     Avri Altman <Avri.Altman@....com>
CC:     "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "alim.akhtar@...sung.com" <alim.akhtar@...sung.com>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        "beanhuo@...ron.com" <beanhuo@...ron.com>,
        "cang@...eaurora.org" <cang@...eaurora.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "bvanassche@....org" <bvanassche@....org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kuohong.wang@...iatek.com" <kuohong.wang@...iatek.com>,
        "peter.wang@...iatek.com" <peter.wang@...iatek.com>,
        "chun-hung.wu@...iatek.com" <chun-hung.wu@...iatek.com>,
        "andy.teng@...iatek.com" <andy.teng@...iatek.com>
Subject: RE: [PATCH v2 3/5] scsi: ufs: add LU Dedicated buffer mode support
 for WriteBooster

Hi Avri,

On Thu, 2020-04-30 at 08:30 +0000, Avri Altman wrote:
> > 
> >  static void ufshcd_wb_probe(struct ufs_hba *hba, u8 *desc_buf)
> >  {
> > +       int ret;
> > +       u8 lun;
> > +       u32 d_lu_wb_buf_alloc = 0;
> > +
> >         if (hba->desc_size.dev_desc <=
> > DEVICE_DESC_PARAM_EXT_UFS_FEATURE_SUP)
> >                 goto wb_disabled;
> > 
> > @@ -6821,15 +6842,35 @@ static void ufshcd_wb_probe(struct ufs_hba
> > *hba, u8 *desc_buf)
> >         hba->dev_info.b_wb_buffer_type =
> >                 desc_buf[DEVICE_DESC_PARAM_WB_TYPE];
> > 
> > -       hba->dev_info.d_wb_alloc_units =
> > -               get_unaligned_be32(desc_buf +
> > -                                  DEVICE_DESC_PARAM_WB_SHARED_ALLOC_UNITS);
> >         hba->dev_info.b_presrv_uspc_en =
> >                 desc_buf[DEVICE_DESC_PARAM_WB_PRESRV_USRSPC_EN];
> > 
> > -       if (!(hba->dev_info.b_wb_buffer_type &&
> > -             hba->dev_info.d_wb_alloc_units))
> > -               goto wb_disabled;
> > +       if (hba->dev_info.b_wb_buffer_type == WB_BUF_MODE_SHARED) {
> > +               hba->dev_info.d_wb_alloc_units =
> > +               get_unaligned_be32(desc_buf +
> > +                                  DEVICE_DESC_PARAM_WB_SHARED_ALLOC_UNITS);
> > +               if (!hba->dev_info.d_wb_alloc_units)
> > +                       goto wb_disabled;
> > +       } else {
> > +               for (lun = 0; lun < hba->dev_info.max_lu_supported; lun++) {
> > +                       ret = ufshcd_read_unit_desc_param(hba,
> > +                                       lun,
> > +                                       UNIT_DESC_PARAM_WB_BUF_ALLOC_UNITS,
> > +                                       (u8 *)&d_lu_wb_buf_alloc,
> > +                                       sizeof(d_lu_wb_buf_alloc));
> > +                       if (ret)
> > +                               goto wb_disabled;
> > +                       if (d_lu_wb_buf_alloc) {
> > +                               hba->dev_info.wb_dedicated_lu = lun;
> > +                               break;
> Why are you allowing only a single WB lun?
> You should allow those buffers for lun0..lun7

In UFS 3.1 specification, the valid value of bDeviceMaxWriteBoosterLUs
is 1. Therefore only one LU can have WriteBooster buffer.

Thanks,
Stanley