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

Stanley Chu
2020-04-30T08:37:39Z

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