RE: [EXT] [PATCH v6 6/8] scsi: ufs: add LU Dedicated buffer mode support for WriteBooster

[Bean Huo (beanhuo)]

> From: Stanley Chu <stanley.chu@xxxxxxxxxxxx>
> Sent: Monday, May 4, 2020 4:56 PM
> To: linux-scsi@xxxxxxxxxxxxxxx; martin.petersen@xxxxxxxxxx;
> avri.altman@xxxxxxx; alim.akhtar@xxxxxxxxxxx; jejb@xxxxxxxxxxxxx;
> asutoshd@xxxxxxxxxxxxxx
> Cc: Bean Huo (beanhuo) <beanhuo@xxxxxxxxxx>; cang@xxxxxxxxxxxxxx;
> matthias.bgg@xxxxxxxxx; bvanassche@xxxxxxx; linux-
> mediatek@xxxxxxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; kuohong.wang@xxxxxxxxxxxx;
> peter.wang@xxxxxxxxxxxx; chun-hung.wu@xxxxxxxxxxxx;
> andy.teng@xxxxxxxxxxxx; Stanley Chu <stanley.chu@xxxxxxxxxxxx>
> Subject: [EXT] [PATCH v6 6/8] scsi: ufs: add LU Dedicated buffer mode support
> for WriteBooster
> 
> According to UFS specification, there are two WriteBooster mode of
> operations: "LU dedicated buffer" mode and "shared buffer" mode.
> In the "LU dedicated buffer" mode, the WriteBooster Buffer is dedicated to a
> logical unit.
> 
> If the device supports the "LU dedicated buffer" mode, this mode is configured
> by setting bWriteBoosterBufferType to 00h. The logical unit WriteBooster Buffer
> size is configured by setting the dLUNumWriteBoosterBufferAllocUnits field of
> the related Unit Descriptor. Only a value greater than zero enables the
> WriteBooster feature in the logical unit.
> 
> Modify ufshcd_wb_probe() as above description to support LU Dedicated buffer
> mode.
> 
> Note that according to UFS 3.1 specification, the valid value of
> bDeviceMaxWriteBoosterLUs parameter in Geometry Descriptor is 1, which
> means at most one LUN can have WriteBooster buffer in "LU dedicated buffer
> mode". Therefore this patch supports only one LUN with WriteBooster enabled.
> All WriteBooster related sysfs nodes are specifically mapped to the LUN with
> WriteBooster enabled in LU Dedicated buffer mode.
> 
> Signed-off-by: Stanley Chu <stanley.chu@xxxxxxxxxxxx>
> Reviewed-by: Avri Altman <avri.altman@xxxxxxx>
Reviewed-by: Bean Huo <beanhuo@xxxxxxxxxx>