scsi: ufs: Introduce skipping manual flush for Write Booster

We have two knobs to control flush for write booster,
fWriteBoosterBufferFlushDuringHibernate and fWriteBoosterBufferFlushEn.

Some vendors use only fWriteBoosterBufferFlushDuringHibernate because this
can reportedly cover most scenarios. Also, there have been some reports
that flush by fWriteBoosterBufferFlushEn could lead to increased power
consumption thanks to unexpected internal operations. Consequently, we need
a way to enable or disable fWriteBoosterEn operations. Add quirk to bypass
manual flush.

Link: https://lore.kernel.org/r/ffdb0eda30515809f0ad9ee936b26917ee9b4593.1598319701.git.kwmad.kim@samsung.comReviewed-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Kiwoong Kim <kwmad.kim@samsung.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ufs/ufshcd.c

@@ -5306,6 +5306,9 @@ static int ufshcd_wb_toggle_flush_during_h8(struct ufs_hba *hba, bool set)
 
 static inline void ufshcd_wb_toggle_flush(struct ufs_hba *hba, bool enable)
 {
+	if (hba->quirks & UFSHCI_QUIRK_SKIP_MANUAL_WB_FLUSH_CTRL)
+		return;
+
 	if (enable)
 		ufshcd_wb_buf_flush_enable(hba);
 	else

drivers/scsi/ufs/ufshcd.h

@@ -530,6 +530,11 @@ enum ufshcd_quirks {
 	 * OCS FATAL ERROR with device error through sense data
 	 */
 	UFSHCD_QUIRK_BROKEN_OCS_FATAL_ERROR		= 1 << 10,
+
+	/*
+	 * This quirk needs to disable manual flush for write booster
+	 */
+	UFSHCI_QUIRK_SKIP_MANUAL_WB_FLUSH_CTRL		= 1 << 11,
 };
 
 enum ufshcd_caps {