scsi: ufs: introduce common and flexible delay function

Introduce a common delay function to provide flexible way for users to take
choices of udelay and usleep_range into consideration according to the
required delay time.

Link: https://lore.kernel.org/r/20200318104016.28049-4-stanley.chu@mediatek.comReviewed-by: Avri Altman <avri.altman@wdc.com>
Reviewed-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ufs/ufshcd.c

@@ -535,6 +535,18 @@ static void ufshcd_print_pwr_info(struct ufs_hba *hba)
 		 hba->pwr_info.hs_rate);
 }
 
+void ufshcd_delay_us(unsigned long us, unsigned long tolerance)
+{
+	if (!us)
+		return;
+
+	if (us < 10)
+		udelay(us);
+	else
+		usleep_range(us, us + tolerance);
+}
+EXPORT_SYMBOL_GPL(ufshcd_delay_us);
+
 /*
  * ufshcd_wait_for_register - wait for register value to change
  * @hba - per-adapter interface

drivers/scsi/ufs/ufshcd.h

@@ -797,6 +797,7 @@ int ufshcd_init(struct ufs_hba * , void __iomem * , unsigned int);
 int ufshcd_make_hba_operational(struct ufs_hba *hba);
 void ufshcd_remove(struct ufs_hba *);
 int ufshcd_uic_hibern8_exit(struct ufs_hba *hba);
+void ufshcd_delay_us(unsigned long us, unsigned long tolerance);
 int ufshcd_wait_for_register(struct ufs_hba *hba, u32 reg, u32 mask,
 				u32 val, unsigned long interval_us,
 				unsigned long timeout_ms, bool can_sleep);