disp: msm: sde: avoid using spinlock for register log

Add support to use atomic variable instead of spinlock
for register logs during register write. This change
helps in reducing the run-time and is safe to use as
most of the register writes happen in commit context.

Change-Id: Ib7e377f80cbf437e391792b0b424cbd1eefdf497
Signed-off-by: Yashwanth <yvulapu@codeaurora.org>
Signed-off-by: Samantha Tran <samtran@codeaurora.org>

msm/sde_dbg_evtlog.c

@@ -103,27 +103,22 @@ exit:
 
 void sde_reglog_log(u8 blk_id, u32 val, u32 addr)
 {
-	unsigned long flags;
 	struct sde_dbg_reglog_log *log;
 	struct sde_dbg_reglog *reglog = sde_dbg_base_reglog;
+	int index;
 
 	if (!reglog)
 		return;
 
-	spin_lock_irqsave(&reglog->spin_lock, flags);
-
-	log = &reglog->logs[reglog->curr];
+	index = abs(atomic64_inc_return(&reglog->curr) % SDE_REGLOG_ENTRY);
 
+	log = &reglog->logs[index];
 	log->blk_id = blk_id;
 	log->val = val;
 	log->addr = addr;
 	log->time = local_clock();
 	log->pid = current->pid;
-
-	reglog->curr = (reglog->curr + 1) % SDE_REGLOG_ENTRY;
 	reglog->last++;
-
-	spin_unlock_irqrestore(&reglog->spin_lock, flags);
 }
 
 /* always dump the last entries which are not dumped yet */
@@ -245,7 +240,7 @@ struct sde_dbg_reglog *sde_reglog_init(void)
 	if (!reglog)
 		return ERR_PTR(-ENOMEM);
 
-	spin_lock_init(&reglog->spin_lock);
+	atomic64_set(&reglog->curr, 0);
 
 	return reglog;
 }