linux-kernel - [PATCH] rtc: msm6242: Remove unneeded msm6242_set()/msm6242

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Date:   Sat, 16 Nov 2019 12:46:20 +0100
From:   Kars de Jong <jongk@...ux-m68k.org>
To:     Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     linux-rtc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kars de Jong <jongk@...ux-m68k.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: [PATCH] rtc: msm6242: Remove unneeded msm6242_set()/msm6242_clear() functions

The msm6242_set()/msm6242_clear() functions are used when writing to Control
Register D to set or clear the HOLD bit when reading the current time from
the RTC.

Doing this with a read-modify-write cycle will potentially clear an
interrupt condition which occurs between the read and the write.

The datasheet states the following about this:

  When writing the HOLD or 30 second adjust bits of register D, it is
  necessary to write the IRQ FLAG bit to a "1".

Since the only other bits in the register are the 30 second adjust bit
(which is not used) and the BUSY bit (which is read-only), the
read-modify-write cycle can be replaced by a simple write with the IRQ FLAG
bit set to 1 and the other bits (except HOLD) set to 0.

Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
Tested-by: Kars de Jong <jongk@...ux-m68k.org>
Signed-off-by: Kars de Jong <jongk@...ux-m68k.org>
---
 drivers/rtc/rtc-msm6242.c | 20 ++++----------------
 1 file changed, 4 insertions(+), 16 deletions(-)

diff --git a/drivers/rtc/rtc-msm6242.c b/drivers/rtc/rtc-msm6242.c
index b1f2bedee77e..80e364baac53 100644
--- a/drivers/rtc/rtc-msm6242.c
+++ b/drivers/rtc/rtc-msm6242.c
@@ -88,28 +88,16 @@ static inline void msm6242_write(struct msm6242_priv *priv, unsigned int val,
 	__raw_writel(val, &priv->regs[reg]);
 }
 
-static inline void msm6242_set(struct msm6242_priv *priv, unsigned int val,
-			       unsigned int reg)
-{
-	msm6242_write(priv, msm6242_read(priv, reg) | val, reg);
-}
-
-static inline void msm6242_clear(struct msm6242_priv *priv, unsigned int val,
-				 unsigned int reg)
-{
-	msm6242_write(priv, msm6242_read(priv, reg) & ~val, reg);
-}
-
 static void msm6242_lock(struct msm6242_priv *priv)
 {
 	int cnt = 5;
 
-	msm6242_set(priv, MSM6242_CD_HOLD, MSM6242_CD);
+	msm6242_write(priv, MSM6242_CD_HOLD|MSM6242_CD_IRQ_FLAG, MSM6242_CD);
 
 	while ((msm6242_read(priv, MSM6242_CD) & MSM6242_CD_BUSY) && cnt) {
-		msm6242_clear(priv, MSM6242_CD_HOLD, MSM6242_CD);
+		msm6242_write(priv, MSM6242_CD_IRQ_FLAG, MSM6242_CD);
 		udelay(70);
-		msm6242_set(priv, MSM6242_CD_HOLD, MSM6242_CD);
+		msm6242_write(priv, MSM6242_CD_HOLD|MSM6242_CD_IRQ_FLAG, MSM6242_CD);
 		cnt--;
 	}
 
@@ -120,7 +108,7 @@ static void msm6242_lock(struct msm6242_priv *priv)
 
 static void msm6242_unlock(struct msm6242_priv *priv)
 {
-	msm6242_clear(priv, MSM6242_CD_HOLD, MSM6242_CD);
+	msm6242_write(priv, MSM6242_CD_IRQ_FLAG, MSM6242_CD);
 }
 
 static int msm6242_read_time(struct device *dev, struct rtc_time *tm)
-- 
2.17.1