linux-kernel - [PATCH 3.16 004/133] backlight: lm3630a: Bump REG

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Date:   Wed, 22 Nov 2017 01:58:12 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Lee Jones" <lee.jones@...aro.org>,
        "Bjorn Andersson" <bjorn.andersson@...aro.org>,
        "Bhushan Shah" <bshah@....org>,
        "Daniel Thompson" <daniel.thompson@...aro.org>
Subject: [PATCH 3.16 004/133] backlight: lm3630a: Bump REG_MAX value to
 0x50 instead of 0x1F

3.16.51-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Bhushan Shah <bshah@....org>

commit 06168a64b1ae346816fcd0a0c3ea5276c778408b upstream.

In the lm3630a_chip_init we try to write to 0x50 register, which is
higher value then the max_register value, this resulted in regmap_write
return -EIO.

Fix this by bumping REG_MAX value to 0x50.

This code was introduced with the chip revision in commit 28e64a68a2ef,
however setting filter strength was failing silently because it used
unsigned int for storing and comparing the return values. Bug related to
signedness was fixed in 2a0c316bf3cc, which made it error out correctly
instead of failing silently.

I found this issue by using this driver on LGE Nexus 5 (hammerhead).
After this commit lm3630a_chip_init succeeds instead of failing with
-EIO.

Fixes: 28e64a68a2ef ("backlight: lm3630: apply chip revision")
Fixes: 2a0c316bf3cc ("drivers/video/backlight/lm3630a_bl.c: fix
signedness bug in lm3630a_chip_init()")

Suggested-by: Bjorn Andersson <bjorn.andersson@...aro.org>
Signed-off-by: Bhushan Shah <bshah@....org>
Acked-by: Daniel Thompson <daniel.thompson@...aro.org>
Signed-off-by: Lee Jones <lee.jones@...aro.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/video/backlight/lm3630a_bl.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/video/backlight/lm3630a_bl.c
+++ b/drivers/video/backlight/lm3630a_bl.c
@@ -31,7 +31,8 @@
 #define REG_FAULT	0x0B
 #define REG_PWM_OUTLOW	0x12
 #define REG_PWM_OUTHIGH	0x13
-#define REG_MAX		0x1F
+#define REG_FILTER_STRENGTH	0x50
+#define REG_MAX		0x50
 
 #define INT_DEBOUNCE_MSEC	10
 struct lm3630a_chip {
@@ -80,7 +81,7 @@ static int lm3630a_chip_init(struct lm36
 
 	usleep_range(1000, 2000);
 	/* set Filter Strength Register */
-	rval = lm3630a_write(pchip, 0x50, 0x03);
+	rval = lm3630a_write(pchip, REG_FILTER_STRENGTH, 0x03);
 	/* set Cofig. register */
 	rval |= lm3630a_update(pchip, REG_CONFIG, 0x07, pdata->pwm_ctrl);
 	/* set boost control */