On Mon, 2015-08-17 at 15:23 +0200, Thierry Reding wrote:

On Mon, Jul 20, 2015 at 04:17:16PM +0800, YH Huang wrote:

quoted

Add display PWM driver support to modify backlight for MT8173 and MT6595.
The PWM has one channel to control the brightness of the display.
When the (high_width / period) is closer to 1, the screen is brighter;
otherwise, it is darker.

Signed-off-by: YH Huang <yh.huang-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>
---
 drivers/pwm/Kconfig        |  10 ++
 drivers/pwm/Makefile       |   1 +
 drivers/pwm/pwm-mtk-disp.c | 232 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 243 insertions(+)
 create mode 100644 drivers/pwm/pwm-mtk-disp.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index b1541f4..f5b03a4 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig

@@ -211,6 +211,16 @@ config PWM_LPSS_PLATFORM
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-lpss-platform.
 
+config PWM_MTK_DISP
+	tristate "MediaTek display PWM driver"
+	depends on ARCH_MEDIATEK || COMPILE_TEST

This is going to break randconfig builds. From a quick look your driver
will fail to build at least on architectures that don't set HAVE_IOMEM.
I know that's quite exotic, but I've had to deal with fallout from
things like this in the past. If you want || COMPILE_TEST you should at
least add a "depends on HAVE_IOMEM".

linux/clk.h seems to have stubs for all of the functions that you use,
so those shouldn't be a problem.

I will add it and this will be like:

depends on ARCH_MEDIATEK || COMPILE_TEST
depends on HAS_IOMEM

quoted

+	help
+	  Generic PWM framework driver for MediaTek disp-pwm device.
+	  The PWM is used to control the backlight brightness for display.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-mtk-disp.
+
 config PWM_MXS
 	tristate "Freescale MXS PWM support"
 	depends on ARCH_MXS && OF

[...]

quoted

diff --git a/drivers/pwm/pwm-mtk-disp.c b/drivers/pwm/pwm-mtk-disp.c
new file mode 100644
index 0000000..69682a0
--- /dev/null
+++ b/drivers/pwm/pwm-mtk-disp.c

@@ -0,0 +1,232 @@
+/*
+ * MediaTek display pulse-width-modulation controller driver.
+ * Copyright (c) 2015 MediaTek Inc.
+ * Author: YH Huang <yh.huang-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/pwm.h>
+#include <linux/platform_device.h>

The above two aren't correctly sorted.

Arrange like this:

#include <linux/platform_device.h>
#include <linux/pwm.h>

quoted

+#include <linux/slab.h>
+
+#define DISP_PWM_EN		0x00
+#define PWM_ENABLE_MASK		BIT(0)
+
+#define DISP_PWM_COMMIT		0x08
+#define PWM_COMMIT_MASK		BIT(0)
+
+#define DISP_PWM_CON_0		0x10
+#define PWM_CLKDIV_SHIFT	16
+#define PWM_CLKDIV_MAX		0x3ff
+#define PWM_CLKDIV_MASK		(PWM_CLKDIV_MAX << PWM_CLKDIV_SHIFT)
+
+#define DISP_PWM_CON_1		0x14
+#define PWM_PERIOD_MASK		0xfff
+/* Shift log2(PWM_PERIOD_MASK + 1) as divisor */
+#define PWM_PERIOD_BIT_SHIFT	12

There are still two names for the same value here. I thought we had
agreed on this becoming something like the below?

	#define PWM_PERIOD_BIT_SHIFT 12
	#define PWM_PERIOD_MASK ((1 << PWM_PERIOD_BIT_SHIFT) - 1)

Although PWM_PERIOD_BIT_WIDTH would probably be a better name. Or
PWM_PERIOD_BITS or similar.

I will revise to 

#define PWM_PERIOD_BIT_WIDTH 12
#define PWM_PERIOD_MASK ((1 << PWM_PERIOD_BIT_WIDTH) - 1)

quoted

+static int mtk_disp_pwm_remove(struct platform_device *pdev)
+{
+	struct mtk_disp_pwm *mdp = platform_get_drvdata(pdev);
+	int ret = pwmchip_remove(&mdp->chip);

I'd prefer this to be separate lines:

	int ret;

	ret = pwmchip_remove(&mdp->chip);

OK.

Thanks for your suggestions.

Regards,
YH Huang


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