linux-kernel - Re: [PATCH v3 2/2] pwm: add MediaTek display PWM driver support

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Date:	Thu, 2 Jul 2015 16:14:28 +0800
From:	Daniel Kurtz <djkurtz@...omium.org>
To:	YH Huang <yh.huang@...iatek.com>
Cc:	Matthias Brugger <matthias.bgg@...il.com>,
	Mark Rutland <mark.rutland@....com>,
	Thierry Reding <thierry.reding@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>, linux-pwm@...r.kernel.org,
	"open list:OPEN FIRMWARE AND..." <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	srv_heupstream <srv_heupstream@...iatek.com>,
	linux-mediatek@...ts.infradead.org,
	Sascha Hauer <kernel@...gutronix.de>,
	Yingjoe Chen <yingjoe.chen@...iatek.com>
Subject: Re: [PATCH v3 2/2] pwm: add MediaTek display PWM driver support

On Mon, Jun 29, 2015 at 11:03 PM, YH Huang <yh.huang@...iatek.com> wrote:
> 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.
>
> Change-Id: Ie85b295e2dddd90b4163af1c906df977f79b59d6
> Signed-off-by: YH Huang <yh.huang@...iatek.com>
> ---
>  drivers/pwm/Kconfig        |  10 ++
>  drivers/pwm/Makefile       |   1 +
>  drivers/pwm/pwm-mtk-disp.c | 256 +++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 267 insertions(+)
>  create mode 100644 drivers/pwm/pwm-mtk-disp.c
>
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index b1541f4..90e3c079 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 HAS_IOMEM

depends on ARCH_MEDIATEK || COMPILE_TEST

> +       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
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index ec50eb5..99c9e75 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -18,6 +18,7 @@ obj-$(CONFIG_PWM_LPC32XX)     += pwm-lpc32xx.o
>  obj-$(CONFIG_PWM_LPSS)         += pwm-lpss.o
>  obj-$(CONFIG_PWM_LPSS_PCI)     += pwm-lpss-pci.o
>  obj-$(CONFIG_PWM_LPSS_PLATFORM)        += pwm-lpss-platform.o
> +obj-$(CONFIG_PWM_MTK_DISP)     += pwm-mtk-disp.o
>  obj-$(CONFIG_PWM_MXS)          += pwm-mxs.o
>  obj-$(CONFIG_PWM_PCA9685)      += pwm-pca9685.o
>  obj-$(CONFIG_PWM_PUV3)         += pwm-puv3.o
> diff --git a/drivers/pwm/pwm-mtk-disp.c b/drivers/pwm/pwm-mtk-disp.c
> new file mode 100644
> index 0000000..fb3a42e
> --- /dev/null
> +++ b/drivers/pwm/pwm-mtk-disp.c
> @@ -0,0 +1,256 @@
> +/*
> + * MediaTek display pulse-width-modulation controller driver.
> + * Copyright (c) 2015 MediaTek Inc.
> + * Author: YH Huang <yh.huang@...iatek.com>
> + *
> + * 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>
> +#include <linux/slab.h>
> +
> +#define DISP_PWM_EN            0x0
> +#define PWM_ENABLE_MASK                0x1

For one bit fields like this, it is nicer to use: BIT()

Thanks!
-Dan
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