pwm: Add MediaTek display PWM driver support

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@mediatek.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/Kconfig

@@ -249,6 +249,17 @@ 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
+	depends on HAS_IOMEM
+	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

drivers/pwm/Makefile

@@ -22,6 +22,7 @@ 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

drivers/pwm/pwm-mtk-disp.c

@@ -0,0 +1,243 @@
+/*
+ * MediaTek display pulse-width-modulation controller driver.
+ * Copyright (c) 2015 MediaTek Inc.
+ * Author: YH Huang <yh.huang@mediatek.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/platform_device.h>
+#include <linux/pwm.h>
+#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_BIT_WIDTH	12
+#define PWM_PERIOD_MASK		((1 << PWM_PERIOD_BIT_WIDTH) - 1)
+
+#define PWM_HIGH_WIDTH_SHIFT	16
+#define PWM_HIGH_WIDTH_MASK	(0x1fff << PWM_HIGH_WIDTH_SHIFT)
+
+struct mtk_disp_pwm {
+	struct pwm_chip chip;
+	struct clk *clk_main;
+	struct clk *clk_mm;
+	void __iomem *base;
+};
+
+static inline struct mtk_disp_pwm *to_mtk_disp_pwm(struct pwm_chip *chip)
+{
+	return container_of(chip, struct mtk_disp_pwm, chip);
+}
+
+static void mtk_disp_pwm_update_bits(struct mtk_disp_pwm *mdp, u32 offset,
+				     u32 mask, u32 data)
+{
+	void __iomem *address = mdp->base + offset;
+	u32 value;
+
+	value = readl(address);
+	value &= ~mask;
+	value |= data;
+	writel(value, address);
+}
+
+static int mtk_disp_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
+			       int duty_ns, int period_ns)
+{
+	struct mtk_disp_pwm *mdp = to_mtk_disp_pwm(chip);
+	u32 clk_div, period, high_width, value;
+	u64 div, rate;
+	int err;
+
+	/*
+	 * Find period, high_width and clk_div to suit duty_ns and period_ns.
+	 * Calculate proper div value to keep period value in the bound.
+	 *
+	 * period_ns = 10^9 * (clk_div + 1) * (period + 1) / PWM_CLK_RATE
+	 * duty_ns = 10^9 * (clk_div + 1) * high_width / PWM_CLK_RATE
+	 *
+	 * period = (PWM_CLK_RATE * period_ns) / (10^9 * (clk_div + 1)) - 1
+	 * high_width = (PWM_CLK_RATE * duty_ns) / (10^9 * (clk_div + 1))
+	 */
+	rate = clk_get_rate(mdp->clk_main);
+	clk_div = div_u64(rate * period_ns, NSEC_PER_SEC) >>
+			  PWM_PERIOD_BIT_WIDTH;
+	if (clk_div > PWM_CLKDIV_MAX)
+		return -EINVAL;
+
+	div = NSEC_PER_SEC * (clk_div + 1);
+	period = div64_u64(rate * period_ns, div);
+	if (period > 0)
+		period--;
+
+	high_width = div64_u64(rate * duty_ns, div);
+	value = period | (high_width << PWM_HIGH_WIDTH_SHIFT);
+
+	err = clk_enable(mdp->clk_main);
+	if (err < 0)
+		return err;
+
+	err = clk_enable(mdp->clk_mm);
+	if (err < 0) {
+		clk_disable(mdp->clk_main);
+		return err;
+	}
+
+	mtk_disp_pwm_update_bits(mdp, DISP_PWM_CON_0, PWM_CLKDIV_MASK,
+				 clk_div << PWM_CLKDIV_SHIFT);
+	mtk_disp_pwm_update_bits(mdp, DISP_PWM_CON_1,
+				 PWM_PERIOD_MASK | PWM_HIGH_WIDTH_MASK, value);
+	mtk_disp_pwm_update_bits(mdp, DISP_PWM_COMMIT, PWM_COMMIT_MASK, 1);
+	mtk_disp_pwm_update_bits(mdp, DISP_PWM_COMMIT, PWM_COMMIT_MASK, 0);
+
+	clk_disable(mdp->clk_mm);
+	clk_disable(mdp->clk_main);
+
+	return 0;
+}
+
+static int mtk_disp_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct mtk_disp_pwm *mdp = to_mtk_disp_pwm(chip);
+	int err;
+
+	err = clk_enable(mdp->clk_main);
+	if (err < 0)
+		return err;
+
+	err = clk_enable(mdp->clk_mm);
+	if (err < 0) {
+		clk_disable(mdp->clk_main);
+		return err;
+	}
+
+	mtk_disp_pwm_update_bits(mdp, DISP_PWM_EN, PWM_ENABLE_MASK, 1);
+
+	return 0;
+}
+
+static void mtk_disp_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct mtk_disp_pwm *mdp = to_mtk_disp_pwm(chip);
+
+	mtk_disp_pwm_update_bits(mdp, DISP_PWM_EN, PWM_ENABLE_MASK, 0);
+
+	clk_disable(mdp->clk_mm);
+	clk_disable(mdp->clk_main);
+}
+
+static const struct pwm_ops mtk_disp_pwm_ops = {
+	.config = mtk_disp_pwm_config,
+	.enable = mtk_disp_pwm_enable,
+	.disable = mtk_disp_pwm_disable,
+	.owner = THIS_MODULE,
+};
+
+static int mtk_disp_pwm_probe(struct platform_device *pdev)
+{
+	struct mtk_disp_pwm *mdp;
+	struct resource *r;
+	int ret;
+
+	mdp = devm_kzalloc(&pdev->dev, sizeof(*mdp), GFP_KERNEL);
+	if (!mdp)
+		return -ENOMEM;
+
+	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	mdp->base = devm_ioremap_resource(&pdev->dev, r);
+	if (IS_ERR(mdp->base))
+		return PTR_ERR(mdp->base);
+
+	mdp->clk_main = devm_clk_get(&pdev->dev, "main");
+	if (IS_ERR(mdp->clk_main))
+		return PTR_ERR(mdp->clk_main);
+
+	mdp->clk_mm = devm_clk_get(&pdev->dev, "mm");
+	if (IS_ERR(mdp->clk_mm))
+		return PTR_ERR(mdp->clk_mm);
+
+	ret = clk_prepare(mdp->clk_main);
+	if (ret < 0)
+		return ret;
+
+	ret = clk_prepare(mdp->clk_mm);
+	if (ret < 0)
+		goto disable_clk_main;
+
+	mdp->chip.dev = &pdev->dev;
+	mdp->chip.ops = &mtk_disp_pwm_ops;
+	mdp->chip.base = -1;
+	mdp->chip.npwm = 1;
+
+	ret = pwmchip_add(&mdp->chip);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
+		goto disable_clk_mm;
+	}
+
+	platform_set_drvdata(pdev, mdp);
+
+	return 0;
+
+disable_clk_mm:
+	clk_unprepare(mdp->clk_mm);
+disable_clk_main:
+	clk_unprepare(mdp->clk_main);
+	return ret;
+}
+
+static int mtk_disp_pwm_remove(struct platform_device *pdev)
+{
+	struct mtk_disp_pwm *mdp = platform_get_drvdata(pdev);
+	int ret;
+
+	ret = pwmchip_remove(&mdp->chip);
+	clk_unprepare(mdp->clk_mm);
+	clk_unprepare(mdp->clk_main);
+
+	return ret;
+}
+
+static const struct of_device_id mtk_disp_pwm_of_match[] = {
+	{ .compatible = "mediatek,mt8173-disp-pwm" },
+	{ .compatible = "mediatek,mt6595-disp-pwm" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, mtk_disp_pwm_of_match);
+
+static struct platform_driver mtk_disp_pwm_driver = {
+	.driver = {
+		.name = "mediatek-disp-pwm",
+		.of_match_table = mtk_disp_pwm_of_match,
+	},
+	.probe = mtk_disp_pwm_probe,
+	.remove = mtk_disp_pwm_remove,
+};
+module_platform_driver(mtk_disp_pwm_driver);
+
+MODULE_AUTHOR("YH Huang <yh.huang@mediatek.com>");
+MODULE_DESCRIPTION("MediaTek SoC display PWM driver");
+MODULE_LICENSE("GPL v2");