[PATCH v6 2/3] pwm: add MediaTek display PWM driver support

YH Huang
2015-07-20T08:18:09Z

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>
---
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
+ 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..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@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/pwm.h>
+#include <linux/platform_device.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_MASK 0xfff
+/* Shift log2(PWM_PERIOD_MASK + 1) as divisor */
+#define PWM_PERIOD_BIT_SHIFT 12
+
+#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 value)
+{
+ void __iomem *address;
+ u32 val;
+
+ address = mdp->base + offset;
+ val = readl(address);
+ val &= ~mask;
+ val |= value;
+ writel(val, 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);
+ u64 div, rate;
+ u32 clk_div, period, high_width, value;
+
+ /*
+ * 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_SHIFT;
+ 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);
+
+ clk_enable(mdp->clk_main);
+ clk_enable(mdp->clk_mm);
+
+ 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);
+
+ clk_enable(mdp->clk_main);
+ clk_enable(mdp->clk_mm);
+
+ 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 = 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");
--
1.8.1.1.dirty