On Tue, 2015-05-12 at 14:37 +0200, Matthias Brugger wrote:

Hi YH,

2015-05-11 11:26 GMT+02:00 YH Huang [off-list ref]:

quoted

Add display PWM driver support to modify backlight for MT8173/MT6595.

Signed-off-by: YH Huang <redacted>
---
 drivers/pwm/Kconfig             |   9 ++
 drivers/pwm/Makefile            |   1 +
 drivers/pwm/pwm-disp-mediatek.c | 225 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 235 insertions(+)
 create mode 100644 drivers/pwm/pwm-disp-mediatek.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index b1541f4..9edbb5a 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig

@@ -111,6 +111,15 @@ config PWM_CLPS711X
          To compile this driver as a module, choose M here: the module
          will be called pwm-clps711x.

+config PWM_DISP_MEDIATEK
+       tristate "MEDIATEK display PWM driver"
+       depends on OF
+       help
+         Generic PWM framework driver for mediatek disp-pwm device.
+
+         To compile this driver as a module, choose M here: the module
+         will be called pwm-disp-mediatek.
+
 config PWM_EP93XX
        tristate "Cirrus Logic EP93xx PWM support"
        depends on ARCH_EP93XX

diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index ec50eb5..c5ff72a 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile

@@ -8,6 +8,7 @@ obj-$(CONFIG_PWM_BCM_KONA)      += pwm-bcm-kona.o
 obj-$(CONFIG_PWM_BCM2835)      += pwm-bcm2835.o
 obj-$(CONFIG_PWM_BFIN)         += pwm-bfin.o
 obj-$(CONFIG_PWM_CLPS711X)     += pwm-clps711x.o
+obj-$(CONFIG_PWM_DISP_MEDIATEK)        += pwm-disp-mediatek.o
 obj-$(CONFIG_PWM_EP93XX)       += pwm-ep93xx.o
 obj-$(CONFIG_PWM_FSL_FTM)      += pwm-fsl-ftm.o
 obj-$(CONFIG_PWM_IMG)          += pwm-img.o

diff --git a/drivers/pwm/pwm-disp-mediatek.c b/drivers/pwm/pwm-disp-mediatek.c
new file mode 100644
index 0000000..38293af
--- /dev/null
+++ b/drivers/pwm/pwm-disp-mediatek.c

@@ -0,0 +1,225 @@
+/*
+ * 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_OFF                        (0x0)
+#define PWM_ENABLE_SHIFT               (0x0)
+#define PWM_ENABLE_MASK                        (0x1 << PWM_ENABLE_SHIFT)

Get rid of the _SHIFT which are actually zero, it will make the code
more readable.

It seems unnecessary to add it and I will fix it.

quoted

+
+#define DISP_PWM_COMMIT_OFF            (0x08)
+#define PWM_COMMIT_SHIFT               (0x0)
+#define PWM_COMMIT_MASK                        (0x1 << PWM_COMMIT_SHIFT)
+
+#define DISP_PWM_CON_0_OFF             (0x10)
+#define PWM_CLKDIV_SHIFT               (0x10)
+#define PWM_CLKDIV_MASK                        (0x3ff << PWM_CLKDIV_SHIFT)
+#define PWM_CLKDIV_MAX                 (0x000003ff)
+
+#define DISP_PWM_CON_1_OFF             (0x14)
+#define PWM_PERIOD_SHIFT               (0x0)
+#define PWM_PERIOD_MASK                        (0xfff << PWM_PERIOD_SHIFT)
+#define PWM_PERIOD_MAX                 (0x00000fff)
+/* Shift log2(PWM_PERIOD_MAX + 1) as divisor */
+#define PWM_PERIOD_BIT_SHIFT           12
+
+#define PWM_HIGH_WIDTH_SHIFT           (0x10)
+#define PWM_HIGH_WIDTH_MASK            (0x1fff << PWM_HIGH_WIDTH_SHIFT)
+
+#define NUM_PWM 1
+
+struct mtk_disp_pwm_chip {
+       struct pwm_chip chip;
+       struct device   *dev;
+       struct clk      *clk_main;
+       struct clk      *clk_mm;
+       void __iomem    *mmio_base;
+};
+
+static void mtk_disp_pwm_setting(void __iomem *address, u32 value, u32 mask)
+{
+       u32 val;
+
+       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_chip *mpc;
+       u64 div, rate;
+       u32 clk_div, period, high_width, rem;
+
+       /*
+        * 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 + 1) / 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)) - 1
+        */
+       mpc = container_of(chip, struct mtk_disp_pwm_chip, chip);
+       rate = clk_get_rate(mpc->clk_main);
+       clk_div = div_u64_rem(rate * period_ns, NSEC_PER_SEC, &rem) >>
+                               PWM_PERIOD_BIT_SHIFT;

You never use the remainder, so better use div_u64 to make the code cleaner.

OK.

quoted

+       if (clk_div > PWM_CLKDIV_MAX)
+               return -EINVAL;
+
+       div = clk_div + 1;
+       period = div64_u64(rate * period_ns, NSEC_PER_SEC * div);
+       if (period > 0)
+               period--;
+       high_width = div64_u64(rate * duty_ns, NSEC_PER_SEC * div);
+       if (high_width > 0)
+               high_width--;
+
+       mtk_disp_pwm_setting(mpc->mmio_base + DISP_PWM_CON_0_OFF,
+                            clk_div << PWM_CLKDIV_SHIFT, PWM_CLKDIV_MASK);
+       mtk_disp_pwm_setting(mpc->mmio_base + DISP_PWM_CON_1_OFF,
+                            (period << PWM_PERIOD_SHIFT) |
+                       (high_width << PWM_HIGH_WIDTH_SHIFT),
+                       PWM_PERIOD_MASK | PWM_HIGH_WIDTH_MASK);
+
+       mtk_disp_pwm_setting(mpc->mmio_base + DISP_PWM_COMMIT_OFF,
+                            1 << PWM_COMMIT_SHIFT, PWM_COMMIT_MASK);
+       mtk_disp_pwm_setting(mpc->mmio_base + DISP_PWM_COMMIT_OFF,
+                            0 << PWM_COMMIT_SHIFT, PWM_COMMIT_MASK);
+
+       return 0;
+}
+
+static int mtk_disp_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+       struct mtk_disp_pwm_chip *mpc;
+
+       mpc = container_of(chip, struct mtk_disp_pwm_chip, chip);
+       mtk_disp_pwm_setting(mpc->mmio_base + DISP_PWM_EN_OFF,
+                            1 << PWM_ENABLE_SHIFT, PWM_ENABLE_MASK);
+
+       return 0;
+}
+
+static void mtk_disp_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+       struct mtk_disp_pwm_chip *mpc;
+
+       mpc = container_of(chip, struct mtk_disp_pwm_chip, chip);
+       mtk_disp_pwm_setting(mpc->mmio_base + DISP_PWM_EN_OFF,
+                            0 << PWM_ENABLE_SHIFT, PWM_ENABLE_MASK);
+}
+
+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_chip *pwm;
+       struct resource *r;
+       int ret;
+
+       pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
+       if (!pwm)
+               return -ENOMEM;
+
+       pwm->dev = &pdev->dev;
+
+       r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+       pwm->mmio_base = devm_ioremap_resource(&pdev->dev, r);
+       if (IS_ERR(pwm->mmio_base))
+               return PTR_ERR(pwm->mmio_base);
+
+       pwm->clk_main = devm_clk_get(&pdev->dev, "main");
+       if (IS_ERR(pwm->clk_main))
+               return PTR_ERR(pwm->clk_main);

I prefer to have a newline after the if-then-ese block, which makes it
(at least for me) easier to read the code.

OK.

Thanks,
Matthias

Thank for your suggestion.

Regards,
YH Huang