Hi YH,

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

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

+
+#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.

+       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.

Thanks,
Matthias
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