On Tue, 2015-05-12 at 15:32 +0200, Thierry Reding wrote:

On Mon, May 11, 2015 at 05:26:22PM +0800, YH Huang wrote:

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

Please make this "PWM_MEDIATEK_DISP" so we can keep everything sorted by
vendor.

Probably "PWM_MTK_DSIP" for Matthias opinion?

quoted

+	tristate "MEDIATEK display PWM driver"

"MediaTek"?

OK.

quoted

+	depends on OF

Technically I think you need depends on HAS_IOMEM here to avoid breakage
on randconfig builds.

OK.

quoted

+	help
+	  Generic PWM framework driver for mediatek disp-pwm device.

"MediaTek"? Also perhaps this should describe what this PWM is instead
of just the "disp-pwm" which leaves everyone guessing what it is. From
the name I'd expect it to be the PWM that is used to control the
backlight brightness for display, but I think this description should
say that explicitly.

quoted

+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-disp-mediatek.

pwm-mediatek-disp

pwm-mtk-disp?

quoted

+
 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

Also name this "pwm-mediatek-disp.o" to reflect the Kconfig name.

pwm-mtk-disp.o?

quoted

 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)

The _OFF suffix here is unfortunate because I'm reading this as being
the "OFF" value for a field named "DISP_PWM_EN". I think it'd be better
to name this one DISP_PWM_EN. The same goes for any of the following
registers.

Also, drop the parentheses if the expression is simple.

OK. It is really confusing.

quoted

+#define PWM_ENABLE_SHIFT		(0x0)
+#define PWM_ENABLE_MASK			(0x1 << PWM_ENABLE_SHIFT)
+
+#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

This is confusing, see below.

I don't really understand what does this mean.
Please help me.

quoted

+
+#define PWM_HIGH_WIDTH_SHIFT		(0x10)
+#define PWM_HIGH_WIDTH_MASK		(0x1fff << PWM_HIGH_WIDTH_SHIFT)
+
+#define NUM_PWM 1

You can drop this, it's only used once.

OK.

quoted

+
+struct mtk_disp_pwm_chip {
+	struct pwm_chip	chip;
+	struct device	*dev;
+	struct clk	*clk_main;
+	struct clk	*clk_mm;
+	void __iomem	*mmio_base;
+};

Please don't add this artificial padding, a single space is enough as a
separator. Also, I think you can drop the _chip suffix on the structure
name.

OK.

quoted

+
+static void mtk_disp_pwm_setting(void __iomem *address, u32 value, u32 mask)

This is a bad name. I think you should adopt the naming of regmap, which
this effectively copies, so this should be:

	static void mtk_disp_pwm_update_bits(void __iomem *address, u32 mask, u32 value)

It is much readable.

quoted

+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);

Can you add a static inline function to wrap the container_of()
invocation? You need to do this quite often and the wrapper will shorten
the code significantly:

	static inline struct mtk_disp_pwm *to_mtk_disp_pwm(struct pwm_chip *chip)
	{
		return container_of(chip, struct mtk_disp_pwm, chip);
	}

Also it's slightly more canonical to initialize the mpc variable as part
of the declaration.

This is a good way to shorten the code.

quoted

+	rate = clk_get_rate(mpc->clk_main);
+	clk_div = div_u64_rem(rate * period_ns, NSEC_PER_SEC, &rem) >>
+				PWM_PERIOD_BIT_SHIFT;
+	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);

Can you align these differently to make it more readable?

	mtk_display_pwm_update_bits(mpc->mmio_base + DISP_PWM_CON_1,
				    PWM_PERIOD_MASK | PWM_HIGH_WIDTH_MASK,
				    (period << PWM_PERIOD_SHIFT) |
					(high_width << PWM_HIGH_WIDTH_SHIFT));

Or perhaps split it into multiple steps to make it even more readable:

	value = (high_width << PWM_HIGH_WIDTH_SHIFT) |
		(period << PWM_PERIOD_SHIFT);
	mtk_display_pwm_update_bits(mpc->mmio_base + DISP_PWM_CON_1,
				    PWM_HIGH_WIDTH_MASK | PWM_PERIOD_MASK,
				    value);

OK, it is really hard to read.

quoted

+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);
+	pwm->clk_mm = devm_clk_get(&pdev->dev, "mm");

I think it's more readable if a blank line separates the above two
lines.

OK.

quoted

+	if (IS_ERR(pwm->clk_mm))
+		return PTR_ERR(pwm->clk_mm);
+
+	ret = clk_prepare_enable(pwm->clk_main);
+	if (ret < 0)
+		return ret;
+	ret = clk_prepare_enable(pwm->clk_mm);

Same here.

OK.

quoted

+	if (ret < 0) {
+		clk_disable_unprepare(pwm->clk_main);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, pwm);
+
+	pwm->chip.dev = &pdev->dev;
+	pwm->chip.ops = &mtk_disp_pwm_ops;
+	pwm->chip.base = -1;
+	pwm->chip.npwm = NUM_PWM;
+
+	ret = pwmchip_add(&pwm->chip);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);

Shouldn't you disable the clocks here?

I will fix it.

quoted

+		return ret;
+	}
+
+	return 0;
+}
+
+static int mtk_disp_pwm_remove(struct platform_device *pdev)
+{
+	struct mtk_disp_pwm_chip *pc = platform_get_drvdata(pdev);
+
+	if (WARN_ON(!pc))
+		return -ENODEV;

You can drop this. Better to let it crash so that you have to fix it if
you ever encounter it.

I will think about it.

quoted

+
+	clk_disable_unprepare(pc->clk_main);
+	clk_disable_unprepare(pc->clk_mm);
+
+	return pwmchip_remove(&pc->chip);
+}
+
+static const struct of_device_id mtk_disp_pwm_of_match[] = {
+	{ .compatible = "mediatek,mt6595-disp-pwm" },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(of, mtk_disp_pwm_of_match);

No blank line between the above two lines.

OK.

quoted

+
+static struct platform_driver mtk_disp_pwm_driver = {
+	.driver = {
+		.name = "mediatek-disp-pwm",
+		.owner = THIS_MODULE,
+		.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);

Same here. Also, no need to initialize .driver.owner,
module_platform_driver() does that for you.

Got it.

Thierry

Thank for your suggestion.

Regards,
YH Huang