[PATCH v5 0/2] pwm: Introduce pwm driver for the Loongson family chips

[PATCH v5 0/2] pwm: Introduce pwm driver for the Loongson family chips

[Binbin Zhou]

Hi all:

This patchset introduce a generic PWM framework driver for Loongson family.
Each PWM has one pulse width output signal and one pulse input signal to be measured.

It can be found on Loongson-2K series cpus and Loongson LS7A bridge chips.

Thanks.

-------
V5:
patch (2/2):
 - Rebase on pwm/for-next;
 - Test with PWM_DEBUG enabled;
 - Rewrote pwm_loongson_apply() and adjusted the order of pwm status and
   polarity to avoid test failure;
 - Added DIV64_U64_ROUND_UP in pwm_loongson_get_state() to avoid
   precision loss and to avoid test failures.

Link to V4:
https://lore.kernel.org/all/cover.1716795485.git.zhoubinbin@loongson.cn/

V4:
patch (2/2):
 - Rebase on pwm/for-next;
 - Addressed Uwe's review comments:
   - Make use of devm_pwmchip_alloc() function;
   - Add Limitations description;
   - Add LOONGSON_ prefix for Loongson pwm register defines;
   - Keep regs written only once;
   - Rewrite duty/period calculation;
   - Add dev_err_probe() in .probe();
   - Fix some code style.

Link to V3:
https://lore.kernel.org/linux-pwm/cover.1713164810.git.zhoubinbin@loongson.cn/

V3:
patch (1/2):
 - Add Reviewed-by tag from Krzysztof, thanks.
patch (2/2):
 - Several code stlye adjustments, such as line breaks.

Link to V2:
https://lore.kernel.org/all/cover.1712732719.git.zhoubinbin@loongson.cn/

v2:
- Remove the dts-related patches and update dts at once after all
relevant drivers are complete.
patch (1/2):
 - The dt-binding filename should match compatible, rename it as
   loongson,ls7a-pwm.yaml;
 - Update binding description;
 - Add description for each pwm cell;
 - Drop '#pwm-cells' from required, for pwm.yaml makes it required already.

Link to v1:
https://lore.kernel.org/linux-pwm/cover.1711953223.git.zhoubinbin@loongson.cn/

Binbin Zhou (2):
  dt-bindings: pwm: Add Loongson PWM controller
  pwm: Add Loongson PWM controller support

 .../bindings/pwm/loongson,ls7a-pwm.yaml       |  66 ++++
 MAINTAINERS                                   |   7 +
 drivers/pwm/Kconfig                           |  12 +
 drivers/pwm/Makefile                          |   1 +
 drivers/pwm/pwm-loongson.c                    | 285 ++++++++++++++++++
 5 files changed, 371 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/pwm/loongson,ls7a-pwm.yaml
 create mode 100644 drivers/pwm/pwm-loongson.c

-- 
2.43.5

[PATCH v5 1/2] dt-bindings: pwm: Add Loongson PWM controller

[Binbin Zhou]

Add Loongson PWM controller binding with DT schema format using
json-schema.

Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Huacai Chen <chenhuacai@loongson.cn>
---
 .../bindings/pwm/loongson,ls7a-pwm.yaml       | 66 +++++++++++++++++++
 MAINTAINERS                                   |  6 ++
 2 files changed, 72 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/pwm/loongson,ls7a-pwm.yaml

diff --git a/Documentation/devicetree/bindings/pwm/loongson,ls7a-pwm.yaml b/Documentation/devicetree/bindings/pwm/loongson,ls7a-pwm.yaml
new file mode 100644
index 000000000000..46814773e0cc
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/loongson,ls7a-pwm.yaml
@@ -0,0 +1,66 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pwm/loongson,ls7a-pwm.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Loongson PWM Controller
+
+maintainers:
+  - Binbin Zhou <zhoubinbin@loongson.cn>
+
+description:
+  The Loongson PWM has one pulse width output signal and one pulse input
+  signal to be measured.
+  It can be found on Loongson-2K series cpus and Loongson LS7A bridge chips.
+
+allOf:
+  - $ref: pwm.yaml#
+
+properties:
+  compatible:
+    oneOf:
+      - const: loongson,ls7a-pwm
+      - items:
+          - enum:
+              - loongson,ls2k0500-pwm
+              - loongson,ls2k1000-pwm
+              - loongson,ls2k2000-pwm
+          - const: loongson,ls7a-pwm
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  '#pwm-cells':
+    description:
+      The first cell must have a value of 0, which specifies the PWM output signal;
+      The second cell is the period in nanoseconds;
+      The third cell flag supported by this binding is PWM_POLARITY_INVERTED.
+    const: 3
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    #include <dt-bindings/clock/loongson,ls2k-clk.h>
+    pwm@1fe22000 {
+        compatible = "loongson,ls2k1000-pwm", "loongson,ls7a-pwm";
+        reg = <0x1fe22000 0x10>;
+        interrupt-parent = <&liointc0>;
+        interrupts = <24 IRQ_TYPE_LEVEL_HIGH>;
+        clocks = <&clk LOONGSON2_APB_CLK>;
+        #pwm-cells = <3>;
+    };
diff --git a/MAINTAINERS b/MAINTAINERS
index efa9e7b653a6..973d60113105 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12989,6 +12989,12 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/i2c/loongson,ls2x-i2c.yaml
 F:	drivers/i2c/busses/i2c-ls2x.c
 
+LOONGSON PWM DRIVER
+M:	Binbin Zhou <zhoubinbin@loongson.cn>
+L:	linux-pwm@vger.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/pwm/loongson,ls7a-pwm.yaml
+
 LOONGSON-2 SOC SERIES CLOCK DRIVER
 M:	Yinbo Zhu <zhuyinbo@loongson.cn>
 L:	linux-clk@vger.kernel.org
-- 
2.43.5

[PATCH v5 2/2] pwm: Add Loongson PWM controller support

[Binbin Zhou]

This commit adds a generic PWM framework driver for the PWM controller
found on Loongson family chips.

Co-developed-by: Juxin Gao <gaojuxin@loongson.cn>
Signed-off-by: Juxin Gao <gaojuxin@loongson.cn>
Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Acked-by: Huacai Chen <chenhuacai@loongson.cn>
---
 MAINTAINERS                |   1 +
 drivers/pwm/Kconfig        |  12 ++
 drivers/pwm/Makefile       |   1 +
 drivers/pwm/pwm-loongson.c | 285 +++++++++++++++++++++++++++++++++++++
 4 files changed, 299 insertions(+)
 create mode 100644 drivers/pwm/pwm-loongson.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 973d60113105..2222d036057a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12994,6 +12994,7 @@ M:	Binbin Zhou <zhoubinbin@loongson.cn>
 L:	linux-pwm@vger.kernel.org
 S:	Maintained
 F:	Documentation/devicetree/bindings/pwm/loongson,ls7a-pwm.yaml
+F:	drivers/pwm/pwm-loongson.c
 
 LOONGSON-2 SOC SERIES CLOCK DRIVER
 M:	Yinbo Zhu <zhuyinbo@loongson.cn>
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 1dd7921194f5..839a63ccda0e 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -320,6 +320,18 @@ config PWM_KEEMBAY
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-keembay.
 
+config PWM_LOONGSON
+	tristate "Loongson PWM support"
+	depends on MACH_LOONGSON64 || COMPILE_TEST
+	depends on COMMON_CLK
+	help
+	  Generic PWM framework driver for Loongson family.
+	  It can be found on Loongson-2K series cpus and Loongson LS7A
+	  bridge chips.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-loongson.
+
 config PWM_LP3943
 	tristate "TI/National Semiconductor LP3943 PWM support"
 	depends on MFD_LP3943
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 90913519f11a..032d73327509 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -27,6 +27,7 @@ obj-$(CONFIG_PWM_INTEL_LGM)	+= pwm-intel-lgm.o
 obj-$(CONFIG_PWM_IQS620A)	+= pwm-iqs620a.o
 obj-$(CONFIG_PWM_JZ4740)	+= pwm-jz4740.o
 obj-$(CONFIG_PWM_KEEMBAY)	+= pwm-keembay.o
+obj-$(CONFIG_PWM_LOONGSON)	+= pwm-loongson.o
 obj-$(CONFIG_PWM_LP3943)	+= pwm-lp3943.o
 obj-$(CONFIG_PWM_LPC18XX_SCT)	+= pwm-lpc18xx-sct.o
 obj-$(CONFIG_PWM_LPC32XX)	+= pwm-lpc32xx.o
diff --git a/drivers/pwm/pwm-loongson.c b/drivers/pwm/pwm-loongson.c
new file mode 100644
index 000000000000..17ab2a2f48ad
--- /dev/null
+++ b/drivers/pwm/pwm-loongson.c
@@ -0,0 +1,285 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Loongson PWM driver
+ *
+ * Author: Juxin Gao <gaojuxin@loongson.cn>
+ * Further cleanup and restructuring by:
+ *         Binbin Zhou <zhoubinbin@loongson.cn>
+ *
+ * Copyright (C) 2017-2024 Loongson Technology Corporation Limited.
+ *
+ * Limitations:
+ * - The buffer register value should be written before the CTRL register.
+ * - When disabled the output is driven to 0 independent of the configured
+ *   polarity.
+ */
+
+#include <linux/acpi.h>
+#include <linux/clk.h>
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/units.h>
+
+/* Loongson PWM registers */
+#define LOONGSON_PWM_REG_DUTY		0x4 /* Low Pulse Buffer Register */
+#define LOONGSON_PWM_REG_PERIOD		0x8 /* Pulse Period Buffer Register */
+#define LOONGSON_PWM_REG_CTRL		0xc /* Control Register */
+
+/* Control register bits */
+#define LOONGSON_PWM_CTRL_EN		BIT(0)  /* Counter Enable Bit */
+#define LOONGSON_PWM_CTRL_OE		BIT(3)  /* Pulse Output Enable Control Bit, Valid Low */
+#define LOONGSON_PWM_CTRL_SINGLE	BIT(4)  /* Single Pulse Control Bit */
+#define LOONGSON_PWM_CTRL_INTE		BIT(5)  /* Interrupt Enable Bit */
+#define LOONGSON_PWM_CTRL_INT		BIT(6)  /* Interrupt Bit */
+#define LOONGSON_PWM_CTRL_RST		BIT(7)  /* Counter Reset Bit */
+#define LOONGSON_PWM_CTRL_CAPTE		BIT(8)  /* Measurement Pulse Enable Bit */
+#define LOONGSON_PWM_CTRL_INVERT	BIT(9)  /* Output flip-flop Enable Bit */
+#define LOONGSON_PWM_CTRL_DZONE		BIT(10) /* Anti-dead Zone Enable Bit */
+
+#define LOONGSON_PWM_FREQ_STD		(50 * HZ_PER_KHZ)
+
+struct pwm_loongson_suspend_store {
+	u32 ctrl;
+	u32 duty;
+	u32 period;
+};
+
+struct pwm_loongson_ddata {
+	struct clk *clk;
+	void __iomem *base;
+	u64 clk_rate;
+	struct pwm_loongson_suspend_store lss;
+};
+
+static inline struct pwm_loongson_ddata *to_pwm_loongson_ddata(struct pwm_chip *chip)
+{
+	return pwmchip_get_drvdata(chip);
+}
+
+static inline u32 pwm_loongson_readl(struct pwm_loongson_ddata *ddata, u32 offset)
+{
+	return readl(ddata->base + offset);
+}
+
+static inline void pwm_loongson_writel(struct pwm_loongson_ddata *ddata,
+				       u32 val, u32 offset)
+{
+	writel(val, ddata->base + offset);
+}
+
+static int pwm_loongson_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
+				     enum pwm_polarity polarity)
+{
+	u16 val;
+	struct pwm_loongson_ddata *ddata = to_pwm_loongson_ddata(chip);
+
+	val = pwm_loongson_readl(ddata, LOONGSON_PWM_REG_CTRL);
+
+	if (polarity == PWM_POLARITY_INVERSED)
+		/* Duty cycle defines LOW period of PWM */
+		val |= LOONGSON_PWM_CTRL_INVERT;
+	else
+		/* Duty cycle defines HIGH period of PWM */
+		val &= ~LOONGSON_PWM_CTRL_INVERT;
+
+	pwm_loongson_writel(ddata, val, LOONGSON_PWM_REG_CTRL);
+
+	return 0;
+}
+
+static void pwm_loongson_disable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	u32 val;
+	struct pwm_loongson_ddata *ddata = to_pwm_loongson_ddata(chip);
+
+	val = pwm_loongson_readl(ddata, LOONGSON_PWM_REG_CTRL);
+	val &= ~LOONGSON_PWM_CTRL_EN;
+	pwm_loongson_writel(ddata, val, LOONGSON_PWM_REG_CTRL);
+}
+
+static int pwm_loongson_enable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	u32 val;
+	struct pwm_loongson_ddata *ddata = to_pwm_loongson_ddata(chip);
+
+	val = pwm_loongson_readl(ddata, LOONGSON_PWM_REG_CTRL);
+	val |= LOONGSON_PWM_CTRL_EN;
+	pwm_loongson_writel(ddata, val, LOONGSON_PWM_REG_CTRL);
+
+	return 0;
+}
+
+static int pwm_loongson_config(struct pwm_chip *chip, struct pwm_device *pwm,
+			       u64 duty_ns, u64 period_ns)
+{
+	u32 duty, period;
+	struct pwm_loongson_ddata *ddata = to_pwm_loongson_ddata(chip);
+
+	/* duty = duty_ns * ddata->clk_rate / NSEC_PER_SEC */
+	duty = mul_u64_u64_div_u64(duty_ns, ddata->clk_rate, NSEC_PER_SEC);
+	pwm_loongson_writel(ddata, duty, LOONGSON_PWM_REG_DUTY);
+
+	/* period = period_ns * ddata->clk_rate / NSEC_PER_SEC */
+	period = mul_u64_u64_div_u64(period_ns, ddata->clk_rate, NSEC_PER_SEC);
+	pwm_loongson_writel(ddata, period, LOONGSON_PWM_REG_PERIOD);
+
+	return 0;
+}
+
+static int pwm_loongson_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			      const struct pwm_state *state)
+{
+	int ret;
+	u64 period, duty_cycle;
+	bool enabled = pwm->state.enabled;
+
+	if (enabled && !state->enabled) {
+		pwm_loongson_disable(chip, pwm);
+		return 0;
+	}
+
+	if (state->polarity != pwm->state.polarity) {
+		ret = pwm_loongson_set_polarity(chip, pwm, state->polarity);
+		if (ret)
+			return ret;
+	}
+
+	period = min(state->period, NANOHZ_PER_HZ);
+	duty_cycle = min(state->duty_cycle, NANOHZ_PER_HZ);
+
+	ret = pwm_loongson_config(chip, pwm, duty_cycle, period);
+	if (ret)
+		return ret;
+
+	if (!enabled && state->enabled)
+		ret = pwm_loongson_enable(chip, pwm);
+
+	return ret;
+}
+
+static int pwm_loongson_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+				  struct pwm_state *state)
+{
+	u32 duty, period, ctrl;
+	struct pwm_loongson_ddata *ddata = to_pwm_loongson_ddata(chip);
+
+	duty = pwm_loongson_readl(ddata, LOONGSON_PWM_REG_DUTY);
+	period = pwm_loongson_readl(ddata, LOONGSON_PWM_REG_PERIOD);
+	ctrl = pwm_loongson_readl(ddata, LOONGSON_PWM_REG_CTRL);
+
+	/* duty & period have a max of 2^32, so we can't overflow */
+	state->duty_cycle = DIV64_U64_ROUND_UP((u64)duty * NSEC_PER_SEC, ddata->clk_rate);
+	state->period = DIV64_U64_ROUND_UP((u64)period * NSEC_PER_SEC, ddata->clk_rate);
+	state->polarity = (ctrl & LOONGSON_PWM_CTRL_INVERT) ? PWM_POLARITY_INVERSED :
+			  PWM_POLARITY_NORMAL;
+	state->enabled = (ctrl & LOONGSON_PWM_CTRL_EN) ? true : false;
+
+	return 0;
+}
+
+static const struct pwm_ops pwm_loongson_ops = {
+	.apply = pwm_loongson_apply,
+	.get_state = pwm_loongson_get_state,
+};
+
+static int pwm_loongson_probe(struct platform_device *pdev)
+{
+	int ret;
+	struct pwm_chip *chip;
+	struct pwm_loongson_ddata *ddata;
+	struct device *dev = &pdev->dev;
+
+	chip = devm_pwmchip_alloc(dev, 1, sizeof(*ddata));
+	if (IS_ERR(chip))
+		return PTR_ERR(chip);
+	ddata = to_pwm_loongson_ddata(chip);
+
+	ddata->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(ddata->base))
+		return PTR_ERR(ddata->base);
+
+	if (!has_acpi_companion(dev)) {
+		ddata->clk = devm_clk_get_enabled(dev, NULL);
+		if (IS_ERR(ddata->clk))
+			return dev_err_probe(dev, PTR_ERR(ddata->clk),
+					     "failed to get pwm clock\n");
+		ddata->clk_rate = clk_get_rate(ddata->clk);
+	} else {
+		ddata->clk_rate = LOONGSON_PWM_FREQ_STD;
+	}
+
+	chip->ops = &pwm_loongson_ops;
+	dev_set_drvdata(dev, chip);
+
+	ret = devm_pwmchip_add(dev, chip);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "failed to add PWM chip\n");
+
+	return 0;
+}
+
+static int pwm_loongson_suspend(struct device *dev)
+{
+	struct pwm_chip *chip = dev_get_drvdata(dev);
+	struct pwm_loongson_ddata *ddata = to_pwm_loongson_ddata(chip);
+
+	ddata->lss.ctrl = pwm_loongson_readl(ddata, LOONGSON_PWM_REG_CTRL);
+	ddata->lss.duty = pwm_loongson_readl(ddata, LOONGSON_PWM_REG_DUTY);
+	ddata->lss.period = pwm_loongson_readl(ddata, LOONGSON_PWM_REG_PERIOD);
+
+	clk_disable_unprepare(ddata->clk);
+
+	return 0;
+}
+
+static int pwm_loongson_resume(struct device *dev)
+{
+	int ret;
+	struct pwm_chip *chip = dev_get_drvdata(dev);
+	struct pwm_loongson_ddata *ddata = to_pwm_loongson_ddata(chip);
+
+	ret = clk_prepare_enable(ddata->clk);
+	if (ret)
+		return ret;
+
+	pwm_loongson_writel(ddata, ddata->lss.ctrl, LOONGSON_PWM_REG_CTRL);
+	pwm_loongson_writel(ddata, ddata->lss.duty, LOONGSON_PWM_REG_DUTY);
+	pwm_loongson_writel(ddata, ddata->lss.period, LOONGSON_PWM_REG_PERIOD);
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(pwm_loongson_pm_ops, pwm_loongson_suspend,
+				pwm_loongson_resume);
+
+static const struct of_device_id pwm_loongson_of_ids[] = {
+	{ .compatible = "loongson,ls7a-pwm" },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, pwm_loongson_of_ids);
+
+static const struct acpi_device_id pwm_loongson_acpi_ids[] = {
+	{ "LOON0006" },
+	{ }
+};
+MODULE_DEVICE_TABLE(acpi, pwm_loongson_acpi_ids);
+
+static struct platform_driver pwm_loongson_driver = {
+	.probe = pwm_loongson_probe,
+	.driver = {
+		.name = "loongson-pwm",
+		.pm = pm_ptr(&pwm_loongson_pm_ops),
+		.of_match_table = pwm_loongson_of_ids,
+		.acpi_match_table = pwm_loongson_acpi_ids,
+	},
+};
+module_platform_driver(pwm_loongson_driver);
+
+MODULE_DESCRIPTION("Loongson PWM driver");
+MODULE_AUTHOR("Loongson Technology Corporation Limited.");
+MODULE_LICENSE("GPL");
-- 
2.43.5

Re: [PATCH v5 0/2] pwm: Introduce pwm driver for the Loongson family chips

[Binbin Zhou]

On Wed, Jul 10, 2024 at 10:04 AM Binbin Zhou <zhoubinbin@loongson.cn> wrote:
>
> Hi all:
>
> This patchset introduce a generic PWM framework driver for Loongson family.
> Each PWM has one pulse width output signal and one pulse input signal to be measured.
>
> It can be found on Loongson-2K series cpus and Loongson LS7A bridge chips.
>
> Thanks.
>
> -------
> V5:
> patch (2/2):
>  - Rebase on pwm/for-next;
>  - Test with PWM_DEBUG enabled;
>  - Rewrote pwm_loongson_apply() and adjusted the order of pwm status and
>    polarity to avoid test failure;
>  - Added DIV64_U64_ROUND_UP in pwm_loongson_get_state() to avoid
>    precision loss and to avoid test failures.
>
> Link to V4:
> https://lore.kernel.org/all/cover.1716795485.git.zhoubinbin@loongson.cn/

Hi Uwe:

Sorry to interrupt.
I have tested the patchset on the pwm-next
branch(861a4272660ac0ff51aa4e2dbfbc3276c06b35eb) with PWM_DEBUG
enabled.
Please review it for me at your leisure.

Thanks.
Binbin
>
> V4:
> patch (2/2):
>  - Rebase on pwm/for-next;
>  - Addressed Uwe's review comments:
>    - Make use of devm_pwmchip_alloc() function;
>    - Add Limitations description;
>    - Add LOONGSON_ prefix for Loongson pwm register defines;
>    - Keep regs written only once;
>    - Rewrite duty/period calculation;
>    - Add dev_err_probe() in .probe();
>    - Fix some code style.
>
> Link to V3:
> https://lore.kernel.org/linux-pwm/cover.1713164810.git.zhoubinbin@loongson.cn/
>
> V3:
> patch (1/2):
>  - Add Reviewed-by tag from Krzysztof, thanks.
> patch (2/2):
>  - Several code stlye adjustments, such as line breaks.
>
> Link to V2:
> https://lore.kernel.org/all/cover.1712732719.git.zhoubinbin@loongson.cn/
>
> v2:
> - Remove the dts-related patches and update dts at once after all
> relevant drivers are complete.
> patch (1/2):
>  - The dt-binding filename should match compatible, rename it as
>    loongson,ls7a-pwm.yaml;
>  - Update binding description;
>  - Add description for each pwm cell;
>  - Drop '#pwm-cells' from required, for pwm.yaml makes it required already.
>
> Link to v1:
> https://lore.kernel.org/linux-pwm/cover.1711953223.git.zhoubinbin@loongson.cn/
>
> Binbin Zhou (2):
>   dt-bindings: pwm: Add Loongson PWM controller
>   pwm: Add Loongson PWM controller support
>
>  .../bindings/pwm/loongson,ls7a-pwm.yaml       |  66 ++++
>  MAINTAINERS                                   |   7 +
>  drivers/pwm/Kconfig                           |  12 +
>  drivers/pwm/Makefile                          |   1 +
>  drivers/pwm/pwm-loongson.c                    | 285 ++++++++++++++++++
>  5 files changed, 371 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/pwm/loongson,ls7a-pwm.yaml
>  create mode 100644 drivers/pwm/pwm-loongson.c
>
> --
> 2.43.5
>

Re: [PATCH v5 2/2] pwm: Add Loongson PWM controller support

[Uwe Kleine-König]

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Hello,

On Wed, Jul 10, 2024 at 10:04:07AM +0800, Binbin Zhou wrote:
> diff --git a/drivers/pwm/pwm-loongson.c b/drivers/pwm/pwm-loongson.c
> new file mode 100644
> index 000000000000..17ab2a2f48ad
> --- /dev/null
> +++ b/drivers/pwm/pwm-loongson.c
> @@ -0,0 +1,285 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Loongson PWM driver
> + *
> + * Author: Juxin Gao <gaojuxin@loongson.cn>
> + * Further cleanup and restructuring by:
> + *         Binbin Zhou <zhoubinbin@loongson.cn>
> + *
> + * Copyright (C) 2017-2024 Loongson Technology Corporation Limited.
> + *
> + * Limitations:
> + * - The buffer register value should be written before the CTRL register.
> + * - When disabled the output is driven to 0 independent of the configured
> + *   polarity.

An info about possible glitches and if a period is completed on
reconfiguration or when the PWM is disabled would be great.

Also if there is a publically available manual, please add a link here.

> + */
> +
> [...]
> +static int pwm_loongson_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> +			      const struct pwm_state *state)
> +{
> +	int ret;
> +	u64 period, duty_cycle;
> +	bool enabled = pwm->state.enabled;
> +
> +	if (enabled && !state->enabled) {
> +		pwm_loongson_disable(chip, pwm);
> +		return 0;
> +	}

You can also shortcut if !pwm->state.enabled. Something like:

	if (!state->enabled) {
		if (enabled)
			pwm_loongson_disable(chip, pwm);
		return 0;
	}

> +	if (state->polarity != pwm->state.polarity) {
> +		ret = pwm_loongson_set_polarity(chip, pwm, state->polarity);
> +		if (ret)
> +			return ret;
> +	}

Together with the shortcut above this is buggy. Consider:

	pwm_apply_might_sleep(mypwm, &(struct pwm_state){
			.period = A,
			.duty_cycle = B,
			.polarity = PWM_POLARITY_NORMAL,
			.enabled = true});
	pwm_apply_might_sleep(mypwm, &(struct pwm_state){
			.period = A,
			.duty_cycle = B,
			.polarity = PWM_POLARITY_INVERSED,
			.enabled = false});
	pwm_apply_might_sleep(mypwm, &(struct pwm_state){
			.period = A,
			.duty_cycle = B,
			.polarity = PWM_POLARITY_INVERSED,
			.enabled = true});

After the 2nd call you left pwm_loongson_apply() early without writing
the inversed polarity to the register space. In the 3rd call you have
state->polarity == pwm->state.polarity and so skip configuring the
polarity again.

I suggest to just do pwm_loongson_set_polarity() unconditionally if
state->enabled = true.

> +	period = min(state->period, NANOHZ_PER_HZ);
> +	duty_cycle = min(state->duty_cycle, NANOHZ_PER_HZ);
> +
> +	ret = pwm_loongson_config(chip, pwm, duty_cycle, period);
> +	if (ret)
> +		return ret;
> +
> +	if (!enabled && state->enabled)
> +		ret = pwm_loongson_enable(chip, pwm);
> +
> +	return ret;
> +}

Best regards
Uwe

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Re: [PATCH v5 2/2] pwm: Add Loongson PWM controller support

[Binbin Zhou]

Hi Uwe:

Thanks for your review.

On Tue, Sep 10, 2024 at 1:00 PM Uwe Kleine-König
<u.kleine-koenig@baylibre.com> wrote:
>
> Hello,
>
> On Wed, Jul 10, 2024 at 10:04:07AM +0800, Binbin Zhou wrote:
> > diff --git a/drivers/pwm/pwm-loongson.c b/drivers/pwm/pwm-loongson.c
> > new file mode 100644
> > index 000000000000..17ab2a2f48ad
> > --- /dev/null
> > +++ b/drivers/pwm/pwm-loongson.c
> > @@ -0,0 +1,285 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Loongson PWM driver
> > + *
> > + * Author: Juxin Gao <gaojuxin@loongson.cn>
> > + * Further cleanup and restructuring by:
> > + *         Binbin Zhou <zhoubinbin@loongson.cn>
> > + *
> > + * Copyright (C) 2017-2024 Loongson Technology Corporation Limited.
> > + *
> > + * Limitations:
> > + * - The buffer register value should be written before the CTRL register.
> > + * - When disabled the output is driven to 0 independent of the configured
> > + *   polarity.
>
> An info about possible glitches and if a period is completed on
> reconfiguration or when the PWM is disabled would be great.
>
> Also if there is a publically available manual, please add a link here.

The descriptions related to our PWM controllers are in the CPU
manuals, e.g. for the Loongson-2K series CPUs. but unfortunately we
only have the Chinese manuals right now, so I don't have a link to
them here.
>
> > + */
> > +
> > [...]
> > +static int pwm_loongson_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> > +                           const struct pwm_state *state)
> > +{
> > +     int ret;
> > +     u64 period, duty_cycle;
> > +     bool enabled = pwm->state.enabled;
> > +
> > +     if (enabled && !state->enabled) {
> > +             pwm_loongson_disable(chip, pwm);
> > +             return 0;
> > +     }
>
> You can also shortcut if !pwm->state.enabled. Something like:
>
>         if (!state->enabled) {
>                 if (enabled)
>                         pwm_loongson_disable(chip, pwm);
>                 return 0;
>         }
>
> > +     if (state->polarity != pwm->state.polarity) {
> > +             ret = pwm_loongson_set_polarity(chip, pwm, state->polarity);
> > +             if (ret)
> > +                     return ret;
> > +     }
>
> Together with the shortcut above this is buggy. Consider:
>
>         pwm_apply_might_sleep(mypwm, &(struct pwm_state){
>                         .period = A,
>                         .duty_cycle = B,
>                         .polarity = PWM_POLARITY_NORMAL,
>                         .enabled = true});
>         pwm_apply_might_sleep(mypwm, &(struct pwm_state){
>                         .period = A,
>                         .duty_cycle = B,
>                         .polarity = PWM_POLARITY_INVERSED,
>                         .enabled = false});
>         pwm_apply_might_sleep(mypwm, &(struct pwm_state){
>                         .period = A,
>                         .duty_cycle = B,
>                         .polarity = PWM_POLARITY_INVERSED,
>                         .enabled = true});
>
> After the 2nd call you left pwm_loongson_apply() early without writing
> the inversed polarity to the register space. In the 3rd call you have
> state->polarity == pwm->state.polarity and so skip configuring the
> polarity again.
>
> I suggest to just do pwm_loongson_set_polarity() unconditionally if
> state->enabled = true.

I check code and try to do it like:

        if (!state->enabled) {
                if (enabled)
                        pwm_loongson_disable(chip, pwm);
                return 0;
        }

        ret = pwm_loongson_set_polarity(chip, pwm, state->polarity);
        if (ret)
                return ret;

Thanks.
Binbin
>
> > +     period = min(state->period, NANOHZ_PER_HZ);
> > +     duty_cycle = min(state->duty_cycle, NANOHZ_PER_HZ);
> > +
> > +     ret = pwm_loongson_config(chip, pwm, duty_cycle, period);
> > +     if (ret)
> > +             return ret;
> > +
> > +     if (!enabled && state->enabled)
> > +             ret = pwm_loongson_enable(chip, pwm);
> > +
> > +     return ret;
> > +}
>
> Best regards
> Uwe