[PATCH v13 1/2] Add DT bindings YAML schema for PWM fan controller of LGM SoC

[PATCH v13 1/2] Add DT bindings YAML schema for PWM fan controller of LGM SoC

[Rahul Tanwar]

Intel's LGM(Lightning Mountain) SoC contains a PWM fan controller
which is only used to control the fan attached to the system. This
PWM controller does not have any other consumer other than fan.
Add DT bindings documentation for this PWM fan controller.

Signed-off-by: Rahul Tanwar <rahul.tanwar@linux.intel.com>
Reviewed-by: Rob Herring <robh@kernel.org>
---
 .../devicetree/bindings/pwm/intel,lgm-pwm.yaml     | 44 ++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/pwm/intel,lgm-pwm.yaml

diff --git a/Documentation/devicetree/bindings/pwm/intel,lgm-pwm.yaml b/Documentation/devicetree/bindings/pwm/intel,lgm-pwm.yaml
new file mode 100644
index 000000000000..11a606536169
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/intel,lgm-pwm.yaml
@@ -0,0 +1,44 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pwm/intel,lgm-pwm.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: LGM SoC PWM fan controller
+
+maintainers:
+  - Rahul Tanwar <rtanwar@maxlinear.com>
+
+properties:
+  compatible:
+    const: intel,lgm-pwm
+
+  reg:
+    maxItems: 1
+
+  "#pwm-cells":
+    const: 2
+
+  clocks:
+    maxItems: 1
+
+  resets:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - resets
+
+additionalProperties: false
+
+examples:
+  - |
+    pwm: pwm@e0d00000 {
+        compatible = "intel,lgm-pwm";
+        reg = <0xe0d00000 0x30>;
+        #pwm-cells = <2>;
+        clocks = <&cgu0 126>;
+        resets = <&rcu0 0x30 21>;
+    };
-- 
2.11.0

[PATCH v13 2/2] Add PWM fan controller driver for LGM SoC

[Rahul Tanwar]

Intel Lightning Mountain(LGM) SoC contains a PWM fan controller.
This PWM controller does not have any other consumer, it is a
dedicated PWM controller for fan attached to the system. Add
driver for this PWM fan controller.

Signed-off-by: Rahul Tanwar <rahul.tanwar@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
---
 drivers/pwm/Kconfig         |  11 ++
 drivers/pwm/Makefile        |   1 +
 drivers/pwm/pwm-intel-lgm.c | 246 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 258 insertions(+)
 create mode 100644 drivers/pwm/pwm-intel-lgm.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 7dbcf6973d33..4949c51fe90b 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -232,6 +232,17 @@ config PWM_IMX_TPM
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-imx-tpm.
 
+config PWM_INTEL_LGM
+	tristate "Intel LGM PWM support"
+	depends on HAS_IOMEM
+	depends on (OF && X86) || COMPILE_TEST
+	select REGMAP_MMIO
+	help
+	  Generic PWM fan controller driver for LGM SoC.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-intel-lgm.
+
 config PWM_IQS620A
 	tristate "Azoteq IQS620A PWM support"
 	depends on MFD_IQS62X || COMPILE_TEST
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 2c2ba0a03557..e9431b151694 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -20,6 +20,7 @@ obj-$(CONFIG_PWM_IMG)		+= pwm-img.o
 obj-$(CONFIG_PWM_IMX1)		+= pwm-imx1.o
 obj-$(CONFIG_PWM_IMX27)		+= pwm-imx27.o
 obj-$(CONFIG_PWM_IMX_TPM)	+= pwm-imx-tpm.o
+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_LP3943)	+= pwm-lp3943.o
diff --git a/drivers/pwm/pwm-intel-lgm.c b/drivers/pwm/pwm-intel-lgm.c
new file mode 100644
index 000000000000..ea3df75a5971
--- /dev/null
+++ b/drivers/pwm/pwm-intel-lgm.c
@@ -0,0 +1,246 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020 Intel Corporation.
+ *
+ * Limitations:
+ * - The hardware supports fixed period which is dependent on 2/3 or 4
+ *   wire fan mode.
+ * - Supports normal polarity. Does not support changing polarity.
+ * - When PWM is disabled, output of PWM will become 0(inactive). It doesn't
+ *   keep track of running period.
+ * - When duty cycle is changed, PWM output may be a mix of previous setting
+ *   and new setting for the first period. From second period, the output is
+ *   based on new setting.
+ * - It is a dedicated PWM fan controller. There are no other consumers for
+ *   this PWM controller.
+ */
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/mod_devicetable.h>
+#include <linux/pwm.h>
+#include <linux/regmap.h>
+#include <linux/reset.h>
+
+#define LGM_PWM_FAN_CON0		0x0
+#define LGM_PWM_FAN_EN_EN		BIT(0)
+#define LGM_PWM_FAN_EN_DIS		0x0
+#define LGM_PWM_FAN_EN_MSK		BIT(0)
+#define LGM_PWM_FAN_MODE_2WIRE		0x0
+#define LGM_PWM_FAN_MODE_MSK		BIT(1)
+#define LGM_PWM_FAN_DC_MSK		GENMASK(23, 16)
+
+#define LGM_PWM_FAN_CON1		0x4
+#define LGM_PWM_FAN_MAX_RPM_MSK		GENMASK(15, 0)
+
+#define LGM_PWM_MAX_RPM			(BIT(16) - 1)
+#define LGM_PWM_DEFAULT_RPM		4000
+#define LGM_PWM_MAX_DUTY_CYCLE		(BIT(8) - 1)
+
+#define LGM_PWM_DC_BITS			8
+
+#define LGM_PWM_PERIOD_2WIRE_NS		(40 * NSEC_PER_MSEC)
+
+struct lgm_pwm_chip {
+	struct pwm_chip chip;
+	struct regmap *regmap;
+	struct clk *clk;
+	struct reset_control *rst;
+	u32 period;
+};
+
+static inline struct lgm_pwm_chip *to_lgm_pwm_chip(struct pwm_chip *chip)
+{
+	return container_of(chip, struct lgm_pwm_chip, chip);
+}
+
+static int lgm_pwm_enable(struct pwm_chip *chip, bool enable)
+{
+	struct lgm_pwm_chip *pc = to_lgm_pwm_chip(chip);
+	struct regmap *regmap = pc->regmap;
+
+	return regmap_update_bits(regmap, LGM_PWM_FAN_CON0, LGM_PWM_FAN_EN_MSK,
+				  enable ? LGM_PWM_FAN_EN_EN : LGM_PWM_FAN_EN_DIS);
+}
+
+static int lgm_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			 const struct pwm_state *state)
+{
+	struct lgm_pwm_chip *pc = to_lgm_pwm_chip(chip);
+	u32 duty_cycle, val;
+	int ret;
+
+	/* The hardware only supports normal polarity and fixed period. */
+	if (state->polarity != PWM_POLARITY_NORMAL || state->period < pc->period)
+		return -EINVAL;
+
+	if (!state->enabled)
+		return lgm_pwm_enable(chip, 0);
+
+	duty_cycle = min_t(u64, state->duty_cycle, pc->period);
+	val = duty_cycle * LGM_PWM_MAX_DUTY_CYCLE / pc->period;
+
+	ret = regmap_update_bits(pc->regmap, LGM_PWM_FAN_CON0, LGM_PWM_FAN_DC_MSK,
+				 FIELD_PREP(LGM_PWM_FAN_DC_MSK, val));
+	if (ret)
+		return ret;
+
+	return lgm_pwm_enable(chip, 1);
+}
+
+static void lgm_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+			      struct pwm_state *state)
+{
+	struct lgm_pwm_chip *pc = to_lgm_pwm_chip(chip);
+	u32 duty, val;
+
+	state->enabled = regmap_test_bits(pc->regmap, LGM_PWM_FAN_CON0,
+					  LGM_PWM_FAN_EN_EN);
+	state->polarity = PWM_POLARITY_NORMAL;
+	state->period = pc->period; /* fixed period */
+
+	regmap_read(pc->regmap, LGM_PWM_FAN_CON0, &val);
+	duty = FIELD_GET(LGM_PWM_FAN_DC_MSK, val);
+	state->duty_cycle = DIV_ROUND_UP(duty * pc->period, LGM_PWM_MAX_DUTY_CYCLE);
+}
+
+static const struct pwm_ops lgm_pwm_ops = {
+	.get_state = lgm_pwm_get_state,
+	.apply = lgm_pwm_apply,
+	.owner = THIS_MODULE,
+};
+
+static void lgm_pwm_init(struct lgm_pwm_chip *pc)
+{
+	struct regmap *regmap = pc->regmap;
+	u32 con0_val;
+
+	con0_val = FIELD_PREP(LGM_PWM_FAN_MODE_MSK, LGM_PWM_FAN_MODE_2WIRE);
+	pc->period = LGM_PWM_PERIOD_2WIRE_NS;
+	regmap_update_bits(regmap, LGM_PWM_FAN_CON1, LGM_PWM_FAN_MAX_RPM_MSK,
+			   LGM_PWM_DEFAULT_RPM);
+	regmap_update_bits(regmap, LGM_PWM_FAN_CON0, LGM_PWM_FAN_MODE_MSK,
+			   con0_val);
+}
+
+static const struct regmap_config lgm_pwm_regmap_config = {
+	.reg_bits = 32,
+	.reg_stride = 4,
+	.val_bits = 32,
+};
+
+static void lgm_clk_disable(void *data)
+{
+	struct lgm_pwm_chip *pc = data;
+
+	clk_disable_unprepare(pc->clk);
+}
+
+static int lgm_clk_enable(struct device *dev, struct lgm_pwm_chip *pc)
+{
+	int ret;
+
+	ret = clk_prepare_enable(pc->clk);
+	if (ret)
+		return ret;
+
+	return devm_add_action_or_reset(dev, lgm_clk_disable, pc);
+}
+
+static void lgm_reset_control_assert(void *data)
+{
+	struct lgm_pwm_chip *pc = data;
+
+	reset_control_assert(pc->rst);
+}
+
+static int lgm_reset_control_deassert(struct device *dev, struct lgm_pwm_chip *pc)
+{
+	int ret;
+
+	ret = reset_control_deassert(pc->rst);
+	if (ret)
+		return ret;
+
+	return devm_add_action_or_reset(dev, lgm_reset_control_assert, pc);
+}
+
+static int lgm_pwm_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct lgm_pwm_chip *pc;
+	void __iomem *io_base;
+	int ret;
+
+	pc = devm_kzalloc(dev, sizeof(*pc), GFP_KERNEL);
+	if (!pc)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, pc);
+
+	io_base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(io_base))
+		return PTR_ERR(io_base);
+
+	pc->regmap = devm_regmap_init_mmio(dev, io_base, &lgm_pwm_regmap_config);
+	if (IS_ERR(pc->regmap))
+		return dev_err_probe(dev, PTR_ERR(pc->regmap),
+				     "failed to init register map\n");
+
+	pc->clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(pc->clk))
+		return dev_err_probe(dev, PTR_ERR(pc->clk), "failed to get clock\n");
+
+	ret = lgm_clk_enable(dev, pc);
+	if (ret) {
+		dev_err(dev, "failed to enable clock\n");
+		return ret;
+	}
+
+	pc->rst = devm_reset_control_get_exclusive(dev, NULL);
+	if (IS_ERR(pc->rst))
+		return dev_err_probe(dev, PTR_ERR(pc->rst),
+				     "failed to get reset control\n");
+
+	ret = lgm_reset_control_deassert(dev, pc);
+	if (ret)
+		return dev_err_probe(dev, ret, "cannot deassert reset control\n");
+
+	pc->chip.dev = dev;
+	pc->chip.ops = &lgm_pwm_ops;
+	pc->chip.npwm = 1;
+
+	lgm_pwm_init(pc);
+
+	ret = pwmchip_add(&pc->chip);
+	if (ret < 0) {
+		dev_err(dev, "failed to add PWM chip: %pe\n", ERR_PTR(ret));
+		return ret;
+	}
+
+	return 0;
+}
+
+static int lgm_pwm_remove(struct platform_device *pdev)
+{
+	struct lgm_pwm_chip *pc = platform_get_drvdata(pdev);
+
+	return pwmchip_remove(&pc->chip);
+}
+
+static const struct of_device_id lgm_pwm_of_match[] = {
+	{ .compatible = "intel,lgm-pwm" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, lgm_pwm_of_match);
+
+static struct platform_driver lgm_pwm_driver = {
+	.driver = {
+		.name = "intel-pwm",
+		.of_match_table = lgm_pwm_of_match,
+	},
+	.probe = lgm_pwm_probe,
+	.remove = lgm_pwm_remove,
+};
+module_platform_driver(lgm_pwm_driver);
-- 
2.11.0

Re: [PATCH v13 2/2] Add PWM fan controller driver for LGM SoC

[Uwe Kleine-König]

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Hello,

(hhm Thierry already announced to have taken this patch, so my review is
late.)

On Tue, Sep 15, 2020 at 04:23:37PM +0800, Rahul Tanwar wrote:
> Intel Lightning Mountain(LGM) SoC contains a PWM fan controller.
> This PWM controller does not have any other consumer, it is a
> dedicated PWM controller for fan attached to the system. Add
> driver for this PWM fan controller.
> 
> Signed-off-by: Rahul Tanwar <rahul.tanwar@linux.intel.com>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
> ---
>  drivers/pwm/Kconfig         |  11 ++
>  drivers/pwm/Makefile        |   1 +
>  drivers/pwm/pwm-intel-lgm.c | 246 ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 258 insertions(+)
>  create mode 100644 drivers/pwm/pwm-intel-lgm.c
> 
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index 7dbcf6973d33..4949c51fe90b 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -232,6 +232,17 @@ config PWM_IMX_TPM
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called pwm-imx-tpm.
>  
> +config PWM_INTEL_LGM
> +	tristate "Intel LGM PWM support"
> +	depends on HAS_IOMEM
> +	depends on (OF && X86) || COMPILE_TEST
> +	select REGMAP_MMIO
> +	help
> +	  Generic PWM fan controller driver for LGM SoC.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called pwm-intel-lgm.
> +
>  config PWM_IQS620A
>  	tristate "Azoteq IQS620A PWM support"
>  	depends on MFD_IQS62X || COMPILE_TEST
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index 2c2ba0a03557..e9431b151694 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -20,6 +20,7 @@ obj-$(CONFIG_PWM_IMG)		+= pwm-img.o
>  obj-$(CONFIG_PWM_IMX1)		+= pwm-imx1.o
>  obj-$(CONFIG_PWM_IMX27)		+= pwm-imx27.o
>  obj-$(CONFIG_PWM_IMX_TPM)	+= pwm-imx-tpm.o
> +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_LP3943)	+= pwm-lp3943.o
> diff --git a/drivers/pwm/pwm-intel-lgm.c b/drivers/pwm/pwm-intel-lgm.c
> new file mode 100644
> index 000000000000..ea3df75a5971
> --- /dev/null
> +++ b/drivers/pwm/pwm-intel-lgm.c
> @@ -0,0 +1,246 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2020 Intel Corporation.
> + *
> + * Limitations:
> + * - The hardware supports fixed period which is dependent on 2/3 or 4
> + *   wire fan mode.

The driver now hardcodes 2-wire mode. IMHO that is worth mentioning.

> +static void lgm_clk_disable(void *data)
> +{
> +	struct lgm_pwm_chip *pc = data;
> +
> +	clk_disable_unprepare(pc->clk);
> +}
> +
> +static int lgm_clk_enable(struct device *dev, struct lgm_pwm_chip *pc)
> +{
> +	int ret;
> +
> +	ret = clk_prepare_enable(pc->clk);
> +	if (ret)
> +		return ret;
> +
> +	return devm_add_action_or_reset(dev, lgm_clk_disable, pc);
> +}

My first reflex here was to point out that lgm_clk_disable() isn't the
counter part to lgm_clk_enable() and so lgm_clk_disable() needs
adaption. On a second look this is correct and so I think the function
names are wrong. The usual naming would be to use _release instead of
_disable. Having said that the enable function could be named
devm_clk_enable and live in drivers/clk/clk-devres.c. (Or
devm_clk_get_enabled()?)

> +static void lgm_reset_control_assert(void *data)
> +{
> +	struct lgm_pwm_chip *pc = data;
> +
> +	reset_control_assert(pc->rst);
> +}
> +
> +static int lgm_reset_control_deassert(struct device *dev, struct lgm_pwm_chip *pc)
> +{
> +	int ret;
> +
> +	ret = reset_control_deassert(pc->rst);
> +	if (ret)
> +		return ret;
> +
> +	return devm_add_action_or_reset(dev, lgm_reset_control_assert, pc);
> +}

A similar comment applies here.

> +static int lgm_pwm_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct lgm_pwm_chip *pc;
> +	void __iomem *io_base;
> +	int ret;
> +
> +	pc = devm_kzalloc(dev, sizeof(*pc), GFP_KERNEL);
> +	if (!pc)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, pc);
> +
> +	io_base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(io_base))
> +		return PTR_ERR(io_base);
> +
> +	pc->regmap = devm_regmap_init_mmio(dev, io_base, &lgm_pwm_regmap_config);
> +	if (IS_ERR(pc->regmap))
> +		return dev_err_probe(dev, PTR_ERR(pc->regmap),
> +				     "failed to init register map\n");
> +
> +	pc->clk = devm_clk_get(dev, NULL);
> +	if (IS_ERR(pc->clk))
> +		return dev_err_probe(dev, PTR_ERR(pc->clk), "failed to get clock\n");
> +
> +	ret = lgm_clk_enable(dev, pc);
> +	if (ret) {
> +		dev_err(dev, "failed to enable clock\n");

You used dev_err_probe four times for six error paths. I wonder why you
didn't use it here (and below for a failing pwmchip_add()).

> +		return ret;
> +	}
> +
> +	pc->rst = devm_reset_control_get_exclusive(dev, NULL);
> +	if (IS_ERR(pc->rst))
> +		return dev_err_probe(dev, PTR_ERR(pc->rst),
> +				     "failed to get reset control\n");
> +
> +	ret = lgm_reset_control_deassert(dev, pc);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "cannot deassert reset control\n");

After lgm_reset_control_deassert is called pc->rst is unused. So there
is no need to have this member in struct lgm_pwm_chip. The same applies
to ->clk. (You have to pass rst (or clk) to devm_add_action_or_reset for
that to work. Looks like a nice idea anyhow.)

> +	pc->chip.dev = dev;
> +	pc->chip.ops = &lgm_pwm_ops;
> +	pc->chip.npwm = 1;

pc->chip.base should probably be set to -1.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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Re: [PATCH v13 2/2] Add PWM fan controller driver for LGM SoC

[Thierry Reding]

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On Thu, Sep 24, 2020 at 08:55:34AM +0200, Uwe Kleine-König wrote:
> Hello,
> 
> (hhm Thierry already announced to have taken this patch, so my review is
> late.)

There's also a build warning in linux-next caused by this patch, so I'm
going to back it out.

Rahul, please address Uwe's comments and make sure to fix the build
warning as well.

Thierry

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Re: [PATCH v13 2/2] Add PWM fan controller driver for LGM SoC

[Tanwar, Rahul]

On 24/9/2020 3:12 pm, Thierry Reding wrote:
> On Thu, Sep 24, 2020 at 08:55:34AM +0200, Uwe Kleine-König wrote:
>> Hello,
>>
>> (hhm Thierry already announced to have taken this patch, so my review is
>> late.)
> There's also a build warning in linux-next caused by this patch, so I'm
> going to back it out.
>
> Rahul, please address Uwe's comments and make sure to fix the build
> warning as well.

Well noted, will do.

Regards,
Rahul

> Thierry

Re: [PATCH v13 2/2] Add PWM fan controller driver for LGM SoC

[Andy Shevchenko]

On Thu, Sep 24, 2020 at 08:55:34AM +0200, Uwe Kleine-König wrote:
> On Tue, Sep 15, 2020 at 04:23:37PM +0800, Rahul Tanwar wrote:

...

> > +	ret = lgm_clk_enable(dev, pc);
> > +	if (ret) {
> > +		dev_err(dev, "failed to enable clock\n");
> 
> You used dev_err_probe four times for six error paths. I wonder why you
> didn't use it here (and below for a failing pwmchip_add()).

dev_err_probe() makes sense when we might experience deferred probe. In neither
of mentioned function this can be the case.

> > +		return ret;
> > +	}

...

> > +	ret = lgm_reset_control_deassert(dev, pc);
> > +	if (ret)
> > +		return dev_err_probe(dev, ret, "cannot deassert reset control\n");
> 
> After lgm_reset_control_deassert is called pc->rst is unused. So there
> is no need to have this member in struct lgm_pwm_chip. The same applies
> to ->clk. (You have to pass rst (or clk) to devm_add_action_or_reset for
> that to work. Looks like a nice idea anyhow.)

True. And above dev_err_probe() is not needed.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v13 2/2] Add PWM fan controller driver for LGM SoC

[Uwe Kleine-König]

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On Thu, Sep 24, 2020 at 04:23:34PM +0300, Andy Shevchenko wrote:
> On Thu, Sep 24, 2020 at 08:55:34AM +0200, Uwe Kleine-König wrote:
> > On Tue, Sep 15, 2020 at 04:23:37PM +0800, Rahul Tanwar wrote:
> 
> ...
> 
> > > +	ret = lgm_clk_enable(dev, pc);
> > > +	if (ret) {
> > > +		dev_err(dev, "failed to enable clock\n");
> > 
> > You used dev_err_probe four times for six error paths. I wonder why you
> > didn't use it here (and below for a failing pwmchip_add()).
> 
> dev_err_probe() makes sense when we might experience deferred probe. In neither
> of mentioned function this can be the case.
> 
> > > +		return ret;
> > > +	}
> 
> ...
> 
> > > +	ret = lgm_reset_control_deassert(dev, pc);
> > > +	if (ret)
> > > +		return dev_err_probe(dev, ret, "cannot deassert reset control\n");
> > 
> > After lgm_reset_control_deassert is called pc->rst is unused. So there
> > is no need to have this member in struct lgm_pwm_chip. The same applies
> > to ->clk. (You have to pass rst (or clk) to devm_add_action_or_reset for
> > that to work. Looks like a nice idea anyhow.)
> 
> True. And above dev_err_probe() is not needed.

You argue that dev_err_probe() gives no benefit as
lgm_reset_control_deassert won't return -EPROBE_DEFER, right?

Still I consider it a useful function because

 a) I (as an author or as a reviewer) don't need to think if the
    failing function might return -EPROBE_DEFER now or in the future.
    dev_err_probe does the right thing even for functions that don't
    return -EPROBE_DEFER.

 b) With dev_err_probe() I can accomplish things in a single line that
    need two lines when open coding it.

 c) dev_err_probe() emits the symbolic error name without having to
    resort to %pe + ERR_PTR.

 d) Using dev_err_probe() for all error paths gives a consistency that I
    like with a maintainer's hat on.

So I still want to request using dev_err_probe() in all error paths.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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Re: [PATCH v13 2/2] Add PWM fan controller driver for LGM SoC

[Andy Shevchenko]

On Thu, Sep 24, 2020 at 04:16:59PM +0200, Uwe Kleine-König wrote:
> On Thu, Sep 24, 2020 at 04:23:34PM +0300, Andy Shevchenko wrote:
> > On Thu, Sep 24, 2020 at 08:55:34AM +0200, Uwe Kleine-König wrote:

...

> > True. And above dev_err_probe() is not needed.
> 
> You argue that dev_err_probe() gives no benefit as
> lgm_reset_control_deassert won't return -EPROBE_DEFER, right?
> 
> Still I consider it a useful function because
> 
>  a) I (as an author or as a reviewer) don't need to think if the
>     failing function might return -EPROBE_DEFER now or in the future.
>     dev_err_probe does the right thing even for functions that don't
>     return -EPROBE_DEFER.
> 
>  b) With dev_err_probe() I can accomplish things in a single line that
>     need two lines when open coding it.
> 
>  c) dev_err_probe() emits the symbolic error name without having to
>     resort to %pe + ERR_PTR.
> 
>  d) Using dev_err_probe() for all error paths gives a consistency that I
>     like with a maintainer's hat on.
> 
> So I still want to request using dev_err_probe() in all error paths.

As a maintainer it is your choice. I really would like to see more consensus
among maintainers, some are insisting of what I said, some, like you, on the
opposite, some hate that API and some simply don't care.

And on top of that I saw already use of API without taking returned value into
account.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v13 2/2] Add PWM fan controller driver for LGM SoC

[Thierry Reding]

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On Thu, Sep 24, 2020 at 04:16:59PM +0200, Uwe Kleine-König wrote:
> On Thu, Sep 24, 2020 at 04:23:34PM +0300, Andy Shevchenko wrote:
> > On Thu, Sep 24, 2020 at 08:55:34AM +0200, Uwe Kleine-König wrote:
> > > On Tue, Sep 15, 2020 at 04:23:37PM +0800, Rahul Tanwar wrote:
> > 
> > ...
> > 
> > > > +	ret = lgm_clk_enable(dev, pc);
> > > > +	if (ret) {
> > > > +		dev_err(dev, "failed to enable clock\n");
> > > 
> > > You used dev_err_probe four times for six error paths. I wonder why you
> > > didn't use it here (and below for a failing pwmchip_add()).
> > 
> > dev_err_probe() makes sense when we might experience deferred probe. In neither
> > of mentioned function this can be the case.
> > 
> > > > +		return ret;
> > > > +	}
> > 
> > ...
> > 
> > > > +	ret = lgm_reset_control_deassert(dev, pc);
> > > > +	if (ret)
> > > > +		return dev_err_probe(dev, ret, "cannot deassert reset control\n");
> > > 
> > > After lgm_reset_control_deassert is called pc->rst is unused. So there
> > > is no need to have this member in struct lgm_pwm_chip. The same applies
> > > to ->clk. (You have to pass rst (or clk) to devm_add_action_or_reset for
> > > that to work. Looks like a nice idea anyhow.)
> > 
> > True. And above dev_err_probe() is not needed.
> 
> You argue that dev_err_probe() gives no benefit as
> lgm_reset_control_deassert won't return -EPROBE_DEFER, right?
> 
> Still I consider it a useful function because
> 
>  a) I (as an author or as a reviewer) don't need to think if the
>     failing function might return -EPROBE_DEFER now or in the future.
>     dev_err_probe does the right thing even for functions that don't
>     return -EPROBE_DEFER.
> 
>  b) With dev_err_probe() I can accomplish things in a single line that
>     need two lines when open coding it.
> 
>  c) dev_err_probe() emits the symbolic error name without having to
>     resort to %pe + ERR_PTR.
> 
>  d) Using dev_err_probe() for all error paths gives a consistency that I
>     like with a maintainer's hat on.

That would perhaps be true if all error paths did use dev_err_probe().
And even if that were the case, dev_err_probe() doesn't guarantee that
error messages will actually be consistent because developers can still
provide whatever format string they like.

Also, the format of the messages that dev_err_probe() prints is unlike
anything that I've seen, so introducing dev_err_probe() actually makes
things more inconsistent, in my opinion.

I have in fact been advocating for people to use error messages of the
form:

	"failed to ...: %d\n", err

or:

	"unable to ...: %d\n", err

Or some other similar form because that's the most common type that I
have come across in the kernel. I think it's also easier to read those
error messages because they contain the important data (i.e. the
description, which tells you what went wrong) first and then are
followed by the error code (which tells you how it failed).

Now I suspect the current format was chosen because we need to have the
constant part first, because otherwise the arbitrary format string could
be something that doesn't lend itself to have an error code appended.

The current format is arguably also something that's easier to parse
from some script because the format is in a somewhat standard format. On
the other hand, I think this is a bit misguided because we already have
structured log messages, so I wonder if it might have been better to
make the error code part of structured log messages to make them truly
machine readable but leave the formatting up to developers so that they
can use whatever is consistent within the driver or whatever fits best
without actually adding a standard string to the log messages.

Thierry

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Re: [PATCH v13 2/2] Add PWM fan controller driver for LGM SoC

[Tanwar, Rahul]

Hi Uwe,

Thanks for review & feedback.

On 24/9/2020 2:55 pm, Uwe Kleine-König wrote:
> Hello,
>
> (hhm Thierry already announced to have taken this patch, so my review is
> late.)
>
> On Tue, Sep 15, 2020 at 04:23:37PM +0800, Rahul Tanwar wrote:
>> Intel Lightning Mountain(LGM) SoC contains a PWM fan controller.
>> This PWM controller does not have any other consumer, it is a
>> dedicated PWM controller for fan attached to the system. Add
>> driver for this PWM fan controller.
>>
>> Signed-off-by: Rahul Tanwar <rahul.tanwar@linux.intel.com>
>> Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
>> ---
>>  drivers/pwm/Kconfig         |  11 ++
>>  drivers/pwm/Makefile        |   1 +
>>  drivers/pwm/pwm-intel-lgm.c | 246 ++++++++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 258 insertions(+)
>>  create mode 100644 drivers/pwm/pwm-intel-lgm.c
>>
>> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
>> index 7dbcf6973d33..4949c51fe90b 100644
>> --- a/drivers/pwm/Kconfig
>> +++ b/drivers/pwm/Kconfig
>> @@ -232,6 +232,17 @@ config PWM_IMX_TPM
>>  	  To compile this driver as a module, choose M here: the module
>>  	  will be called pwm-imx-tpm.
>>  
>> +config PWM_INTEL_LGM
>> +	tristate "Intel LGM PWM support"
>> +	depends on HAS_IOMEM
>> +	depends on (OF && X86) || COMPILE_TEST
>> +	select REGMAP_MMIO
>> +	help
>> +	  Generic PWM fan controller driver for LGM SoC.
>> +
>> +	  To compile this driver as a module, choose M here: the module
>> +	  will be called pwm-intel-lgm.
>> +
>>  config PWM_IQS620A
>>  	tristate "Azoteq IQS620A PWM support"
>>  	depends on MFD_IQS62X || COMPILE_TEST
>> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
>> index 2c2ba0a03557..e9431b151694 100644
>> --- a/drivers/pwm/Makefile
>> +++ b/drivers/pwm/Makefile
>> @@ -20,6 +20,7 @@ obj-$(CONFIG_PWM_IMG)		+= pwm-img.o
>>  obj-$(CONFIG_PWM_IMX1)		+= pwm-imx1.o
>>  obj-$(CONFIG_PWM_IMX27)		+= pwm-imx27.o
>>  obj-$(CONFIG_PWM_IMX_TPM)	+= pwm-imx-tpm.o
>> +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_LP3943)	+= pwm-lp3943.o
>> diff --git a/drivers/pwm/pwm-intel-lgm.c b/drivers/pwm/pwm-intel-lgm.c
>> new file mode 100644
>> index 000000000000..ea3df75a5971
>> --- /dev/null
>> +++ b/drivers/pwm/pwm-intel-lgm.c
>> @@ -0,0 +1,246 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (C) 2020 Intel Corporation.
>> + *
>> + * Limitations:
>> + * - The hardware supports fixed period which is dependent on 2/3 or 4
>> + *   wire fan mode.
> The driver now hardcodes 2-wire mode. IMHO that is worth mentioning.

Will update.

>> +static void lgm_clk_disable(void *data)
>> +{
>> +	struct lgm_pwm_chip *pc = data;
>> +
>> +	clk_disable_unprepare(pc->clk);
>> +}
>> +
>> +static int lgm_clk_enable(struct device *dev, struct lgm_pwm_chip *pc)
>> +{
>> +	int ret;
>> +
>> +	ret = clk_prepare_enable(pc->clk);
>> +	if (ret)
>> +		return ret;
>> +
>> +	return devm_add_action_or_reset(dev, lgm_clk_disable, pc);
>> +}
> My first reflex here was to point out that lgm_clk_disable() isn't the
> counter part to lgm_clk_enable() and so lgm_clk_disable() needs
> adaption. On a second look this is correct and so I think the function
> names are wrong. The usual naming would be to use _release instead of
> _disable. Having said that the enable function could be named
> devm_clk_enable and live in drivers/clk/clk-devres.c. (Or
> devm_clk_get_enabled()?)


Will change function name from _disable to _release. But i think addition
of a generic devm_clk_enable in drivers/clk/clk-devres.c can be taken as
a separate task in a future patch (not clubbed with this driver)..


>> +static void lgm_reset_control_assert(void *data)
>> +{
>> +	struct lgm_pwm_chip *pc = data;
>> +
>> +	reset_control_assert(pc->rst);
>> +}
>> +
>> +static int lgm_reset_control_deassert(struct device *dev, struct lgm_pwm_chip *pc)
>> +{
>> +	int ret;
>> +
>> +	ret = reset_control_deassert(pc->rst);
>> +	if (ret)
>> +		return ret;
>> +
>> +	return devm_add_action_or_reset(dev, lgm_reset_control_assert, pc);
>> +}
> A similar comment applies here.
>
>> +static int lgm_pwm_probe(struct platform_device *pdev)
>> +{
>> +	struct device *dev = &pdev->dev;
>> +	struct lgm_pwm_chip *pc;
>> +	void __iomem *io_base;
>> +	int ret;
>> +
>> +	pc = devm_kzalloc(dev, sizeof(*pc), GFP_KERNEL);
>> +	if (!pc)
>> +		return -ENOMEM;
>> +
>> +	platform_set_drvdata(pdev, pc);
>> +
>> +	io_base = devm_platform_ioremap_resource(pdev, 0);
>> +	if (IS_ERR(io_base))
>> +		return PTR_ERR(io_base);
>> +
>> +	pc->regmap = devm_regmap_init_mmio(dev, io_base, &lgm_pwm_regmap_config);
>> +	if (IS_ERR(pc->regmap))
>> +		return dev_err_probe(dev, PTR_ERR(pc->regmap),
>> +				     "failed to init register map\n");
>> +
>> +	pc->clk = devm_clk_get(dev, NULL);
>> +	if (IS_ERR(pc->clk))
>> +		return dev_err_probe(dev, PTR_ERR(pc->clk), "failed to get clock\n");
>> +
>> +	ret = lgm_clk_enable(dev, pc);
>> +	if (ret) {
>> +		dev_err(dev, "failed to enable clock\n");
> You used dev_err_probe four times for six error paths. I wonder why you
> didn't use it here (and below for a failing pwmchip_add()).

Well noted, will update.

>> +		return ret;
>> +	}
>> +
>> +	pc->rst = devm_reset_control_get_exclusive(dev, NULL);
>> +	if (IS_ERR(pc->rst))
>> +		return dev_err_probe(dev, PTR_ERR(pc->rst),
>> +				     "failed to get reset control\n");
>> +
>> +	ret = lgm_reset_control_deassert(dev, pc);
>> +	if (ret)
>> +		return dev_err_probe(dev, ret, "cannot deassert reset control\n");
> After lgm_reset_control_deassert is called pc->rst is unused. So there
> is no need to have this member in struct lgm_pwm_chip. The same applies
> to ->clk. (You have to pass rst (or clk) to devm_add_action_or_reset for
> that to work. Looks like a nice idea anyhow.)

Agreed, will update.

>> +	pc->chip.dev = dev;
>> +	pc->chip.ops = &lgm_pwm_ops;
>> +	pc->chip.npwm = 1;
> pc->chip.base should probably be set to -1.

Got it, will update. Thanks.

Regards,
Rahul

> Best regards
> Uwe
>

Re: [PATCH v13 0/2] pwm: intel: Add PWM driver for a new SoC

[Thierry Reding]

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On Tue, Sep 15, 2020 at 04:23:35PM +0800, Rahul Tanwar wrote:
> Patch 1 adds dt binding document in YAML format.
> Patch 2 add PWM fan controller driver for LGM SoC.
> 
> v13:
> - Address below review concerns (Philipp Zabel)
>  * Make unnecessary 2 line comment as 1 line comment.
>  * Move reset_deassert at the last after clk_enable.
>  * Remove unnecessary return ret statement from .remove()
> - Move platform_set_drvdata() at the top of probe. 
> 
> v12:
> - Rebase to linux 5.9-rc4
> - Add Reviewed-by tags from Andy Shevchenko & Rob Herring.
> 
> v11:
> - Address below review concerns (Andy Shevchenko)
>   * Fix a issue with dev_err_probe() usage & improve the usage.
>   * Fix & improve a ordering issue with clk_enable/disable &
>     reset_control assert/deassert.
> 
> v10:
> - Removed unused of_device.h and added platform_device.h
>   & mod_devicetable.h
> 
> v9:
> - Address code quality related review concerns (Andy Shevchenko)
> - Use devm_add_action_or_reset() instead of explicit unwind calls.
> 
> v8:
> - Remove fan related optional properties usage, keep
>   them as default. If needed, change pwm-fan driver
>   separately in future to add them as generic properties.
> 
> v7:
> - Address code quality related review concerns.
> - Rename fan related property to pwm-*.
> - Fix one make dt_binding_check reported error.
> 
> v6:
> - Readjust .apply op as per review feedback.
> - Add back pwm-cells property to resolve make dt_binding_check error.
>   pwm-cells is a required property for PWM driver.
> - Add back fan related optional properties.
> 
> v5:
> - Address below review concerns from Uwe Kleine-K?nig.
>   * Improve comments about Limitations.
>   * Use return value of regmap_update_bits if container function returns
>     error code.
>   * Modify .apply op to have strict checking for fixed period supported
>     by PWM HW.
>   * Use u64 as type when use min_t for duty_cycle.
>   * Add reset_control_assert() in failure case in probe where it was missing
>     earlier.
> - Remove fan specific optional properties from pwm dt binding document (Rob Herring)
> 
> v4:
> - Address below review concerns from Uwe Kleine-K?nig.
>   * Improve notes and limitations comments.
>   * Add common prefixes for all #defines.
>   * Modify/Improve logic in .apply & .get_state ops as advised.
>   * Skip error messages in probe when error is -EPROBE_DEFER.
>   * Add dependencies in Kconfig (OF & HAS_IOMEM) and add select REGMAP_MMIO.
>   * Address other code quality related review concerns.
> - Fix make dt_binding_check reported error in YAML file.
> 
> v3:
> - Address below review concerns from Uwe Kleine-K?nig.
>   * Remove fan rpm calibration task from the driver.
>   * Modify apply op as per the review feedback.
>   * Add roundup & round down where necessary.
>   * Address other misc code quality related review concerns.
>   * Use devm_reset_control_get_exclusive(). (Philipp Zabel)
>   * Improve dt binding document.
> 
> v2:
> - Address below review concerns from Uwe Kleine-K?nig.
>   * Add notes and limitations about PWM HW.
>   * Rename all functions and structure to lgm_pwm_* 
>   * Readjust space aligninment in structure fields to single space.
>   * Switch to using apply instead of config/enable/disable.
>   * Address other code quality related concerns.
>   * Rebase to 5.8-rc1.
> - Address review concerns in dt binding YAML from Rob Herring.
> 
> v1:
> - Initial version.
> 
> 
> Rahul Tanwar (2):
>   Add DT bindings YAML schema for PWM fan controller of LGM SoC
>   Add PWM fan controller driver for LGM SoC
> 
>  .../devicetree/bindings/pwm/intel,lgm-pwm.yaml     |  44 ++++
>  drivers/pwm/Kconfig                                |  11 +
>  drivers/pwm/Makefile                               |   1 +
>  drivers/pwm/pwm-intel-lgm.c                        | 246 +++++++++++++++++++++
>  4 files changed, 302 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/pwm/intel,lgm-pwm.yaml
>  create mode 100644 drivers/pwm/pwm-intel-lgm.c

Applied, thanks.

Thierry

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