[PATCH v4 0/2] Add PWM support for Intel Keem Bay SoC

[PATCH v4 0/2] Add PWM support for Intel Keem Bay SoC

[vineetha.g.jaya.kumaran]

From: "Vineetha G. Jaya Kumaran" <vineetha.g.jaya.kumaran@intel.com>

Hi,

This patch set enables support for PWM on the Intel Keem Bay SoC.
Keem Bay is an ARM based SoC, and the GPIO module allows
configuration of 6 PWM outputs. Patch 1 adds the PWM driver and
Patch 2 is for the required Device Tree bindings documentation.

This driver was tested on the Keem Bay evaluation module board.

Thank you.

Best regards,
Vineetha

Changes since v3:
-Removed variable for address and calculate in place instead
-Utilized u32_replace_bits() when updating KMB_PWM_LEADIN_OFFSET
-Utilized dev_err_probe() for error reporting
-Updated comments to use physical units
-Updated error check for pwmchip_add()

Changes since v2:
-Include documentation about HW limitation/behaviour
-Use hex values for KMB_PWM_COUNT_MAX
-Redefine register macros
-Utilize FIELD_GET/FIELD_PREP for calculating pwm_l/h_count and pwm_count
-Round up duty cycle/period values
-Get current hardware state in .apply instead of cached values
-Do a polarity check before .enabled
-Round high time/low time to closest value
-Set enable bit in KMB_PWM_LEADIN_OFFSET to 0 in probe
-Correct the naming for MODULE_ALIAS
-Add additionalProperties: false in DT bindings

Changes since v1:
-Updated licensing info, "clocks" property and example in DT bindings
-Updated name of DT bindings document to match compatible string
-Removed 1 patch for addition of new sysfs attribute "count"
-Added support for COMPILE_TEST in Kconfig
-Updated naming of defines and regmap attribute
-Updated calculation of waveform high time and low time
-Added range checking for waveform high/low time
-Implemented .get_state
-Removed register writes for lead-in and count values (left to default)
-Updated register access to single-access
-Folded keembay_pwm_enable/disable_channel, keembay_pwm_config_period/duty_cycle,
 and keembay_pwm_config into keembay_pwm_apply
-Updated error messages/error codes
-Removed pwm_disable from keembay_pwm_remove
-Removed clk_prepare/clk_enable/clk_disable from driver

Lai, Poey Seng (1):
  pwm: Add PWM driver for Intel Keem Bay

Vineetha G. Jaya Kumaran (1):
  dt-bindings: pwm: keembay: Add bindings for Intel Keem Bay PWM

 .../devicetree/bindings/pwm/intel,keembay-pwm.yaml |  47 +++++
 drivers/pwm/Kconfig                                |   9 +
 drivers/pwm/Makefile                               |   1 +
 drivers/pwm/pwm-keembay.c                          | 229 +++++++++++++++++++++
 4 files changed, 286 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/pwm/intel,keembay-pwm.yaml
 create mode 100644 drivers/pwm/pwm-keembay.c

-- 
1.9.1

[PATCH v4 1/2] pwm: Add PWM driver for Intel Keem Bay

[vineetha.g.jaya.kumaran]

From: "Lai, Poey Seng" <poey.seng.lai@intel.com>

Enable PWM support for the Intel Keem Bay SoC.

Signed-off-by: Lai, Poey Seng <poey.seng.lai@intel.com>
Signed-off-by: Vineetha G. Jaya Kumaran <vineetha.g.jaya.kumaran@intel.com>
---
 drivers/pwm/Kconfig       |   9 ++
 drivers/pwm/Makefile      |   1 +
 drivers/pwm/pwm-keembay.c | 229 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 239 insertions(+)
 create mode 100644 drivers/pwm/pwm-keembay.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 7dbcf69..0a68a167 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -560,4 +560,13 @@ config PWM_ZX
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-zx.
 
+config PWM_KEEMBAY
+	tristate "Intel Keem Bay PWM driver"
+	depends on ARM64 || COMPILE_TEST
+	help
+	  The platform driver for Intel Keem Bay PWM controller.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-keembay.
+
 endif
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 2c2ba0a..293e48f 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -54,3 +54,4 @@ obj-$(CONFIG_PWM_TWL)		+= pwm-twl.o
 obj-$(CONFIG_PWM_TWL_LED)	+= pwm-twl-led.o
 obj-$(CONFIG_PWM_VT8500)	+= pwm-vt8500.o
 obj-$(CONFIG_PWM_ZX)		+= pwm-zx.o
+obj-$(CONFIG_PWM_KEEMBAY)	+= pwm-keembay.o
diff --git a/drivers/pwm/pwm-keembay.c b/drivers/pwm/pwm-keembay.c
new file mode 100644
index 00000000..18a74ac
--- /dev/null
+++ b/drivers/pwm/pwm-keembay.c
@@ -0,0 +1,229 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Intel Keem Bay PWM driver
+ *
+ * Copyright (C) 2020 Intel Corporation
+ * Authors: Lai Poey Seng <poey.seng.lai@intel.com>
+ *          Vineetha G. Jaya Kumaran <vineetha.g.jaya.kumaran@intel.com>
+ *
+ * Limitation:
+ * - Upon disabling a channel, the currently running
+ *   period will not be completed. However, upon
+ *   reconfiguration of the duty cycle/period, the
+ *   currently running period will be completed first.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/regmap.h>
+
+#define KMB_TOTAL_PWM_CHANNELS		6
+#define KMB_PWM_COUNT_MAX		0xffff
+#define KMB_PWM_EN_BIT			BIT(31)
+
+/* Mask */
+#define KMB_PWM_HIGH_MASK		GENMASK(31, 16)
+#define KMB_PWM_LOW_MASK		GENMASK(15, 0)
+#define KMB_PWM_COUNT_MASK		GENMASK(31, 0)
+
+/* PWM Register offset */
+#define KMB_PWM_LEADIN_OFFSET(ch)	(0x00 + 4 * (ch))
+#define KMB_PWM_HIGHLOW_OFFSET(ch)	(0x20 + 4 * (ch))
+
+struct keembay_pwm {
+	struct pwm_chip chip;
+	struct device *dev;
+	struct clk *clk;
+	void __iomem *base;
+};
+
+static inline struct keembay_pwm *to_keembay_pwm_dev(struct pwm_chip *chip)
+{
+	return container_of(chip, struct keembay_pwm, chip);
+}
+
+static inline void keembay_pwm_update_bits(struct keembay_pwm *priv, u32 mask,
+					   u32 val, u32 offset)
+{
+	u32 buff = readl(priv->base + offset);
+
+	buff = u32_replace_bits(buff, val, mask);
+	writel(buff, priv->base + offset);
+}
+
+static void keembay_pwm_enable(struct keembay_pwm *priv, int ch)
+{
+	keembay_pwm_update_bits(priv, KMB_PWM_EN_BIT, 1,
+				KMB_PWM_LEADIN_OFFSET(ch));
+}
+
+static void keembay_pwm_disable(struct keembay_pwm *priv, int ch)
+{
+	keembay_pwm_update_bits(priv, KMB_PWM_EN_BIT, 0,
+				KMB_PWM_LEADIN_OFFSET(ch));
+}
+
+static void keembay_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+				  struct pwm_state *state)
+{
+	struct keembay_pwm *priv = to_keembay_pwm_dev(chip);
+	unsigned long long pwm_h_count, pwm_l_count;
+	unsigned long clk_rate;
+	u32 buff;
+
+	clk_rate = clk_get_rate(priv->clk);
+
+	/* Read channel enabled status */
+	buff = readl(priv->base + KMB_PWM_LEADIN_OFFSET(pwm->hwpwm));
+	if (buff & KMB_PWM_EN_BIT)
+		state->enabled = true;
+	else
+		state->enabled = false;
+
+	/* Read period and duty cycle */
+	buff = readl(priv->base + KMB_PWM_HIGHLOW_OFFSET(pwm->hwpwm));
+	pwm_l_count = FIELD_GET(KMB_PWM_LOW_MASK, buff) * NSEC_PER_SEC;
+	pwm_h_count = FIELD_GET(KMB_PWM_HIGH_MASK, buff) * NSEC_PER_SEC;
+	state->duty_cycle = DIV_ROUND_UP_ULL(pwm_h_count, clk_rate);
+	state->period = DIV_ROUND_UP_ULL(pwm_h_count + pwm_l_count, clk_rate);
+}
+
+static int keembay_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			     const struct pwm_state *state)
+{
+	struct keembay_pwm *priv = to_keembay_pwm_dev(chip);
+	struct pwm_state current_state;
+	u16 pwm_h_count, pwm_l_count;
+	unsigned long long div;
+	unsigned long clk_rate;
+	u32 pwm_count = 0;
+
+	keembay_pwm_get_state(chip, pwm, &current_state);
+
+	if (state->polarity != PWM_POLARITY_NORMAL)
+		return -ENOSYS;
+
+	if (!state->enabled && current_state.enabled) {
+		keembay_pwm_disable(priv, pwm->hwpwm);
+		return 0;
+	}
+
+	/*
+	 * The upper 16 bits of the KMB_PWM_HIGHLOW_OFFSET register contain
+	 * the high time of the waveform, while the last 16 bits contain
+	 * the low time of the waveform, in terms of clock cycles.
+	 *
+	 * high time = clock rate * duty cycle / NSEC_PER_SEC
+	 * low time =  clock rate * (period - duty cycle) / NSEC_PER_SEC
+	 *
+	 * e.g. For period 50us, duty cycle 30us, and clock rate 500MHz:
+	 * high time = (500MHz * 30us) / 1000000000 = 0x3A98
+	 * low time = (500MHz * 20us) / 1000000000 = 0x2710
+	 * Value written to KMB_PWM_HIGHLOW_OFFSET = 0x3A982710
+	 */
+
+	clk_rate = clk_get_rate(priv->clk);
+
+	/* Configure waveform high time */
+	div = clk_rate * state->duty_cycle;
+	div = DIV_ROUND_CLOSEST_ULL(div, NSEC_PER_SEC);
+	if (div > KMB_PWM_COUNT_MAX)
+		return -ERANGE;
+
+	pwm_h_count = div;
+
+	/* Configure waveform low time */
+	div = clk_rate * (state->period - state->duty_cycle);
+	div = DIV_ROUND_CLOSEST_ULL(div, NSEC_PER_SEC);
+	if (div > KMB_PWM_COUNT_MAX)
+		return -ERANGE;
+
+	pwm_l_count = div;
+
+	pwm_count = FIELD_PREP(KMB_PWM_HIGH_MASK, pwm_h_count) |
+		    FIELD_PREP(KMB_PWM_LOW_MASK, pwm_l_count);
+
+	writel(pwm_count, priv->base + KMB_PWM_HIGHLOW_OFFSET(pwm->hwpwm));
+
+	if (state->enabled && !current_state.enabled)
+		keembay_pwm_enable(priv, pwm->hwpwm);
+
+	return 0;
+}
+
+static const struct pwm_ops keembay_pwm_ops = {
+	.owner = THIS_MODULE,
+	.apply = keembay_pwm_apply,
+	.get_state = keembay_pwm_get_state,
+};
+
+static int keembay_pwm_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct keembay_pwm *priv;
+	int ret, ch;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(priv->clk))
+		dev_err_probe(dev, PTR_ERR(priv->clk),
+			     "Failed to get clock\n");
+
+	priv->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	priv->chip.base = -1;
+	priv->chip.dev = dev;
+	priv->chip.ops = &keembay_pwm_ops;
+	priv->chip.npwm = KMB_TOTAL_PWM_CHANNELS;
+
+	ret = pwmchip_add(&priv->chip);
+	if (ret) {
+		dev_err(dev, "Failed to add PWM chip: %pe\n", ERR_PTR(ret));
+		return ret;
+	}
+
+	/* Ensure enable bit for each channel is cleared at boot */
+	for (ch = 0; ch < KMB_TOTAL_PWM_CHANNELS; ch++)
+		keembay_pwm_disable(priv, ch);
+
+	platform_set_drvdata(pdev, priv);
+
+	return 0;
+}
+
+static int keembay_pwm_remove(struct platform_device *pdev)
+{
+	struct keembay_pwm *priv = platform_get_drvdata(pdev);
+
+	return pwmchip_remove(&priv->chip);
+}
+
+static const struct of_device_id keembay_pwm_of_match[] = {
+	{ .compatible = "intel,keembay-pwm" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, keembay_pwm_of_match);
+
+static struct platform_driver keembay_pwm_driver = {
+	.probe	= keembay_pwm_probe,
+	.remove	= keembay_pwm_remove,
+	.driver	= {
+		.name = "pwm-keembay",
+		.of_match_table = keembay_pwm_of_match,
+	},
+};
+module_platform_driver(keembay_pwm_driver);
+
+MODULE_ALIAS("platform:pwm-keembay");
+MODULE_DESCRIPTION("Intel Keem Bay PWM driver");
+MODULE_LICENSE("GPL v2");
-- 
1.9.1

Re: [PATCH v4 1/2] pwm: Add PWM driver for Intel Keem Bay

[Andy Shevchenko]

On Sat, Aug 22, 2020 at 10:30:45PM +0800, vineetha.g.jaya.kumaran@intel.com wrote:
> From: "Lai, Poey Seng" <poey.seng.lai@intel.com>
> 

Side note, please use my @linux.intel.com address in the Cc list.

> Enable PWM support for the Intel Keem Bay SoC.

...

> + * Authors: Lai Poey Seng <poey.seng.lai@intel.com>
> + *          Vineetha G. Jaya Kumaran <vineetha.g.jaya.kumaran@intel.com>

Seems you missed Co-developed-by in the tag block of commit message.

...

> +#include <linux/bitfield.h>
> +#include <linux/clk.h>
> +#include <linux/io.h>
> +#include <linux/module.h>

> +#include <linux/of.h>

There is no user of this header. But mod_devicetable.h is missing.

> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +#include <linux/regmap.h>

...

> +	/*
> +	 * The upper 16 bits of the KMB_PWM_HIGHLOW_OFFSET register contain
> +	 * the high time of the waveform, while the last 16 bits contain
> +	 * the low time of the waveform, in terms of clock cycles.
> +	 *
> +	 * high time = clock rate * duty cycle / NSEC_PER_SEC
> +	 * low time =  clock rate * (period - duty cycle) / NSEC_PER_SEC
> +	 *
> +	 * e.g. For period 50us, duty cycle 30us, and clock rate 500MHz:

> +	 * high time = (500MHz * 30us) / 1000000000 = 0x3A98

10^9 divisor now is redundant. It's school physics about units.

> +	 * low time = (500MHz * 20us) / 1000000000 = 0x2710

Ditto.

> +	 * Value written to KMB_PWM_HIGHLOW_OFFSET = 0x3A982710
> +	 */

Note, in the code you are operating different units.

...

> +	div = clk_rate * state->duty_cycle;
> +	div = DIV_ROUND_CLOSEST_ULL(div, NSEC_PER_SEC);

For example, here you have clock rate in Hz, duty cycle in ns, that's why you
need to use NSEC_PER_SEC divisor here.

...

> +	div = clk_rate * (state->period - state->duty_cycle);
> +	div = DIV_ROUND_CLOSEST_ULL(div, NSEC_PER_SEC);

Same here.

(Just to be clear, code is okay!)

...

> +	priv->clk = devm_clk_get(&pdev->dev, NULL);
> +	if (IS_ERR(priv->clk))
> +		dev_err_probe(dev, PTR_ERR(priv->clk),
> +			     "Failed to get clock\n");

First of all, it can be one line, second, it misses something...

-- 
With Best Regards,
Andy Shevchenko

RE: [PATCH v4 1/2] pwm: Add PWM driver for Intel Keem Bay

[G Jaya Kumaran, Vineetha]

> -----Original Message-----
> From: linux-pwm-owner@vger.kernel.org <linux-pwm-
> owner@vger.kernel.org> On Behalf Of Andy Shevchenko
> Sent: Monday, August 24, 2020 3:53 PM
> To: G Jaya Kumaran, Vineetha <vineetha.g.jaya.kumaran@intel.com>
> Cc: thierry.reding@gmail.com; u.kleine-koenig@pengutronix.de;
> robh+dt@kernel.org; linux-pwm@vger.kernel.org;
> devicetree@vger.kernel.org; Wan Mohamad, Wan Ahmad Zainie
> <wan.ahmad.zainie.wan.mohamad@intel.com>; Raja Subramanian, Lakshmi
> Bai <lakshmi.bai.raja.subramanian@intel.com>
> Subject: Re: [PATCH v4 1/2] pwm: Add PWM driver for Intel Keem Bay
> 
> On Sat, Aug 22, 2020 at 10:30:45PM +0800,
> vineetha.g.jaya.kumaran@intel.com wrote:
> > From: "Lai, Poey Seng" <poey.seng.lai@intel.com>
> >
> 
> Side note, please use my @linux.intel.com address in the Cc list.
> 
> > Enable PWM support for the Intel Keem Bay SoC.
> 
> ...
> 
> > + * Authors: Lai Poey Seng <poey.seng.lai@intel.com>
> > + *          Vineetha G. Jaya Kumaran <vineetha.g.jaya.kumaran@intel.com>
> 
> Seems you missed Co-developed-by in the tag block of commit message.
> 

OK, I will add this in.

> ...
> 
> > +#include <linux/bitfield.h>
> > +#include <linux/clk.h>
> > +#include <linux/io.h>
> > +#include <linux/module.h>
> 
> > +#include <linux/of.h>
> 
> There is no user of this header. But mod_devicetable.h is missing.
> 

OK, will remove this, and add in mod_devicetable.h

> > +#include <linux/platform_device.h>
> > +#include <linux/pwm.h>
> > +#include <linux/regmap.h>
> 
> ...
> 
> > +	/*
> > +	 * The upper 16 bits of the KMB_PWM_HIGHLOW_OFFSET register
> contain
> > +	 * the high time of the waveform, while the last 16 bits contain
> > +	 * the low time of the waveform, in terms of clock cycles.
> > +	 *
> > +	 * high time = clock rate * duty cycle / NSEC_PER_SEC
> > +	 * low time =  clock rate * (period - duty cycle) / NSEC_PER_SEC
> > +	 *
> > +	 * e.g. For period 50us, duty cycle 30us, and clock rate 500MHz:
> 
> > +	 * high time = (500MHz * 30us) / 1000000000 = 0x3A98
> 
> 10^9 divisor now is redundant. It's school physics about units.
> 
> > +	 * low time = (500MHz * 20us) / 1000000000 = 0x2710
> 
> Ditto.
> 

Thank you for pointing this out - will fix this.

> > +	 * Value written to KMB_PWM_HIGHLOW_OFFSET = 0x3A982710
> > +	 */
> 
> Note, in the code you are operating different units.
> 
> ...
> 
> > +	div = clk_rate * state->duty_cycle;
> > +	div = DIV_ROUND_CLOSEST_ULL(div, NSEC_PER_SEC);
> 
> For example, here you have clock rate in Hz, duty cycle in ns, that's why you
> need to use NSEC_PER_SEC divisor here.
> 
> ...
> 
> > +	div = clk_rate * (state->period - state->duty_cycle);
> > +	div = DIV_ROUND_CLOSEST_ULL(div, NSEC_PER_SEC);
> 
> Same here.
> 
> (Just to be clear, code is okay!)
> 
> ...
> 
> > +	priv->clk = devm_clk_get(&pdev->dev, NULL);
> > +	if (IS_ERR(priv->clk))
> > +		dev_err_probe(dev, PTR_ERR(priv->clk),
> > +			     "Failed to get clock\n");
> 
> First of all, it can be one line, second, it misses something...
> 

Missed the return - sorry, will fix it.

Thanks for the feedback, Andy. Will make the changes and resubmit.

> --
> With Best Regards,
> Andy Shevchenko
> 

[PATCH v4 2/2] dt-bindings: pwm: keembay: Add bindings for Intel Keem Bay PWM

[vineetha.g.jaya.kumaran]

From: "Vineetha G. Jaya Kumaran" <vineetha.g.jaya.kumaran@intel.com>

Add PWM Device Tree bindings documentation for the Intel Keem Bay SoC.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Vineetha G. Jaya Kumaran <vineetha.g.jaya.kumaran@intel.com>
---
 .../devicetree/bindings/pwm/intel,keembay-pwm.yaml | 47 ++++++++++++++++++++++
 1 file changed, 47 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/pwm/intel,keembay-pwm.yaml

diff --git a/Documentation/devicetree/bindings/pwm/intel,keembay-pwm.yaml b/Documentation/devicetree/bindings/pwm/intel,keembay-pwm.yaml
new file mode 100644
index 00000000..a374334
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/intel,keembay-pwm.yaml
@@ -0,0 +1,47 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright (C) 2020 Intel Corporation
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pwm/intel,keembay-pwm.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Intel Keem Bay PWM Device Tree Bindings
+
+maintainers:
+  - Vineetha G. Jaya Kumaran <vineetha.g.jaya.kumaran@intel.com>
+
+allOf:
+  - $ref: pwm.yaml#
+
+properties:
+  compatible:
+    enum:
+      - intel,keembay-pwm
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  "#pwm-cells":
+    const: 2
+
+required:
+ - compatible
+ - reg
+ - clocks
+ - '#pwm-cells'
+
+additionalProperties: false
+
+examples:
+  - |
+    #define KEEM_BAY_A53_GPIO
+
+    pwm@203200a0 {
+      compatible = "intel,keembay-pwm";
+      reg = <0x203200a0 0xe8>;
+      clocks = <&scmi_clk KEEM_BAY_A53_GPIO>;
+      #pwm-cells = <2>;
+    };
-- 
1.9.1