[PATCH v6 0/5] PWM and keyboard backlight driver for ARM Macs

[PATCH v6 0/5] PWM and keyboard backlight driver for ARM Macs

[Sasha Finkelstein]

Hi,

This is the v6 of the patch series to add PWM and keyboard backlight
driver for ARM macs. This time the changes are a bit more substantial
and include the changes to the t600x (M1 Pro/Max) device trees.

Here is hoping that this time, the paint on this shed is up
to everyone's standards.

Changes in v1:
Addressing the review comments.

Changes in v2:
Added the reviewed-by and acked-by tags.
Addressing a review comment.

Changes in v3 and v4:
Addressing the review comments.

Changes in v5:
Added t600x device tree changes

v1: https://www.spinics.net/lists/linux-pwm/msg19500.html
v2: https://www.spinics.net/lists/linux-pwm/msg19562.html
v3: https://www.spinics.net/lists/linux-pwm/msg19901.html
v4: https://www.spinics.net/lists/linux-pwm/msg20093.html
v5: https://www.spinics.net/lists/linux-pwm/msg20150.html

Sasha Finkelstein (5):
  dt-bindings: pwm: Add Apple PWM controller
  pwm: Add Apple PWM controller
  arm64: dts: apple: t8103: Add PWM controller
  arm64: dts: apple: t600x: Add PWM controller
  MAINTAINERS: Add entries for Apple PWM driver

 .../bindings/pwm/apple,s5l-fpwm.yaml          |  51 ++++++
 MAINTAINERS                                   |   2 +
 arch/arm64/boot/dts/apple/t600x-die0.dtsi     |   9 +
 .../arm64/boot/dts/apple/t600x-j314-j316.dtsi |  18 ++
 arch/arm64/boot/dts/apple/t8103-j293.dts      |  17 ++
 arch/arm64/boot/dts/apple/t8103-j313.dts      |  17 ++
 arch/arm64/boot/dts/apple/t8103.dtsi          |   9 +
 drivers/pwm/Kconfig                           |  12 ++
 drivers/pwm/Makefile                          |   1 +
 drivers/pwm/pwm-apple.c                       | 156 ++++++++++++++++++
 10 files changed, 292 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/pwm/apple,s5l-fpwm.yaml
 create mode 100644 drivers/pwm/pwm-apple.c

-- 
2.37.1 (Apple Git-137.1)

[PATCH v6 1/5] dt-bindings: pwm: Add Apple PWM controller

[Sasha Finkelstein]

Apple SoCs such as the M1 contain a PWM controller used
among other things to control the keyboard backlight.

Signed-off-by: Sasha Finkelstein <fnkl.kernel@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Sven Peter <sven@svenpeter.dev>
---
 .../bindings/pwm/apple,s5l-fpwm.yaml          | 51 +++++++++++++++++++
 1 file changed, 51 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/pwm/apple,s5l-fpwm.yaml

diff --git a/Documentation/devicetree/bindings/pwm/apple,s5l-fpwm.yaml b/Documentation/devicetree/bindings/pwm/apple,s5l-fpwm.yaml
new file mode 100644
index 000000000000..142157bff0cd
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/apple,s5l-fpwm.yaml
@@ -0,0 +1,51 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pwm/apple,s5l-fpwm.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Apple FPWM controller
+
+maintainers:
+  - asahi@lists.linux.dev
+  - Sasha Finkelstein <fnkl.kernel@gmail.com>
+
+description: PWM controller used for keyboard backlight on ARM Macs
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - apple,t8103-fpwm
+          - apple,t6000-fpwm
+          - apple,t8112-fpwm
+      - const: apple,s5l-fpwm
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  power-domains:
+    maxItems: 1
+
+  "#pwm-cells":
+    const: 2
+
+required:
+  - compatible
+  - reg
+  - clocks
+
+additionalProperties: false
+
+examples:
+  - |
+    pwm@235044000 {
+      compatible = "apple,t8103-fpwm", "apple,s5l-fpwm";
+      reg = <0x35044000 0x4000>;
+      power-domains = <&ps_fpwm1>;
+      clocks = <&clkref>;
+      #pwm-cells = <2>;
+    };
-- 
2.37.1 (Apple Git-137.1)

[PATCH v6 2/5] pwm: Add Apple PWM controller

[Sasha Finkelstein]

Adds the Apple PWM controller driver.

Signed-off-by: Sasha Finkelstein <fnkl.kernel@gmail.com>
Acked-by: Sven Peter <sven@svenpeter.dev>
---
 drivers/pwm/Kconfig     |  12 ++++
 drivers/pwm/Makefile    |   1 +
 drivers/pwm/pwm-apple.c | 156 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 169 insertions(+)
 create mode 100644 drivers/pwm/pwm-apple.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index dae023d783a2..8df861b1f4a3 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -51,6 +51,18 @@ config PWM_AB8500
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-ab8500.
 
+config PWM_APPLE
+	tristate "Apple SoC PWM support"
+	depends on ARCH_APPLE || COMPILE_TEST
+	help
+	  Generic PWM framework driver for PWM controller present on
+	  Apple SoCs
+
+	  Say Y here if you have an ARM Apple laptop, otherwise say N
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-apple.
+
 config PWM_ATMEL
 	tristate "Atmel PWM support"
 	depends on ARCH_AT91 || COMPILE_TEST
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 7bf1a29f02b8..19899b912e00 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -2,6 +2,7 @@
 obj-$(CONFIG_PWM)		+= core.o
 obj-$(CONFIG_PWM_SYSFS)		+= sysfs.o
 obj-$(CONFIG_PWM_AB8500)	+= pwm-ab8500.o
+obj-$(CONFIG_PWM_APPLE)		+= pwm-apple.o
 obj-$(CONFIG_PWM_ATMEL)		+= pwm-atmel.o
 obj-$(CONFIG_PWM_ATMEL_HLCDC_PWM)	+= pwm-atmel-hlcdc.o
 obj-$(CONFIG_PWM_ATMEL_TCB)	+= pwm-atmel-tcb.o
diff --git a/drivers/pwm/pwm-apple.c b/drivers/pwm/pwm-apple.c
new file mode 100644
index 000000000000..5360583a5fa6
--- /dev/null
+++ b/drivers/pwm/pwm-apple.c
@@ -0,0 +1,156 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+/*
+ * Driver for the Apple SoC PWM controller
+ *
+ * Copyright The Asahi Linux Contributors
+ *
+ * Limitations:
+ * - The writes to cycle registers are shadowed until a write to
+ *   the control register.
+ * - If both OFF_CYCLES and ON_CYCLES are set to 0, the output
+ *   is a constant off signal.
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/io.h>
+#include <linux/clk.h>
+#include <linux/math64.h>
+
+#define APPLE_PWM_CTRL        0x00
+#define APPLE_PWM_ON_CYCLES   0x1c
+#define APPLE_PWM_OFF_CYCLES  0x18
+
+#define APPLE_CTRL_ENABLE        BIT(0)
+#define APPLE_CTRL_MODE          BIT(2)
+#define APPLE_CTRL_UPDATE        BIT(5)
+#define APPLE_CTRL_TRIGGER       BIT(9)
+#define APPLE_CTRL_INVERT        BIT(10)
+#define APPLE_CTRL_OUTPUT_ENABLE BIT(14)
+
+struct apple_pwm {
+	struct pwm_chip chip;
+	void __iomem *base;
+	u64 clkrate;
+};
+
+static inline struct apple_pwm *to_apple_pwm(struct pwm_chip *chip)
+{
+	return container_of(chip, struct apple_pwm, chip);
+}
+
+static int apple_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			   const struct pwm_state *state)
+{
+	struct apple_pwm *fpwm;
+
+	if (state->polarity == PWM_POLARITY_INVERSED)
+		return -EINVAL;
+
+	fpwm = to_apple_pwm(chip);
+	if (state->enabled) {
+		u64 on_cycles, off_cycles;
+
+		on_cycles = mul_u64_u64_div_u64(fpwm->clkrate,
+						state->duty_cycle, NSEC_PER_SEC);
+		if (on_cycles > 0xFFFFFFFF)
+			return -ERANGE;
+
+		off_cycles = mul_u64_u64_div_u64(fpwm->clkrate,
+						 state->period, NSEC_PER_SEC) - on_cycles;
+		if (off_cycles > 0xFFFFFFFF)
+			return -ERANGE;
+
+		writel(on_cycles, fpwm->base + APPLE_PWM_ON_CYCLES);
+		writel(off_cycles, fpwm->base + APPLE_PWM_OFF_CYCLES);
+		writel(APPLE_CTRL_ENABLE | APPLE_CTRL_OUTPUT_ENABLE | APPLE_CTRL_UPDATE,
+		       fpwm->base + APPLE_PWM_CTRL);
+	} else {
+		writel(0, fpwm->base + APPLE_PWM_CTRL);
+	}
+	return 0;
+}
+
+static int apple_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+			   struct pwm_state *state)
+{
+	struct apple_pwm *fpwm;
+	u32 on_cycles, off_cycles, ctrl;
+
+	fpwm = to_apple_pwm(chip);
+
+	ctrl = readl(fpwm->base + APPLE_PWM_CTRL);
+	on_cycles = readl(fpwm->base + APPLE_PWM_ON_CYCLES);
+	off_cycles = readl(fpwm->base + APPLE_PWM_OFF_CYCLES);
+
+	state->enabled = (ctrl & APPLE_CTRL_ENABLE) && (ctrl & APPLE_CTRL_OUTPUT_ENABLE);
+	state->polarity = PWM_POLARITY_NORMAL;
+	// on_cycles + off_cycles is 33 bits, NSEC_PER_SEC is 30, there is no overflow
+	state->duty_cycle = DIV64_U64_ROUND_UP((u64)on_cycles * NSEC_PER_SEC, fpwm->clkrate);
+	state->period = DIV64_U64_ROUND_UP(((u64)off_cycles + (u64)on_cycles) *
+					    NSEC_PER_SEC, fpwm->clkrate);
+
+	return 0;
+}
+
+static const struct pwm_ops apple_pwm_ops = {
+	.apply = apple_pwm_apply,
+	.get_state = apple_pwm_get_state,
+	.owner = THIS_MODULE,
+};
+
+static int apple_pwm_probe(struct platform_device *pdev)
+{
+	struct apple_pwm *fpwm;
+	struct clk *clk;
+	int ret;
+
+	fpwm = devm_kzalloc(&pdev->dev, sizeof(*fpwm), GFP_KERNEL);
+	if (!fpwm)
+		return -ENOMEM;
+
+	fpwm->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(fpwm->base))
+		return dev_err_probe(&pdev->dev, PTR_ERR(fpwm->base), "unable to map mmio");
+
+	clk = devm_clk_get_enabled(&pdev->dev, NULL);
+	if (IS_ERR(clk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(clk), "unable to get the clock");
+
+	/*
+	 * uses the 24MHz system clock on all existing devices, can only
+	 * happen if the device tree is broken
+	 */
+	fpwm->clkrate = clk_get_rate(clk);
+	if (fpwm->clkrate > NSEC_PER_SEC)
+		return dev_err_probe(&pdev->dev, -EINVAL, "pwm clock out of range");
+
+	fpwm->chip.dev = &pdev->dev;
+	fpwm->chip.npwm = 1;
+	fpwm->chip.ops = &apple_pwm_ops;
+
+	ret = devm_pwmchip_add(&pdev->dev, &fpwm->chip);
+	if (ret < 0)
+		return dev_err_probe(&pdev->dev, ret, "unable to add pwm chip");
+
+	return 0;
+}
+
+static const struct of_device_id apple_pwm_of_match[] = {
+	{ .compatible = "apple,s5l-fpwm" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, apple_pwm_of_match);
+
+static struct platform_driver apple_pwm_driver = {
+	.probe = apple_pwm_probe,
+	.driver = {
+		.name = "apple-pwm",
+		.of_match_table = apple_pwm_of_match,
+	},
+};
+module_platform_driver(apple_pwm_driver);
+
+MODULE_DESCRIPTION("Apple SoC PWM driver");
+MODULE_LICENSE("Dual MIT/GPL");
-- 
2.37.1 (Apple Git-137.1)

[PATCH v6 3/5] arm64: dts: apple: t8103: Add PWM controller

[Sasha Finkelstein]

Adds PWM controller and keyboard backlight bindings for M1 MacBooks

Signed-off-by: Sasha Finkelstein <fnkl.kernel@gmail.com>
Acked-by: Sven Peter <sven@svenpeter.dev>
---
 arch/arm64/boot/dts/apple/t8103-j293.dts | 17 +++++++++++++++++
 arch/arm64/boot/dts/apple/t8103-j313.dts | 17 +++++++++++++++++
 arch/arm64/boot/dts/apple/t8103.dtsi     |  9 +++++++++
 3 files changed, 43 insertions(+)

diff --git a/arch/arm64/boot/dts/apple/t8103-j293.dts b/arch/arm64/boot/dts/apple/t8103-j293.dts
index 151074109a11..7381dccc1613 100644
--- a/arch/arm64/boot/dts/apple/t8103-j293.dts
+++ b/arch/arm64/boot/dts/apple/t8103-j293.dts
@@ -11,10 +11,23 @@
 
 #include "t8103.dtsi"
 #include "t8103-jxxx.dtsi"
+#include <dt-bindings/leds/common.h>
 
 / {
 	compatible = "apple,j293", "apple,t8103", "apple,arm-platform";
 	model = "Apple MacBook Pro (13-inch, M1, 2020)";
+
+	led-controller {
+		compatible = "pwm-leds";
+		led-0 {
+			pwms = <&fpwm1 0 40000>;
+			label = "kbd_backlight";
+			function = LED_FUNCTION_KBD_BACKLIGHT;
+			color = <LED_COLOR_ID_WHITE>;
+			max-brightness = <255>;
+			default-state = "keep";
+		};
+	};
 };
 
 &bluetooth0 {
@@ -47,3 +60,7 @@ &i2c2 {
 &i2c4 {
 	status = "okay";
 };
+
+&fpwm1 {
+	status = "okay";
+};
\ No newline at end of file
diff --git a/arch/arm64/boot/dts/apple/t8103-j313.dts b/arch/arm64/boot/dts/apple/t8103-j313.dts
index bc1f865aa790..1e26aa1ef525 100644
--- a/arch/arm64/boot/dts/apple/t8103-j313.dts
+++ b/arch/arm64/boot/dts/apple/t8103-j313.dts
@@ -11,10 +11,23 @@
 
 #include "t8103.dtsi"
 #include "t8103-jxxx.dtsi"
+#include <dt-bindings/leds/common.h>
 
 / {
 	compatible = "apple,j313", "apple,t8103", "apple,arm-platform";
 	model = "Apple MacBook Air (M1, 2020)";
+
+	led-controller {
+		compatible = "pwm-leds";
+		led-0 {
+			pwms = <&fpwm1 0 40000>;
+			label = "kbd_backlight";
+			function = LED_FUNCTION_KBD_BACKLIGHT;
+			color = <LED_COLOR_ID_WHITE>;
+			max-brightness = <255>;
+			default-state = "keep";
+		};
+	};
 };
 
 &bluetooth0 {
@@ -39,3 +52,7 @@ &pcie0_dart_2 {
 
 /delete-node/ &port01;
 /delete-node/ &port02;
+
+&fpwm1 {
+	status = "okay";
+};
diff --git a/arch/arm64/boot/dts/apple/t8103.dtsi b/arch/arm64/boot/dts/apple/t8103.dtsi
index 9859219699f4..5300fd115561 100644
--- a/arch/arm64/boot/dts/apple/t8103.dtsi
+++ b/arch/arm64/boot/dts/apple/t8103.dtsi
@@ -432,6 +432,15 @@ i2c4: i2c@235020000 {
 			status = "disabled"; /* only used in J293 */
 		};
 
+		fpwm1: pwm@235044000 {
+			compatible = "apple,t8103-fpwm", "apple,s5l-fpwm";
+			reg = <0x2 0x35044000 0x0 0x4000>;
+			power-domains = <&ps_fpwm1>;
+			clocks = <&clkref>;
+			#pwm-cells = <2>;
+			status = "disabled";
+		};
+
 		serial0: serial@235200000 {
 			compatible = "apple,s5l-uart";
 			reg = <0x2 0x35200000 0x0 0x1000>;
-- 
2.37.1 (Apple Git-137.1)

[PATCH v6 4/5] arm64: dts: apple: t600x: Add PWM controller

[Sasha Finkelstein]

Adds PWM controller and keyboard backlight bindings for M1 Pro/Max MacBook Pros

Signed-off-by: Sasha Finkelstein <fnkl.kernel@gmail.com>
---
 arch/arm64/boot/dts/apple/t600x-die0.dtsi      |  9 +++++++++
 arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi | 18 ++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/arch/arm64/boot/dts/apple/t600x-die0.dtsi b/arch/arm64/boot/dts/apple/t600x-die0.dtsi
index 1c41954e3899..7065045dc43a 100644
--- a/arch/arm64/boot/dts/apple/t600x-die0.dtsi
+++ b/arch/arm64/boot/dts/apple/t600x-die0.dtsi
@@ -154,6 +154,15 @@ i2c5: i2c@39b054000 {
 		status = "disabled";
 	};
 
+	fpwm0: pwm@39b030000 {
+		compatible = "apple,t6000-fpwm", "apple,s5l-fpwm";
+		reg = <0x3 0x9b030000 0x0 0x4000>;
+		power-domains = <&ps_fpwm0>;
+		clocks = <&clkref>;
+		#pwm-cells = <2>;
+		status = "disabled";
+	};
+
 	serial0: serial@39b200000 {
 		compatible = "apple,s5l-uart";
 		reg = <0x3 0x9b200000 0x0 0x1000>;
diff --git a/arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi b/arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi
index 34906d522f0a..96de7165df6d 100644
--- a/arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi
+++ b/arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi
@@ -9,6 +9,8 @@
  * Copyright The Asahi Linux Contributors
  */
 
+#include <dt-bindings/leds/common.h>
+
 / {
 	aliases {
 		serial0 = &serial0;
@@ -34,6 +36,18 @@ memory@10000000000 {
 		device_type = "memory";
 		reg = <0x100 0 0x2 0>; /* To be filled by loader */
 	};
+
+	led-controller {
+		compatible = "pwm-leds";
+		led-0 {
+			pwms = <&fpwm0 0 40000>;
+			label = "kbd_backlight";
+			function = LED_FUNCTION_KBD_BACKLIGHT;
+			color = <LED_COLOR_ID_WHITE>;
+			max-brightness = <255>;
+			default-state = "keep";
+		};
+	};
 };
 
 &serial0 {
@@ -110,5 +124,9 @@ &pcie0_dart_3 {
 	status = "disabled";
 };
 
+&fpwm0 {
+	status = "okay";
+};
+
 /delete-node/ &port02;
 /delete-node/ &port03;
-- 
2.37.1 (Apple Git-137.1)

[PATCH v6 5/5] MAINTAINERS: Add entries for Apple PWM driver

[Sasha Finkelstein]

Add the MAINTAINERS entries for the driver

Signed-off-by: Sasha Finkelstein <fnkl.kernel@gmail.com>
Acked-by: Sven Peter <sven@svenpeter.dev>
---
 MAINTAINERS | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 7f86d02cb427..75bda5ab704d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1970,6 +1970,7 @@ F:	Documentation/devicetree/bindings/nvmem/apple,efuses.yaml
 F:	Documentation/devicetree/bindings/pci/apple,pcie.yaml
 F:	Documentation/devicetree/bindings/pinctrl/apple,pinctrl.yaml
 F:	Documentation/devicetree/bindings/power/apple*
+F:	Documentation/devicetree/bindings/pwm/pwm-apple.yaml
 F:	Documentation/devicetree/bindings/watchdog/apple,wdt.yaml
 F:	arch/arm64/boot/dts/apple/
 F:	drivers/bluetooth/hci_bcm4377.c
@@ -1985,6 +1986,7 @@ F:	drivers/mailbox/apple-mailbox.c
 F:	drivers/nvme/host/apple.c
 F:	drivers/nvmem/apple-efuses.c
 F:	drivers/pinctrl/pinctrl-apple-gpio.c
+F:	drivers/pwm/pwm-apple.c
 F:	drivers/soc/apple/*
 F:	drivers/watchdog/apple_wdt.c
 F:	include/dt-bindings/interrupt-controller/apple-aic.h
-- 
2.37.1 (Apple Git-137.1)

Re: [PATCH v6 4/5] arm64: dts: apple: t600x: Add PWM controller

[Hector Martin]

On 06/01/2023 22.58, Sasha Finkelstein wrote:
> Adds PWM controller and keyboard backlight bindings for M1 Pro/Max MacBook Pros
> 
> Signed-off-by: Sasha Finkelstein <fnkl.kernel@gmail.com>
> ---
>  arch/arm64/boot/dts/apple/t600x-die0.dtsi      |  9 +++++++++
>  arch/arm64/boot/dts/apple/t600x-j314-j316.dtsi | 18 ++++++++++++++++++
>  2 files changed, 27 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/apple/t600x-die0.dtsi b/arch/arm64/boot/dts/apple/t600x-die0.dtsi
> index 1c41954e3899..7065045dc43a 100644
> --- a/arch/arm64/boot/dts/apple/t600x-die0.dtsi
> +++ b/arch/arm64/boot/dts/apple/t600x-die0.dtsi
> @@ -154,6 +154,15 @@ i2c5: i2c@39b054000 {
>  		status = "disabled";
>  	};
>  
> +	fpwm0: pwm@39b030000 {
> +		compatible = "apple,t6000-fpwm", "apple,s5l-fpwm";
> +		reg = <0x3 0x9b030000 0x0 0x4000>;
> +		power-domains = <&ps_fpwm0>;
> +		clocks = <&clkref>;
> +		#pwm-cells = <2>;
> +		status = "disabled";
> +	};
> +

We usually keep device nodes sorted by address, so this is out of order
and should come before i2c (at least). No need to respin just for this
though, I can fix it when I apply it, so:

Acked-by: Hector Martin <marcan@marcan.st>

Maintainers: as we usually ask, please merge only the driver commit (#2)
via the PWM tree, we'll take care of DTs/MAINTAINERS/bindings via
asahi-soc so we can avoid serializing/blocking other DT changes.

- Hector

Re: [PATCH v6 2/5] pwm: Add Apple PWM controller

[Uwe Kleine-König]

[-- Attachment #1: Type: text/plain, Size: 5140 bytes --]

Hello Sasha,

On Fri, Jan 06, 2023 at 04:58:39PM +0300, Sasha Finkelstein wrote:
> Adds the Apple PWM controller driver.
> 
> Signed-off-by: Sasha Finkelstein <fnkl.kernel@gmail.com>
> Acked-by: Sven Peter <sven@svenpeter.dev>
> ---
>  drivers/pwm/Kconfig     |  12 ++++
>  drivers/pwm/Makefile    |   1 +
>  drivers/pwm/pwm-apple.c | 156 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 169 insertions(+)
>  create mode 100644 drivers/pwm/pwm-apple.c
> 
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index dae023d783a2..8df861b1f4a3 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -51,6 +51,18 @@ config PWM_AB8500
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called pwm-ab8500.
>  
> +config PWM_APPLE
> +	tristate "Apple SoC PWM support"
> +	depends on ARCH_APPLE || COMPILE_TEST
> +	help
> +	  Generic PWM framework driver for PWM controller present on
> +	  Apple SoCs
> +
> +	  Say Y here if you have an ARM Apple laptop, otherwise say N
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called pwm-apple.
> +
>  config PWM_ATMEL
>  	tristate "Atmel PWM support"
>  	depends on ARCH_AT91 || COMPILE_TEST
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index 7bf1a29f02b8..19899b912e00 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -2,6 +2,7 @@
>  obj-$(CONFIG_PWM)		+= core.o
>  obj-$(CONFIG_PWM_SYSFS)		+= sysfs.o
>  obj-$(CONFIG_PWM_AB8500)	+= pwm-ab8500.o
> +obj-$(CONFIG_PWM_APPLE)		+= pwm-apple.o
>  obj-$(CONFIG_PWM_ATMEL)		+= pwm-atmel.o
>  obj-$(CONFIG_PWM_ATMEL_HLCDC_PWM)	+= pwm-atmel-hlcdc.o
>  obj-$(CONFIG_PWM_ATMEL_TCB)	+= pwm-atmel-tcb.o
> diff --git a/drivers/pwm/pwm-apple.c b/drivers/pwm/pwm-apple.c
> new file mode 100644
> index 000000000000..5360583a5fa6
> --- /dev/null
> +++ b/drivers/pwm/pwm-apple.c
> @@ -0,0 +1,156 @@
> +// SPDX-License-Identifier: GPL-2.0 OR MIT
> +/*
> + * Driver for the Apple SoC PWM controller
> + *
> + * Copyright The Asahi Linux Contributors
> + *
> + * Limitations:
> + * - The writes to cycle registers are shadowed until a write to
> + *   the control register.
> + * - If both OFF_CYCLES and ON_CYCLES are set to 0, the output
> + *   is a constant off signal.

How does the PWM behave with *APPLE_PWM_CTRLAPPLE_PWM_CTRL = 0?
(typically: drives constant low)

> + */
> +
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +#include <linux/io.h>
> +#include <linux/clk.h>
> +#include <linux/math64.h>
> +
> +#define APPLE_PWM_CTRL        0x00
> +#define APPLE_PWM_ON_CYCLES   0x1c
> +#define APPLE_PWM_OFF_CYCLES  0x18
> +
> +#define APPLE_CTRL_ENABLE        BIT(0)
> +#define APPLE_CTRL_MODE          BIT(2)
> +#define APPLE_CTRL_UPDATE        BIT(5)
> +#define APPLE_CTRL_TRIGGER       BIT(9)
> +#define APPLE_CTRL_INVERT        BIT(10)
> +#define APPLE_CTRL_OUTPUT_ENABLE BIT(14)

In reply to v4 I wrote:

| Would be nice if the register prefix would match the register name. That
| is please either rename APPLE_PWM_CONTROL to APPLE_PWM_CTRL or use
| APPLE_PWM_CONTROL as prefix for the bit fields in that register.

well, one of the two options was bogus because it doesn't result in the
intended effect. You picked that broken option :-\
Can you please rename such that the (maybe new) name for APPLE_PWM_CTRL
is a prefix for the (maybe new) APPLE_CTRL_ENABLE and the other register
bit definitions?

> [...]
> +static int apple_pwm_probe(struct platform_device *pdev)
> +{
> +	struct apple_pwm *fpwm;
> +	struct clk *clk;
> +	int ret;
> +
> +	fpwm = devm_kzalloc(&pdev->dev, sizeof(*fpwm), GFP_KERNEL);
> +	if (!fpwm)
> +		return -ENOMEM;
> +
> +	fpwm->base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(fpwm->base))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(fpwm->base), "unable to map mmio");

devm_platform_ioremap_resource() already emits an error message if there
is a problem. So please don't add another message here.

> +	clk = devm_clk_get_enabled(&pdev->dev, NULL);
> +	if (IS_ERR(clk))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(clk), "unable to get the clock");
> +
> +	/*
> +	 * uses the 24MHz system clock on all existing devices, can only
> +	 * happen if the device tree is broken
> +	 */
> +	fpwm->clkrate = clk_get_rate(clk);
> +	if (fpwm->clkrate > NSEC_PER_SEC)
> +		return dev_err_probe(&pdev->dev, -EINVAL, "pwm clock out of range");

This check is done to prevent an overflow in .apply, right? Please point
that out in a comment.

> +	fpwm->chip.dev = &pdev->dev;
> +	fpwm->chip.npwm = 1;
> +	fpwm->chip.ops = &apple_pwm_ops;
> +
> +	ret = devm_pwmchip_add(&pdev->dev, &fpwm->chip);
> +	if (ret < 0)
> +		return dev_err_probe(&pdev->dev, ret, "unable to add pwm chip");
> +
> +	return 0;
> +}
> +
> [...]

Best regards
Uwe

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

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Re: [PATCH v6 2/5] pwm: Add Apple PWM controller

[Sasha Finkelstein]

On Wed, 11 Jan 2023 at 02:06, Uwe Kleine-König
<u.kleine-koenig@pengutronix.de> wrote:
> > + * Limitations:
> > + * - The writes to cycle registers are shadowed until a write to
> > + *   the control register.
> > + * - If both OFF_CYCLES and ON_CYCLES are set to 0, the output
> > + *   is a constant off signal.
>
> How does the PWM behave with *APPLE_PWM_CTRLAPPLE_PWM_CTRL = 0?
> (typically: drives constant low)
>
APPLE_PWM_CTRL = 0 implies that the APPLE_CTRL_ENABLE bit is set low, which
turns off the pwm signal (constant low). I do not think that it is
necessary to explicitly
specify that case in the comments.

> Can you please rename such that the (maybe new) name for APPLE_PWM_CTRL
> is a prefix for the (maybe new) APPLE_CTRL_ENABLE and the other register
> bit definitions?
To make sure, you want the register named APPLE_PWM_CTRL, and the bits named
APPLE_PWM_CTRL_ENABLE, APPLE_PWM_CTRL_MODE and so on?

Re: [PATCH v6 2/5] pwm: Add Apple PWM controller

[Uwe Kleine-König]

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On Fri, Jan 13, 2023 at 09:25:08PM +0300, Sasha Finkelstein wrote:
> On Wed, 11 Jan 2023 at 02:06, Uwe Kleine-König
> <u.kleine-koenig@pengutronix.de> wrote:
> > > + * Limitations:
> > > + * - The writes to cycle registers are shadowed until a write to
> > > + *   the control register.
> > > + * - If both OFF_CYCLES and ON_CYCLES are set to 0, the output
> > > + *   is a constant off signal.
> >
> > How does the PWM behave with *APPLE_PWM_CTRLAPPLE_PWM_CTRL = 0?
> > (typically: drives constant low)
> >
> APPLE_PWM_CTRL = 0 implies that the APPLE_CTRL_ENABLE bit is set low, which
> turns off the pwm signal (constant low). I do not think that it is
> necessary to explicitly
> specify that case in the comments.

This is an information that I want to have available. Ideally easily
greppable by using the format that other drivers use for that, too.
(The command I usually use is:

	sed -rn '/Limitations:/,/\*\/?$/p' drivers/pwm/*.c

so if you make sure your info is added accordingly that would be good.)

This is useful to answer questions like: Can I reasonably expect that a
disabled PWM respects the configured polarity.

> > Can you please rename such that the (maybe new) name for APPLE_PWM_CTRL
> > is a prefix for the (maybe new) APPLE_CTRL_ENABLE and the other register
> > bit definitions?
> To make sure, you want the register named APPLE_PWM_CTRL, and the bits named
> APPLE_PWM_CTRL_ENABLE, APPLE_PWM_CTRL_MODE and so on?

Yes.

Best regards
Uwe

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

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