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PWM and keyboard backlight driver for ARM Macs

PATCH Superseded Sasha Finkelstein 3 participants 8 messages Dec 9, 2022 – Dec 21, 2022

Subsystems (3)
Device tree bindings PWM Arm/Apple machine support

v4 of 9 Superseded Latest is v9 →

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Sasha Finkelstein

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#0 lore raw

v4 cover PWM and keyboard backlight driver for ARM Macs

Hi,

This is the v4 of the patch series to add PWM and keyboard backlight driver for ARM macs.

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:
Addressing the review comments.

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

Sasha Finkelstein (4):
dt-bindings: pwm: Add Apple PWM controller
pwm: Add Apple PWM controller
arm64: dts: apple: t8103: Add PWM controller
MAINTAINERS: Add entries for Apple PWM driver

 .../bindings/pwm/apple,s5l-fpwm.yaml          |  51 ++++++
 MAINTAINERS                                   |   2 +
 arch/arm64/boot/dts/apple/t8103-j293.dts      |  19 +++
 arch/arm64/boot/dts/apple/t8103-j313.dts      |  19 +++
 arch/arm64/boot/dts/apple/t8103.dtsi          |   9 ++
 drivers/pwm/Kconfig                           |  12 ++
 drivers/pwm/Makefile                          |   1 +
 drivers/pwm/pwm-apple.c                       | 150 ++++++++++++++++++
 8 files changed, 263 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/pwm/apple,s5l-fpwm.yaml
 create mode 100644 drivers/pwm/pwm-apple.c
Signature · 1 line
2.37.1 (Apple Git-137.1)
author
#1 lore raw

PATCH v4 1/4 dt-bindings: pwm: Add Apple PWM controller

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

Signed-off-by Sasha Finkelstein <[email protected]>
Reviewed-by Krzysztof Kozlowski <[email protected]>
Acked-by Sven Peter <[email protected]>
---
 .../bindings/pwm/apple,s5l-fpwm.yaml          | 51 +++++++++++++++++++
 1 file changed, 51 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/pwm/apple,s5l-fpwm.yaml
Documentation/devicetree/bindings/pwm/apple,s5l-fpwm.yaml new file +51 -0
new file mode 100644
index 000000000000..142157bff0cd
@@ -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:
+  - [email protected]
+  - Sasha Finkelstein <[email protected]>
+
+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>;
+    };
Signature · 1 line
2.37.1 (Apple Git-137.1)
author
#2 lore raw

PATCH v4 2/4 pwm: Add Apple PWM controller

In reply to Sasha Finkelstein

Adds the Apple PWM controller driver.

Signed-off-by Sasha Finkelstein <[email protected]>
Acked-by Sven Peter <[email protected]>
---
 drivers/pwm/Kconfig     |  12 ++++
 drivers/pwm/Makefile    |   1 +
 drivers/pwm/pwm-apple.c | 150 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 163 insertions(+)
 create mode 100644 drivers/pwm/pwm-apple.c
drivers/pwm/Kconfig +12 -0
index 60d13a949bc5..c3be11468414 100644
@@ -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
drivers/pwm/Makefile +1 -0
index 7bf1a29f02b8..19899b912e00 100644
@@ -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
drivers/pwm/pwm-apple.c new file +150 -0

150 lines not on this page · raw message

Signature · 1 line
2.37.1 (Apple Git-137.1)
#3 lore raw

Re: [PATCH v4 2/4] pwm: Add Apple PWM controller

Hello,

over all the driver looks good. Just a few smaller issues below.

I wonder if it's a good idea to call this driver "apple". SoC vendors seem to reinvent their peripherals (or buy them somewhere else) for their different generations of processors. Maybe call it "apple-s5l" already today and not only when the next generation SoC appears? (I don't feel strong here, if you want to delay that renaming until there is an incompatible SoC that's fine for me.)

Quoted 16 lines · Sasha Finkelstein
drivers/pwm/pwm-apple.c new file +10 -0
new file mode 100644
index 000000000000..a85fecb20105
@@ -0,0 +1,150 @@
+// 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.
+ */

drivers/pwm/pwm-apple.c line 20

Quoted 10 lines
drivers/pwm/pwm-apple.c new file +10 -0
+
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/io.h>
+#include <linux/clk.h>
+#include <linux/pm_runtime.h>
+#include <linux/math64.h>

I didn't test, but I think you don't need pm_runtime.h here. Also maybe the of headers are not needed?

drivers/pwm/pwm-apple.c line 31

Quoted 10 lines
drivers/pwm/pwm-apple.c new file +10 -0
+#define APPLE_PWM_CONTROL     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)

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.

Quoted 7 lines
drivers/pwm/pwm-apple.c new file +7 -0
+
+struct apple_pwm {
+	struct pwm_chip chip;
+	void __iomem *base;
+	u64 clkrate;
+};
+

drivers/pwm/pwm-apple.c line 48

Quoted 10 lines
drivers/pwm/pwm-apple.c new file +10 -0
+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;
+	u64 on_cycles, off_cycles;

The declaration can move into the if block below.

Quoted 11 lines
drivers/pwm/pwm-apple.c new file +11 -0
+
+	fpwm = to_apple_pwm(chip);
+	if (state->enabled) {
+		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)

drivers/pwm/pwm-apple.c line 69

Quoted 10 lines
drivers/pwm/pwm-apple.c new file +10 -0
+			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_CONTROL);
+	} else {
+		writel(0, fpwm->base + APPLE_PWM_CONTROL);
+	}
+	return 0;

Assuming clkrate = 24000000, I wonder what happens if (duty_cycle and) period are so small that on_cycles and off_cycles are both zero. How does the hardware behave in this case?

Quoted 9 lines
drivers/pwm/pwm-apple.c new file +9 -0
+}
+
+static void 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);

drivers/pwm/pwm-apple.c line 88

Quoted 10 lines
drivers/pwm/pwm-apple.c new file +10 -0
+
+	ctrl = readl(fpwm->base + APPLE_PWM_CONTROL);
+	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;
+	state->duty_cycle = mul_u64_u64_div_u64(on_cycles, NSEC_PER_SEC, fpwm->clkrate);
+	state->period = mul_u64_u64_div_u64(off_cycles + on_cycles,
+					    NSEC_PER_SEC, fpwm->clkrate);

Wrong rounding direction, you need to round up. Did you test with PWM_DEBUG on? This should point out the more obvious cases. Assuming clkrate = 24000000 for example setting .duty_cycle = 3 should trigger a warning.

Unfortunately there is no variant of mul_u64_u64_div_u64 that rounds up, maybe we need to introduce one.

drivers/pwm/pwm-apple.c line 88

Quoted 1 line
drivers/pwm/pwm-apple.c new file +1 -0
+}

Best regards
Uwe

Signature · 2 lines
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |
#4 lore raw

Re: [PATCH v4 2/4] pwm: Add Apple PWM controller

Quoted 10 lines · Uwe Kleine-König

Hello,

over all the driver looks good. Just a few smaller issues below.

I wonder if it's a good idea to call this driver "apple". SoC vendors seem to reinvent their peripherals (or buy them somewhere else) for their different generations of processors. Maybe call it "apple-s5l" already today and not only when the next generation SoC appears? (I don't feel strong here, if you want to delay that renaming until there is an incompatible SoC that's fine for me.)

Well... considering s5l refers to the s5l8920x, the SoC used in the iPhone 3GS released in 2009, and here we are with the M1 13 years later and it's still the same, I think we're doing pretty well here.

(Apple doesn't reinvent their peripherals nearly as often as other vendors).

- Hector

#5 lore raw

Re: [PATCH v4 2/4] pwm: Add Apple PWM controller

In reply to Sasha Finkelstein
Quoted 91 lines · Sasha Finkelstein

Adds the Apple PWM controller driver.

Signed-off-by Sasha Finkelstein <[email protected]>
Acked-by Sven Peter <[email protected]>
---
 drivers/pwm/Kconfig     |  12 ++++
 drivers/pwm/Makefile    |   1 +
 drivers/pwm/pwm-apple.c | 150 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 163 insertions(+)
 create mode 100644 drivers/pwm/pwm-apple.c
drivers/pwm/Kconfig +12 -0
index 60d13a949bc5..c3be11468414 100644
@@ -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
drivers/pwm/Makefile +1 -0
index 7bf1a29f02b8..19899b912e00 100644
@@ -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
drivers/pwm/pwm-apple.c new file +39 -0
new file mode 100644
index 000000000000..a85fecb20105
@@ -0,0 +1,150 @@
+// 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.
+ */
+
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/io.h>
+#include <linux/clk.h>
+#include <linux/pm_runtime.h>
+#include <linux/math64.h>
+
+#define APPLE_PWM_CONTROL     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)

drivers/pwm/pwm-apple.c line 49

Quoted 10 lines
drivers/pwm/pwm-apple.c new file +10 -0
+{
+	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;
+	u64 on_cycles, off_cycles;
+

polarity handling is missing here and in .get_state(). I assume you want:

	if (state->polarity == PWM_POLARITY_INVERSED)
		return -EINVAL;

here and

	state->polarity = PWM_POLARITY_NORMAL;

in .get_state().

Quoted 11 lines
drivers/pwm/pwm-apple.c new file +11 -0
+	fpwm = to_apple_pwm(chip);
+	if (state->enabled) {
+		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;

drivers/pwm/pwm-apple.c line 70

Quoted 10 lines
drivers/pwm/pwm-apple.c new file +10 -0
+
+		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_CONTROL);
+	} else {
+		writel(0, fpwm->base + APPLE_PWM_CONTROL);
+	}
+	return 0;
+}

Best regards
Uwe

Signature · 2 lines
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |
author
#6 lore raw

PATCH v4 3/4 arm64: dts: apple: t8103: Add PWM controller

In reply to Sasha Finkelstein

Adds PWM controller and keyboard backlight bindings for M1 MacBooks

Signed-off-by Sasha Finkelstein <[email protected]>
Acked-by Sven Peter <[email protected]>
---
 arch/arm64/boot/dts/apple/t8103-j293.dts | 19 +++++++++++++++++++
 arch/arm64/boot/dts/apple/t8103-j313.dts | 19 +++++++++++++++++++
 arch/arm64/boot/dts/apple/t8103.dtsi     |  9 +++++++++
 3 files changed, 47 insertions(+)
arch/arm64/boot/dts/apple/t8103-j293.dts +19 -0
index ecb10d237a05..b28d6f9ed3eb 100644
@@ -11,6 +11,7 @@
 
 #include "t8103.dtsi"
 #include "t8103-jxxx.dtsi"
+#include <dt-bindings/leds/common.h>
 
 / {
 	compatible = "apple,j293", "apple,t8103", "apple,arm-platform";

@@ -43,3 +44,21 @@ &i2c2 {
 &i2c4 {
 	status = "okay";
 };
+
+/ {
+	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";
+		};
+	};
+};
+
+&fpwm1 {
+	status = "okay";
+};
arch/arm64/boot/dts/apple/t8103-j313.dts +19 -0
index df741737b8e6..57e75e6ddf63 100644
@@ -11,6 +11,7 @@
 
 #include "t8103.dtsi"
 #include "t8103-jxxx.dtsi"
+#include <dt-bindings/leds/common.h>
 
 / {
 	compatible = "apple,j313", "apple,t8103", "apple,arm-platform";

@@ -35,3 +36,21 @@ &pcie0_dart_2 {
 
 /delete-node/ &port01;
 /delete-node/ &port02;
+
+/ {
+	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";
+		};
+	};
+};
+
+&fpwm1 {
+	status = "okay";
+};
arch/arm64/boot/dts/apple/t8103.dtsi +9 -0
index 51a63b29d404..ccdb26ef6b22 100644
@@ -191,6 +191,15 @@ 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>;
Signature · 1 line
2.37.1 (Apple Git-137.1)
author
#7 lore raw

PATCH v4 4/4 MAINTAINERS: Add entries for Apple PWM driver

In reply to Sasha Finkelstein

Add the MAINTAINERS entries for the driver

Signed-off-by Sasha Finkelstein <[email protected]>
Acked-by Sven Peter <[email protected]>
---
 MAINTAINERS | 2 ++
 1 file changed, 2 insertions(+)
MAINTAINERS +2 -0
index 1daadaa4d48b..86a8265c8e42 100644
@@ -1908,6 +1908,7 @@ 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/clk/clk-apple-nco.c

@@ -1921,6 +1922,7 @@ 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
Signature · 1 line
2.37.1 (Apple Git-137.1)