drm/nouveau/drm/nouveau: add a LED driver for the NVIDIA logo

We received a donation of a Titan which has this useless feature
allowing users to control the brightness of the LED behind the
logo of NVIDIA. In the true spirit of open source, let's expose
that to the users of very expensive cards!

This patch hooks up this LED/PWM to the LED subsystem which allows
blinking it in sync with cpu/disk/network/whatever activity (heartbeat
is quite nice!). Users may also implement some breathing effect or
morse code support in the userspace if they feel like it.

v2:
 - surround the use of the LED framework with ifdef CONFIG_LEDS_CLASS

v3:
 - avoid using ifdefs everywhere, follow the recommendations of
   /doc/Documentation/CodingStyle. Suggested by Emil Velikov.

v4 (Ben):
 - squashed series of fixes from ml

Signed-off-by: Martin Peres <martin.peres@free.fr>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/Kbuild

@@ -22,6 +22,7 @@ nouveau-$(CONFIG_DEBUG_FS) += nouveau_debugfs.o
 nouveau-y += nouveau_drm.o
 nouveau-y += nouveau_hwmon.o
 nouveau-$(CONFIG_COMPAT) += nouveau_ioc32.o
+nouveau-$(CONFIG_LEDS_CLASS) += nouveau_led.o
 nouveau-y += nouveau_nvif.o
 nouveau-$(CONFIG_NOUVEAU_PLATFORM_DRIVER) += nouveau_platform.o
 nouveau-y += nouveau_usif.o # userspace <-> nvif

drivers/gpu/drm/nouveau/include/nvkm/subdev/bios/gpio.h

@@ -6,6 +6,7 @@ enum dcb_gpio_func_name {
 	DCB_GPIO_TVDAC1 = 0x2d,
 	DCB_GPIO_FAN = 0x09,
 	DCB_GPIO_FAN_SENSE = 0x3d,
+	DCB_GPIO_LOGO_LED_PWM = 0x84,
 	DCB_GPIO_UNUSED = 0xff,
 	DCB_GPIO_VID0 = 0x04,
 	DCB_GPIO_VID1 = 0x05,

drivers/gpu/drm/nouveau/nouveau_drm.c

@@ -47,6 +47,7 @@
 #include "nouveau_ttm.h"
 #include "nouveau_gem.h"
 #include "nouveau_vga.h"
+#include "nouveau_led.h"
 #include "nouveau_hwmon.h"
 #include "nouveau_acpi.h"
 #include "nouveau_bios.h"
@@ -475,6 +476,7 @@ nouveau_drm_load(struct drm_device *dev, unsigned long flags)
 	nouveau_hwmon_init(dev);
 	nouveau_accel_init(drm);
 	nouveau_fbcon_init(dev);
+	nouveau_led_init(dev);
 
 	if (nouveau_runtime_pm != 0) {
 		pm_runtime_use_autosuspend(dev->dev);
@@ -510,6 +512,7 @@ nouveau_drm_unload(struct drm_device *dev)
 		pm_runtime_forbid(dev->dev);
 	}
 
+	nouveau_led_fini(dev);
 	nouveau_fbcon_fini(dev);
 	nouveau_accel_fini(drm);
 	nouveau_hwmon_fini(dev);
@@ -561,6 +564,8 @@ nouveau_do_suspend(struct drm_device *dev, bool runtime)
 	struct nouveau_cli *cli;
 	int ret;
 
+	nouveau_led_suspend(dev);
+
 	if (dev->mode_config.num_crtc) {
 		NV_INFO(drm, "suspending console...\n");
 		nouveau_fbcon_set_suspend(dev, 1);
@@ -649,6 +654,8 @@ nouveau_do_resume(struct drm_device *dev, bool runtime)
 		nouveau_fbcon_set_suspend(dev, 0);
 	}
 
+	nouveau_led_resume(dev);
+
 	return 0;
 }
 

drivers/gpu/drm/nouveau/nouveau_drv.h

@@ -166,6 +166,9 @@ struct nouveau_drm {
 	struct nouveau_hwmon *hwmon;
 	struct nouveau_debugfs *debugfs;
 
+	/* led management */
+	struct nouveau_led *led;
+
 	/* display power reference */
 	bool have_disp_power_ref;
 

drivers/gpu/drm/nouveau/nouveau_led.c

@@ -0,0 +1,139 @@
+/*
+ * Copyright (C) 2016 Martin Peres
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE COPYRIGHT OWNER(S) AND/OR ITS SUPPLIERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+/*
+ * Authors:
+ *  Martin Peres <martin.peres@free.fr>
+ */
+
+#include <linux/leds.h>
+
+#include "nouveau_led.h"
+#include <nvkm/subdev/gpio.h>
+
+static enum led_brightness
+nouveau_led_get_brightness(struct led_classdev *led)
+{
+	struct drm_device *drm_dev = container_of(led, struct nouveau_led, led)->dev;
+	struct nouveau_drm *drm = nouveau_drm(drm_dev);
+	struct nvif_object *device = &drm->device.object;
+	u32 div, duty;
+
+	div =  nvif_rd32(device, 0x61c880) & 0x00ffffff;
+	duty = nvif_rd32(device, 0x61c884) & 0x00ffffff;
+
+	if (div > 0)
+		return duty * LED_FULL / div;
+	else
+		return 0;
+}
+
+static void
+nouveau_led_set_brightness(struct led_classdev *led, enum led_brightness value)
+{
+	struct drm_device *drm_dev = container_of(led, struct nouveau_led, led)->dev;
+	struct nouveau_drm *drm = nouveau_drm(drm_dev);
+	struct nvif_object *device = &drm->device.object;
+
+	u32 input_clk = 27e6; /* PDISPLAY.SOR[1].PWM is connected to the crystal */
+	u32 freq = 100; /* this is what nvidia uses and it should be good-enough */
+	u32 div, duty;
+
+	div = input_clk / freq;
+	duty = value * div / LED_FULL;
+
+	/* for now, this is safe to directly poke those registers because:
+	 *  - A: nvidia never puts the logo led to any other PWM controler
+	 *       than PDISPLAY.SOR[1].PWM.
+	 *  - B: nouveau does not touch these registers anywhere else
+	 */
+	nvif_wr32(device, 0x61c880, div);
+	nvif_wr32(device, 0x61c884, 0xc0000000 | duty);
+}
+
+
+int
+nouveau_led_init(struct drm_device *dev)
+{
+	struct nouveau_drm *drm = nouveau_drm(dev);
+	struct nvkm_gpio *gpio = nvxx_gpio(&drm->device);
+	struct dcb_gpio_func logo_led;
+	int ret;
+
+	if (!gpio)
+		return 0;
+
+	/* check that there is a GPIO controlling the logo LED */
+	if (nvkm_gpio_find(gpio, 0, DCB_GPIO_LOGO_LED_PWM, 0xff, &logo_led))
+		return 0;
+
+	drm->led = kzalloc(sizeof(*drm->led), GFP_KERNEL);
+	if (!drm->led)
+		return -ENOMEM;
+	drm->led->dev = dev;
+
+	drm->led->led.name = "nvidia-logo";
+	drm->led->led.max_brightness = 255;
+	drm->led->led.brightness_get = nouveau_led_get_brightness;
+	drm->led->led.brightness_set = nouveau_led_set_brightness;
+
+	ret = led_classdev_register(dev->dev, &drm->led->led);
+	if (ret) {
+		kfree(drm->led);
+		return ret;
+	}
+
+	return 0;
+}
+
+void
+nouveau_led_suspend(struct drm_device *dev)
+{
+	struct nouveau_drm *drm = nouveau_drm(dev);
+
+	if (drm->led)
+		led_classdev_suspend(&drm->led->led);
+}
+
+void
+nouveau_led_resume(struct drm_device *dev)
+{
+	struct nouveau_drm *drm = nouveau_drm(dev);
+
+	if (drm->led)
+		led_classdev_resume(&drm->led->led);
+}
+
+void
+nouveau_led_fini(struct drm_device *dev)
+{
+	struct nouveau_drm *drm = nouveau_drm(dev);
+
+	if (drm->led) {
+		led_classdev_unregister(&drm->led->led);
+		kfree(drm->led);
+		drm->led = NULL;
+	}
+}

drivers/gpu/drm/nouveau/nouveau_led.h

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2015 Martin Peres
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Authors: Martin Peres <martin.peres@free.fr>
+ */
+
+#ifndef __NOUVEAU_LED_H__
+#define __NOUVEAU_LED_H__
+
+#include "nouveau_drv.h"
+
+struct led_classdev;
+
+struct nouveau_led {
+	struct drm_device *dev;
+
+	struct led_classdev led;
+};
+
+static inline struct nouveau_led *
+nouveau_led(struct drm_device *dev)
+{
+	return nouveau_drm(dev)->led;
+}
+
+/* nouveau_led.c */
+#if IS_ENABLED(CONFIG_LEDS_CLASS)
+int  nouveau_led_init(struct drm_device *dev);
+void nouveau_led_suspend(struct drm_device *dev);
+void nouveau_led_resume(struct drm_device *dev);
+void nouveau_led_fini(struct drm_device *dev);
+#else
+static inline int  nouveau_led_init(struct drm_device *dev) { return 0; };
+static inline void nouveau_led_suspend(struct drm_device *dev) { };
+static inline void nouveau_led_resume(struct drm_device *dev) { };
+static inline void nouveau_led_fini(struct drm_device *dev) { };
+#endif
+
+#endif