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>

1 files changed, 139 insertions, 0 deletions

diff --git a/drivers/gpu/drm/nouveau/nouveau_led.c b/drivers/gpu/drm/nouveau/nouveau_led.c
new file mode 100644
index 0000000..3e2f1b6
--- /dev/null
+++ b/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;
+	}
+}