tegra: Add support for PWM

The pulse width/frequency modulation peripheral supports generating
a repeating pulse. It is useful for controlling LCD brightness.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>

3 files changed, 177 insertions, 0 deletions

diff --git a/arch/arm/cpu/armv7/tegra20/Makefile b/arch/arm/cpu/armv7/tegra20/Makefile
index 09a0314..77cb4d1 100644
--- a/arch/arm/cpu/armv7/tegra20/Makefile
+++ b/arch/arm/cpu/armv7/tegra20/Makefile
@@ -28,6 +28,7 @@ include $(TOPDIR)/config.mk
 LIB	=  $(obj)lib$(SOC).o
 
 COBJS-$(CONFIG_USB_EHCI_TEGRA) += usb.o
+COBJS-$(CONFIG_PWM_TEGRA) += pwm.o
 
 COBJS	:= $(COBJS-y)
 SRCS	:= $(COBJS:.o=.c)
diff --git a/arch/arm/cpu/armv7/tegra20/pwm.c b/arch/arm/cpu/armv7/tegra20/pwm.c
new file mode 100644
index 0000000..b655c5c
--- /dev/null
+++ b/arch/arm/cpu/armv7/tegra20/pwm.c
@@ -0,0 +1,101 @@
+/*
+ * Tegra2 pulse width frequency modulator definitions
+ *
+ * Copyright (c) 2011 The Chromium OS Authors.
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#include <common.h>
+#include <fdtdec.h>
+#include <asm/io.h>
+#include <asm/arch/clock.h>
+#include <asm/arch/pwm.h>
+
+struct pwm_info {
+	struct pwm_ctlr *pwm;		/* Registers for our pwm controller */
+	int pwm_node;			/* PWM device tree node */
+} local;
+
+void pwm_enable(unsigned channel, int rate, int pulse_width, int freq_divider)
+{
+	u32 reg;
+
+	assert(channel < PWM_NUM_CHANNELS);
+
+	/* TODO: Can we use clock_adjust_periph_pll_div() here? */
+	clock_start_periph_pll(PERIPH_ID_PWM, CLOCK_ID_SFROM32KHZ, rate);
+
+	reg = PWM_ENABLE_MASK;
+	reg |= pulse_width << PWM_WIDTH_SHIFT;
+	reg |= freq_divider << PWM_DIVIDER_SHIFT;
+	writel(reg, &local.pwm[channel].control);
+	debug("%s: channel=%d, rate=%d\n", __func__, channel, rate);
+}
+
+int pwm_request(const void *blob, int node, const char *prop_name)
+{
+	int pwm_node;
+	u32 data[3];
+
+	if (fdtdec_get_int_array(blob, node, prop_name, data,
+			ARRAY_SIZE(data))) {
+		debug("%s: Cannot decode PWM property '%s'\n", __func__,
+		      prop_name);
+		return -1;
+	}
+
+	pwm_node = fdt_node_offset_by_phandle(blob, data[0]);
+	if (pwm_node != local.pwm_node) {
+		debug("%s: PWM property '%s' phandle %d not recognised"
+		      "- expecting %d\n", __func__, prop_name, data[0],
+		      local.pwm_node);
+		return -1;
+	}
+	if (data[1] >= PWM_NUM_CHANNELS) {
+		debug("%s: PWM property '%s': invalid channel %u\n", __func__,
+		      prop_name, data[1]);
+		return -1;
+	}
+
+	/*
+	 * TODO: We could maintain a list of requests, but it might not be
+	 * worth it for U-Boot.
+	 */
+	return data[1];
+}
+
+int pwm_init(const void *blob)
+{
+	local.pwm_node = fdtdec_next_compatible(blob, 0,
+						COMPAT_NVIDIA_TEGRA20_PWM);
+	if (local.pwm_node < 0) {
+		debug("%s: Cannot find device tree node\n", __func__);
+		return -1;
+	}
+
+	local.pwm = (struct pwm_ctlr *)fdtdec_get_addr(blob, local.pwm_node,
+						       "reg");
+	if (local.pwm == (struct pwm_ctlr *)FDT_ADDR_T_NONE) {
+		debug("%s: Cannot find pwm reg address\n", __func__);
+		return -1;
+	}
+	debug("Tegra PWM at %p, node %d\n", local.pwm, local.pwm_node);
+
+	return 0;
+}
diff --git a/arch/arm/include/asm/arch-tegra20/pwm.h b/arch/arm/include/asm/arch-tegra20/pwm.h
new file mode 100644
index 0000000..9e03837
--- /dev/null
+++ b/arch/arm/include/asm/arch-tegra20/pwm.h
@@ -0,0 +1,75 @@
+/*
+ * Tegra pulse width frequency modulator definitions
+ *
+ * Copyright (c) 2011 The Chromium OS Authors.
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#ifndef __ASM_ARCH_TEGRA_PWM_H
+#define __ASM_ARCH_TEGRA_PWM_H
+
+/* This is a single PWM channel */
+struct pwm_ctlr {
+	uint control;		/* Control register */
+	uint reserved[3];	/* Space space */
+};
+
+#define PWM_NUM_CHANNELS	4
+
+/* PWM_CONTROLLER_PWM_CSR_0/1/2/3_0 */
+#define PWM_ENABLE_SHIFT	31
+#define PWM_ENABLE_MASK	(0x1 << PWM_ENABLE_SHIFT)
+
+#define PWM_WIDTH_SHIFT	16
+#define PWM_WIDTH_MASK		(0x7FFF << PWM_WIDTH_SHIFT)
+
+#define PWM_DIVIDER_SHIFT	0
+#define PWM_DIVIDER_MASK	(0x1FFF << PWM_DIVIDER_SHIFT)
+
+/**
+ * Program the PWM with the given parameters.
+ *
+ * @param channel	PWM channel to update
+ * @param rate		Clock rate to use for PWM
+ * @param pulse_width	high pulse width: 0=always low, 1=1/256 pulse high,
+ *			n = n/256 pulse high
+ * @param freq_divider	frequency divider value (1 to use rate as is)
+ */
+void pwm_enable(unsigned channel, int rate, int pulse_width, int freq_divider);
+
+/**
+ * Request a pwm channel as referenced by a device tree node.
+ *
+ * This channel can then be passed to pwm_enable().
+ *
+ * @param blob		Device tree blob
+ * @param node		Node containing reference to pwm
+ * @param prop_name	Property name of pwm reference
+ * @return channel number, if ok, else -1
+ */
+int pwm_request(const void *blob, int node, const char *prop_name);
+
+/**
+ * Set up the pwm controller, by looking it up in the fdt.
+ *
+ * @return 0 if ok, -1 if the device tree node was not found or invalid.
+ */
+int pwm_init(const void *blob);
+
+#endif	/* __ASM_ARCH_TEGRA_PWM_H */