[U-Boot] [PATCH v3 07/18] tegra: Add support for PWM
Simon Glass
sjg at chromium.org
Thu Jul 12 17:25:07 CEST 2012
The pulse width/frequency modulation peripheral supports generating
a repeating pulse. It is useful for controlling LCD brightness.
Signed-off-by: Simon Glass <sjg at chromium.org>
---
Changes in v3:
- Decode fdt node within the pwm driver
- Introduce concept of a pwm channel, rather than separate peripherals
- Rename pwfm driver to pwm
- Use new proposed upstream pwm binding
arch/arm/cpu/armv7/tegra2/Makefile | 1 +
arch/arm/cpu/armv7/tegra2/pwm.c | 99 ++++++++++++++++++++++++++++++++
arch/arm/include/asm/arch-tegra2/pwm.h | 75 ++++++++++++++++++++++++
include/fdtdec.h | 1 +
lib/fdtdec.c | 1 +
5 files changed, 177 insertions(+), 0 deletions(-)
create mode 100644 arch/arm/cpu/armv7/tegra2/pwm.c
create mode 100644 arch/arm/include/asm/arch-tegra2/pwm.h
diff --git a/arch/arm/cpu/armv7/tegra2/Makefile b/arch/arm/cpu/armv7/tegra2/Makefile
index 80da453..5d271c4 100644
--- a/arch/arm/cpu/armv7/tegra2/Makefile
+++ b/arch/arm/cpu/armv7/tegra2/Makefile
@@ -40,6 +40,7 @@ COBJS-$(CONFIG_TEGRA_PMU) += pmu.o
COBJS-$(CONFIG_USB_EHCI_TEGRA) += usb.o
COBJS-$(CONFIG_TEGRA2_LP0) += crypto.o warmboot.o warmboot_avp.o
COBJS-$(CONFIG_CMD_ENTERRCM) += cmd_enterrcm.o
+COBJS-$(CONFIG_VIDEO_TEGRA) += pwm.o
COBJS := $(COBJS-y)
SRCS := $(SOBJS:.o=.S) $(COBJS:.o=.c)
diff --git a/arch/arm/cpu/armv7/tegra2/pwm.c b/arch/arm/cpu/armv7/tegra2/pwm.c
new file mode 100644
index 0000000..f3b1bdd
--- /dev/null
+++ b/arch/arm/cpu/armv7/tegra2/pwm.c
@@ -0,0 +1,99 @@
+/*
+ * 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);
+}
+
+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;
+ }
+
+ return 0;
+}
diff --git a/arch/arm/include/asm/arch-tegra2/pwm.h b/arch/arm/include/asm/arch-tegra2/pwm.h
new file mode 100644
index 0000000..9e03837
--- /dev/null
+++ b/arch/arm/include/asm/arch-tegra2/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 */
diff --git a/include/fdtdec.h b/include/fdtdec.h
index c30947a..3997bfa 100644
--- a/include/fdtdec.h
+++ b/include/fdtdec.h
@@ -65,6 +65,7 @@ enum fdt_compat_id {
COMPAT_NVIDIA_TEGRA20_EMC, /* Tegra2 memory controller */
COMPAT_NVIDIA_TEGRA20_EMC_TABLE, /* Tegra2 memory timing table */
COMPAT_NVIDIA_TEGRA20_KBC, /* Tegra2 Keyboard */
+ COMPAT_NVIDIA_TEGRA20_PWM, /* Tegra 2 PWM controller */
COMPAT_COUNT,
};
diff --git a/lib/fdtdec.c b/lib/fdtdec.c
index 45a0fcf..40b0aef 100644
--- a/lib/fdtdec.c
+++ b/lib/fdtdec.c
@@ -43,6 +43,7 @@ static const char * const compat_names[COMPAT_COUNT] = {
COMPAT(NVIDIA_TEGRA20_EMC, "nvidia,tegra20-emc"),
COMPAT(NVIDIA_TEGRA20_EMC_TABLE, "nvidia,tegra20-emc-table"),
COMPAT(NVIDIA_TEGRA20_KBC, "nvidia,tegra20-kbc"),
+ COMPAT(NVIDIA_TEGRA20_PWM, "nvidia,tegra20-pwm"),
};
const char *fdtdec_get_compatible(enum fdt_compat_id id)
--
1.7.7.3
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