[RFC] PWM: Add support for pwm-bcm2835
Johannes Thumshirn
morbidrsa at gmail.com
Sat Sep 21 03:09:02 PDT 2013
Add support for the PWM controller of the BCM2835 SoC found on Raspberry PI
The driver isn't as much tested as I wanted it to be and devicetree
support is still missing, but I thought it would be nice to have some
comments if I'm in the right direction.
Signed-off-by: Johannes Thumshirn <morbidrsa at gmail.com>
---
drivers/pwm/Kconfig | 8 ++
drivers/pwm/Makefile | 1 +
drivers/pwm/pwm-bcm2835.c | 275 ++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 284 insertions(+)
create mode 100644 drivers/pwm/pwm-bcm2835.c
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 75840b5..5417159 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -224,4 +224,12 @@ config PWM_VT8500
To compile this driver as a module, choose M here: the module
will be called pwm-vt8500.
+config PWM_BCM2835
+ tristate "BCM2835 PWM support"
+ help
+ Generic PWM framework driver for bcm2835 found on the Rasperry PI
+
+ To compile this driver as a module, choose M here: the module will be
+ called pwm-bcm2835
+
endif
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 77a8c18..0cf8d4d 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -20,3 +20,4 @@ obj-$(CONFIG_PWM_TIPWMSS) += pwm-tipwmss.o
obj-$(CONFIG_PWM_TWL) += pwm-twl.o
obj-$(CONFIG_PWM_TWL_LED) += pwm-twl-led.o
obj-$(CONFIG_PWM_VT8500) += pwm-vt8500.o
+obj-$(CONFIG_PWM_BCM2835) += pwm-bcm2835.o
diff --git a/drivers/pwm/pwm-bcm2835.c b/drivers/pwm/pwm-bcm2835.c
new file mode 100644
index 0000000..8a64666
--- /dev/null
+++ b/drivers/pwm/pwm-bcm2835.c
@@ -0,0 +1,275 @@
+/*
+ * BCM2835 PWM driver
+ *
+ * Derived from the Tegra PWM driver by NVIDIA Corporation.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * 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.
+ */
+
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/pwm.h>
+
+#define NPWM 2
+
+/* Address Mappings (offsets) from Broadcom BCM2835 ARM Periperals Manual
+ * Section 9.6 Page 141ff
+ */
+#define BCM2835_PWM_CTL 0x00 /* Control register */
+#define BCM2835_PWM_STA 0x04 /* Status register */
+#define BCM2835_PWM_DMAC 0x08 /* PWM DMA Configuration */
+#define BCM2835_PWM_RNG1 0x10 /* PWM Channel 1 Range */
+#define BCM2835_PWM_DAT1 0x14 /* PWM Channel 1 Data */
+#define BCM2835_PWM_FIF1 0x18 /* PWM FIFO Input */
+#define BCM2835_PWM_RNG2 0x20 /* PWM Channel 2 Range */
+#define BCM2835_PWM_DAT2 0x24 /* PWM Channel 2 Data */
+
+/* Control registers 0 and 1 are mirrored on a distance of 4 bits */
+#define HWPWM(x) ((x) << 4)
+
+/* TODO: We only need this register set once and use HWPWM macro to
+ * access 2nd output
+ */
+/* Control Register Bits */
+#define BCM2835_PWM_CTL_PWEN1 BIT(0) /* Channel 1 enable (RW) */
+#define BCM2835_PWM_CTL_MODE1 BIT(1) /* Channel 1 mode (RW) */
+#define BCM2835_PWM_CTL_RPTL1 BIT(2) /* Channel 1 repeat last data (RW) */
+#define BCM2835_PWM_CTL_SBIT1 BIT(3) /* Channel 1 silence bit (RW) */
+#define BCM2835_PWM_CTL_POLA1 BIT(4) /* Channel 1 polarity (RW) */
+#define BCM2835_PWM_CTL_USEF1 BIT(5) /* Channel 1 use FIFO (RW) */
+#define BCM2835_PWM_CTL_CLRF1 BIT(6) /* Channel 1 clear FIFO (RO) */
+#define BCM2835_PWM_CTL_MSEN1 BIT(7) /* Channel 1 M/S enable (RW) */
+#define BCM2835_PWM_CTL_PWEN2 BIT(8) /* Channel 2 enable (RW) */
+#define BCM2835_PWM_CTL_MODE2 BIT(9) /* Channel 2 mode (RW) */
+#define BCM2835_PWM_CTL_RPTL2 BIT(10) /* Channel 2 repeat last data (RW) */
+#define BCM2835_PWM_CTL_SBIT2 BIT(11) /* Channel 2 silence bit (RW) */
+#define BCM2835_PWM_CTL_POLA2 BIT(12) /* Channel 2 polarity (RW) */
+#define BCM2835_PWM_CTL_USEF2 BIT(13) /* Channel 2 use FIFO (RW) */
+/* Bit 14 is reserved */
+#define BCM2835_PWM_MSEN2 BIT(15) /* Channel 2 M/S enable (RW) */
+/* Bits 16 - 31 are reserved */
+
+/* Status Register Bits */
+#define BCM2835_PWM_STA_FULL1 BIT(0) /* FIFO full flag (RW) */
+#define BCM2835_PWM_STA_EMPT1 BIT(1) /* FIFO empty flag (RW) */
+#define BCM2835_PWM_STA_WERR1 BIT(2) /* FIFO write error flag (RW) */
+#define BCM2835_PWM_STA_RERR1 BIT(3) /* FIFO read error flag (RW) */
+#define BCM2835_PWM_STA_GAPO1 BIT(4) /* Channel 1 gap occured (RW) */
+#define BCM2835_PWM_STA_GAPO2 BIT(5) /* Channel 2 gap occured (RW) */
+#define BCM2835_PWM_STA_GAPO3 BIT(6) /* Channel 3 gap occured (RW) */
+#define BCM2835_PWM_STA_GAPO4 BIT(7) /* Channel 4 gap occured (RW) */
+#define BCM2835_PWM_STA_BERR BIT(8) /* Bus error flag (RW) */
+#define BCM2835_PWM_STA_STA1 BIT(9) /* Channel 1 state (RW) */
+#define BCM2835_PWM_STA_STA2 BIT(10) /* Channel 1 state (RW) */
+#define BCM2835_PWM_STA_STA3 BIT(11) /* Channel 1 state (RW) */
+#define BCM2835_PWM_STA_STA4 BIT(12) /* Channel 1 state (RW) */
+/* Bits 13 - 31 are reserved */
+
+struct bcm2835_pwm_dev {
+ struct pwm_chip chip;
+ struct device *dev;
+ struct clk *clk;
+ void __iomem *mmio_base;
+};
+
+static inline struct bcm2835_pwm_dev *to_bcm(struct pwm_chip *chip)
+{
+ return container_of(chip, struct bcm2835_pwm_dev, chip);
+}
+
+static inline u32 bcm2835_readl(struct bcm2835_pwm_dev *chip,
+ unsigned int hwpwm, unsigned int num)
+{
+ num <<= HWPWM(hwpwm);
+ return readl(chip->mmio_base + num);
+}
+
+static inline void bcm2835_writel(struct bcm2835_pwm_dev *chip,
+ unsigned int hwpwm, unsigned int num,
+ unsigned long val)
+{
+ num <<= HWPWM(hwpwm);
+ writel(val, chip->mmio_base + num);
+}
+
+static int bcm2835_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
+ int duty_ns, int period_ns)
+{
+ struct bcm2835_pwm_dev *bcm = to_bcm(chip);
+
+ if (WARN_ON(!bcm))
+ return -ENODEV;
+
+ if (duty_ns < 1) {
+ dev_err(bcm->dev, "duty is out of range: %d < 1\n", duty_ns);
+ return -ERANGE;
+ }
+
+ if (period_ns < 1) {
+ dev_err(bcm->dev, "period is out of range: %d < 1\n",
+ period_ns);
+ return -ERANGE;
+ }
+
+ /* disable PWM */
+ bcm2835_writel(bcm, pwm->hwpwm, BCM2835_PWM_CTL, 0);
+
+ /* write period */
+ bcm2835_writel(bcm, pwm->hwpwm, BCM2835_PWM_RNG1, period_ns);
+
+ /* write duty */
+ bcm2835_writel(bcm, pwm->hwpwm, BCM2835_PWM_DAT1, duty_ns);
+
+ /* start PWM */
+ bcm2835_writel(bcm, pwm->hwpwm, BCM2835_PWM_CTL, BCM2835_PWM_CTL_PWEN1);
+
+ return 0;
+}
+
+static int bcm2835_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+ struct bcm2835_pwm_dev *bcm = to_bcm(chip);
+ int rc = 0;
+ u32 val;
+
+ if (WARN_ON(!bcm))
+ return -ENODEV;
+
+ rc = clk_prepare_enable(bcm->clk);
+ if (rc < 0)
+ return rc;
+
+ val = bcm2835_readl(bcm, pwm->hwpwm, BCM2835_PWM_CTL);
+ val |= BCM2835_PWM_CTL_PWEN1;
+ bcm2835_writel(bcm, pwm->hwpwm, BCM2835_PWM_CTL, val);
+
+ return 0;
+}
+
+static void bcm2835_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+ struct bcm2835_pwm_dev *bcm = to_bcm(chip);
+ u32 val;
+
+ if (WARN_ON(!bcm))
+ return;
+
+ val = bcm2835_readl(bcm, pwm->hwpwm, BCM2835_PWM_CTL);
+ val &= ~BCM2835_PWM_CTL_PWEN1;
+ bcm2835_writel(bcm, pwm->hwpwm, BCM2835_PWM_CTL, val);
+
+ clk_disable_unprepare(bcm->clk);
+}
+
+static int bcm2835_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
+ enum pwm_polarity polarity)
+{
+ struct bcm2835_pwm_dev *bcm = to_bcm(chip);
+ u32 val;
+
+ if (WARN_ON(!bcm))
+ return -ENODEV;
+
+ val = bcm2835_readl(bcm, pwm->hwpwm, BCM2835_PWM_CTL);
+
+ if (polarity == PWM_POLARITY_NORMAL)
+ val |= BCM2835_PWM_CTL_POLA1;
+ else
+ val &= ~BCM2835_PWM_CTL_POLA1;
+
+ return 0;
+}
+
+static const struct pwm_ops bcm2835_pwm_ops = {
+ .config = bcm2835_pwm_config,
+ .enable = bcm2835_pwm_enable,
+ .disable = bcm2835_pwm_disable,
+ .set_polarity = bcm2835_set_polarity,
+};
+
+static int bcm2835_pwm_probe(struct platform_device *pdev)
+{
+ struct bcm2835_pwm_dev *bcm;
+ struct resource *r;
+ int ret;
+
+ bcm = devm_kzalloc(&pdev->dev, sizeof(*bcm), GFP_KERNEL);
+ if (!bcm)
+ return -ENOMEM;
+
+ r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (!r) {
+ dev_err(&pdev->dev, "no memory resource defined\n");
+ return -ENODEV;
+ }
+
+ bcm->mmio_base = devm_ioremap_resource(&pdev->dev, r);
+ if (IS_ERR(bcm->mmio_base))
+ return PTR_ERR(bcm->mmio_base);
+
+ bcm->clk = devm_clk_get(&pdev->dev, NULL);
+ if (IS_ERR(bcm->clk))
+ return PTR_ERR(bcm->clk);
+
+ clk_prepare_enable(bcm->clk);
+
+ bcm->chip.ops = &bcm2835_pwm_ops;
+ bcm->chip.dev = &pdev->dev;
+ bcm->chip.base = -1;
+ bcm->chip.npwm = NPWM;
+
+ ret = pwmchip_add(&bcm->chip);
+ if (ret < 0)
+ return ret;
+
+ platform_set_drvdata(pdev, bcm);
+
+ return 0;
+}
+
+static int bcm2835_pwm_remove(struct platform_device *pdev)
+{
+ struct bcm2835_pwm_dev *bcm = platform_get_drvdata(pdev);
+
+ if (WARN_ON(!bcm))
+ return -ENODEV;
+
+ clk_disable_unprepare(bcm->clk);
+
+ return pwmchip_remove(&bcm->chip);
+}
+
+static const struct of_device_id bcm2835_pwm_of_match[] = {
+ { .compatible = "brcm,bcm2835-pwm" },
+ {},
+};
+
+MODULE_DEVICE_TABLE(of, bcm2835_pwm_of_match);
+
+static struct platform_driver bcm2835_pwm_driver = {
+ .probe = bcm2835_pwm_probe,
+ .remove = bcm2835_pwm_remove,
+ .driver = {
+ .name = "pwm-bcm2835",
+ .owner = THIS_MODULE,
+ .of_match_table = bcm2835_pwm_of_match,
+ },
+};
+
+module_platform_driver(bcm2835_pwm_driver);
+
+MODULE_AUTHOR("Johannes Thumshirn <morbidrsa at gmail.com>");
+MODULE_DESCRIPTION("BCM2835 PWM driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:pwm-bcm2835");
--
1.8.4
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