pwm: pwm-tiehrpwm: PWM driver support for EHRPWM

Enhanced high resolution PWM module (EHRPWM) hardware can be used to
generate PWM output over 2 channels. This commit adds PWM driver support
for EHRPWM device present on AM33XX SOC. Current implementation supports
simple PWM functionality.

Reviewed-by: Vaibhav Bedia <vaibhav.bedia@ti.com>
Signed-off-by: Philip, Avinash <avinashphilip@ti.com>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>

3 files changed, 422 insertions, 0 deletions

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 2b7db5d..8fc3808 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -86,6 +86,16 @@ config  PWM_TIECAP
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-tiecap.
 
+config  PWM_TIEHRPWM
+	tristate "EHRPWM PWM support"
+	depends on SOC_AM33XX
+	help
+	  PWM driver support for the EHRPWM controller found on AM33XX
+	  TI SOC
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-tiehrpwm.
+
 config PWM_VT8500
 	tristate "vt8500 pwm support"
 	depends on ARCH_VT8500
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 35fee43..e4b2c89 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -7,4 +7,5 @@ obj-$(CONFIG_PWM_PXA)		+= pwm-pxa.o
 obj-$(CONFIG_PWM_SAMSUNG)	+= pwm-samsung.o
 obj-$(CONFIG_PWM_TEGRA)		+= pwm-tegra.o
 obj-$(CONFIG_PWM_TIECAP)	+= pwm-tiecap.o
+obj-$(CONFIG_PWM_TIEHRPWM)	+= pwm-tiehrpwm.o
 obj-$(CONFIG_PWM_VT8500)	+= pwm-vt8500.o
diff --git a/drivers/pwm/pwm-tiehrpwm.c b/drivers/pwm/pwm-tiehrpwm.c
new file mode 100644
index 0000000..010d232
--- /dev/null
+++ b/drivers/pwm/pwm-tiehrpwm.c
@@ -0,0 +1,411 @@
+/*
+ * EHRPWM PWM driver
+ *
+ * Copyright (C) 2012 Texas Instruments, Inc. - http://www.ti.com/
+ *
+ * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/io.h>
+#include <linux/err.h>
+#include <linux/clk.h>
+#include <linux/pm_runtime.h>
+
+/* EHRPWM registers and bits definitions */
+
+/* Time base module registers */
+#define TBCTL			0x00
+#define TBPRD			0x0A
+
+#define TBCTL_RUN_MASK		(BIT(15) | BIT(14))
+#define TBCTL_STOP_NEXT		0
+#define TBCTL_STOP_ON_CYCLE	BIT(14)
+#define TBCTL_FREE_RUN		(BIT(15) | BIT(14))
+#define TBCTL_PRDLD_MASK	BIT(3)
+#define TBCTL_PRDLD_SHDW	0
+#define TBCTL_PRDLD_IMDT	BIT(3)
+#define TBCTL_CLKDIV_MASK	(BIT(12) | BIT(11) | BIT(10) | BIT(9) | \
+				BIT(8) | BIT(7))
+#define TBCTL_CTRMODE_MASK	(BIT(1) | BIT(0))
+#define TBCTL_CTRMODE_UP	0
+#define TBCTL_CTRMODE_DOWN	BIT(0)
+#define TBCTL_CTRMODE_UPDOWN	BIT(1)
+#define TBCTL_CTRMODE_FREEZE	(BIT(1) | BIT(0))
+
+#define TBCTL_HSPCLKDIV_SHIFT	7
+#define TBCTL_CLKDIV_SHIFT	10
+
+#define CLKDIV_MAX		7
+#define HSPCLKDIV_MAX		7
+#define PERIOD_MAX		0xFFFF
+
+/* compare module registers */
+#define CMPA			0x12
+#define CMPB			0x14
+
+/* Action qualifier module registers */
+#define AQCTLA			0x16
+#define AQCTLB			0x18
+#define AQSFRC			0x1A
+#define AQCSFRC			0x1C
+
+#define AQCTL_CBU_MASK		(BIT(9) | BIT(8))
+#define AQCTL_CBU_FRCLOW	BIT(8)
+#define AQCTL_CBU_FRCHIGH	BIT(9)
+#define AQCTL_CBU_FRCTOGGLE	(BIT(9) | BIT(8))
+#define AQCTL_CAU_MASK		(BIT(5) | BIT(4))
+#define AQCTL_CAU_FRCLOW	BIT(4)
+#define AQCTL_CAU_FRCHIGH	BIT(5)
+#define AQCTL_CAU_FRCTOGGLE	(BIT(5) | BIT(4))
+#define AQCTL_PRD_MASK		(BIT(3) | BIT(2))
+#define AQCTL_PRD_FRCLOW	BIT(2)
+#define AQCTL_PRD_FRCHIGH	BIT(3)
+#define AQCTL_PRD_FRCTOGGLE	(BIT(3) | BIT(2))
+#define AQCTL_ZRO_MASK		(BIT(1) | BIT(0))
+#define AQCTL_ZRO_FRCLOW	BIT(0)
+#define AQCTL_ZRO_FRCHIGH	BIT(1)
+#define AQCTL_ZRO_FRCTOGGLE	(BIT(1) | BIT(0))
+
+#define AQSFRC_RLDCSF_MASK	(BIT(7) | BIT(6))
+#define AQSFRC_RLDCSF_ZRO	0
+#define AQSFRC_RLDCSF_PRD	BIT(6)
+#define AQSFRC_RLDCSF_ZROPRD	BIT(7)
+#define AQSFRC_RLDCSF_IMDT	(BIT(7) | BIT(6))
+
+#define AQCSFRC_CSFB_MASK	(BIT(3) | BIT(2))
+#define AQCSFRC_CSFB_FRCDIS	0
+#define AQCSFRC_CSFB_FRCLOW	BIT(2)
+#define AQCSFRC_CSFB_FRCHIGH	BIT(3)
+#define AQCSFRC_CSFB_DISSWFRC	(BIT(3) | BIT(2))
+#define AQCSFRC_CSFA_MASK	(BIT(1) | BIT(0))
+#define AQCSFRC_CSFA_FRCDIS	0
+#define AQCSFRC_CSFA_FRCLOW	BIT(0)
+#define AQCSFRC_CSFA_FRCHIGH	BIT(1)
+#define AQCSFRC_CSFA_DISSWFRC	(BIT(1) | BIT(0))
+
+#define NUM_PWM_CHANNEL		2	/* EHRPWM channels */
+
+struct ehrpwm_pwm_chip {
+	struct pwm_chip	chip;
+	unsigned int	clk_rate;
+	void __iomem	*mmio_base;
+};
+
+static inline struct ehrpwm_pwm_chip *to_ehrpwm_pwm_chip(struct pwm_chip *chip)
+{
+	return container_of(chip, struct ehrpwm_pwm_chip, chip);
+}
+
+static void ehrpwm_write(void *base, int offset, unsigned int val)
+{
+	writew(val & 0xFFFF, base + offset);
+}
+
+static void ehrpwm_modify(void *base, int offset,
+		unsigned short mask, unsigned short val)
+{
+	unsigned short regval;
+
+	regval = readw(base + offset);
+	regval &= ~mask;
+	regval |= val & mask;
+	writew(regval, base + offset);
+}
+
+/**
+ * set_prescale_div -	Set up the prescaler divider function
+ * @rqst_prescaler:	prescaler value min
+ * @prescale_div:	prescaler value set
+ * @tb_clk_div:		Time Base Control prescaler bits
+ */
+static int set_prescale_div(unsigned long rqst_prescaler,
+		unsigned short *prescale_div, unsigned short *tb_clk_div)
+{
+	unsigned int clkdiv, hspclkdiv;
+
+	for (clkdiv = 0; clkdiv <= CLKDIV_MAX; clkdiv++) {
+		for (hspclkdiv = 0; hspclkdiv <= HSPCLKDIV_MAX; hspclkdiv++) {
+
+			/*
+			 * calculations for prescaler value :
+			 * prescale_div = HSPCLKDIVIDER * CLKDIVIDER.
+			 * HSPCLKDIVIDER =  2 ** hspclkdiv
+			 * CLKDIVIDER = (1),		if clkdiv == 0 *OR*
+			 *		(2 * clkdiv),	if clkdiv != 0
+			 *
+			 * Configure prescale_div value such that period
+			 * register value is less than 65535.
+			 */
+
+			*prescale_div = (1 << clkdiv) *
+					(hspclkdiv ? (hspclkdiv * 2) : 1);
+			if (*prescale_div > rqst_prescaler) {
+				*tb_clk_div = (clkdiv << TBCTL_CLKDIV_SHIFT) |
+					(hspclkdiv << TBCTL_HSPCLKDIV_SHIFT);
+				return 0;
+			}
+		}
+	}
+	return 1;
+}
+
+static void configure_chans(struct ehrpwm_pwm_chip *pc, int chan,
+		unsigned long duty_cycles)
+{
+	int cmp_reg, aqctl_reg;
+	unsigned short aqctl_val, aqctl_mask;
+
+	/*
+	 * Channels can be configured from action qualifier module.
+	 * Channel 0 configured with compare A register and for
+	 * up-counter mode.
+	 * Channel 1 configured with compare B register and for
+	 * up-counter mode.
+	 */
+	if (chan == 1) {
+		aqctl_reg = AQCTLB;
+		cmp_reg = CMPB;
+		/* Configure PWM Low from compare B value */
+		aqctl_val = AQCTL_CBU_FRCLOW;
+		aqctl_mask = AQCTL_CBU_MASK;
+	} else {
+		cmp_reg = CMPA;
+		aqctl_reg = AQCTLA;
+		/* Configure PWM Low from compare A value*/
+		aqctl_val = AQCTL_CAU_FRCLOW;
+		aqctl_mask = AQCTL_CAU_MASK;
+	}
+
+	/* Configure PWM High from period value and zero value */
+	aqctl_val |= AQCTL_PRD_FRCHIGH | AQCTL_ZRO_FRCHIGH;
+	aqctl_mask |= AQCTL_PRD_MASK | AQCTL_ZRO_MASK;
+	ehrpwm_modify(pc->mmio_base,  aqctl_reg, aqctl_mask, aqctl_val);
+
+	ehrpwm_write(pc->mmio_base,  cmp_reg, duty_cycles);
+}
+
+/*
+ * period_ns = 10^9 * (ps_divval * period_cycles) / PWM_CLK_RATE
+ * duty_ns   = 10^9 * (ps_divval * duty_cycles) / PWM_CLK_RATE
+ */
+static int ehrpwm_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
+		int duty_ns, int period_ns)
+{
+	struct ehrpwm_pwm_chip *pc = to_ehrpwm_pwm_chip(chip);
+	unsigned long long c;
+	unsigned long period_cycles, duty_cycles;
+	unsigned short ps_divval, tb_divval;
+
+	if (period_ns < 0 || duty_ns < 0 || period_ns > NSEC_PER_SEC)
+		return -ERANGE;
+
+	c = pc->clk_rate;
+	c = c * period_ns;
+	do_div(c, NSEC_PER_SEC);
+	period_cycles = (unsigned long)c;
+
+	if (period_cycles < 1) {
+		period_cycles = 1;
+		duty_cycles = 1;
+	} else {
+		c = pc->clk_rate;
+		c = c * duty_ns;
+		do_div(c, NSEC_PER_SEC);
+		duty_cycles = (unsigned long)c;
+	}
+
+	/* Configure clock prescaler to support Low frequency PWM wave */
+	if (set_prescale_div(period_cycles/PERIOD_MAX, &ps_divval,
+				&tb_divval)) {
+		dev_err(chip->dev, "Unsupported values\n");
+		return -EINVAL;
+	}
+
+	pm_runtime_get_sync(chip->dev);
+
+	/* Update clock prescaler values */
+	ehrpwm_modify(pc->mmio_base, TBCTL, TBCTL_CLKDIV_MASK, tb_divval);
+
+	/* Update period & duty cycle with presacler division */
+	period_cycles = period_cycles / ps_divval;
+	duty_cycles = duty_cycles / ps_divval;
+
+	/* Configure shadow loading on Period register */
+	ehrpwm_modify(pc->mmio_base, TBCTL, TBCTL_PRDLD_MASK, TBCTL_PRDLD_SHDW);
+
+	ehrpwm_write(pc->mmio_base, TBPRD, period_cycles);
+
+	/* Configure ehrpwm counter for up-count mode */
+	ehrpwm_modify(pc->mmio_base, TBCTL, TBCTL_CTRMODE_MASK,
+			TBCTL_CTRMODE_UP);
+
+	/* Configure the channel for duty cycle */
+	configure_chans(pc, pwm->hwpwm, duty_cycles);
+	pm_runtime_put_sync(chip->dev);
+	return 0;
+}
+
+static int ehrpwm_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct ehrpwm_pwm_chip *pc = to_ehrpwm_pwm_chip(chip);
+	unsigned short aqcsfrc_val, aqcsfrc_mask;
+
+	/* Leave clock enabled on enabling PWM */
+	pm_runtime_get_sync(chip->dev);
+
+	/* Disabling Action Qualifier on PWM output */
+	if (pwm->hwpwm) {
+		aqcsfrc_val = AQCSFRC_CSFB_FRCDIS;
+		aqcsfrc_mask = AQCSFRC_CSFB_MASK;
+	} else {
+		aqcsfrc_val = AQCSFRC_CSFA_FRCDIS;
+		aqcsfrc_mask = AQCSFRC_CSFA_MASK;
+	}
+
+	/* Changes to shadow mode */
+	ehrpwm_modify(pc->mmio_base, AQSFRC, AQSFRC_RLDCSF_MASK,
+			AQSFRC_RLDCSF_ZRO);
+
+	ehrpwm_modify(pc->mmio_base, AQCSFRC, aqcsfrc_mask, aqcsfrc_val);
+
+	/* Enable time counter for free_run */
+	ehrpwm_modify(pc->mmio_base, TBCTL, TBCTL_RUN_MASK, TBCTL_FREE_RUN);
+	return 0;
+}
+
+static void ehrpwm_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct ehrpwm_pwm_chip *pc = to_ehrpwm_pwm_chip(chip);
+	unsigned short aqcsfrc_val, aqcsfrc_mask;
+
+	/* Action Qualifier puts PWM output low forcefully */
+	if (pwm->hwpwm) {
+		aqcsfrc_val = AQCSFRC_CSFB_FRCLOW;
+		aqcsfrc_mask = AQCSFRC_CSFB_MASK;
+	} else {
+		aqcsfrc_val = AQCSFRC_CSFA_FRCLOW;
+		aqcsfrc_mask = AQCSFRC_CSFA_MASK;
+	}
+
+	/*
+	 * Changes to immediate action on Action Qualifier. This puts
+	 * Action Qualifier control on PWM output from next TBCLK
+	 */
+	ehrpwm_modify(pc->mmio_base, AQSFRC, AQSFRC_RLDCSF_MASK,
+			AQSFRC_RLDCSF_IMDT);
+
+	ehrpwm_modify(pc->mmio_base, AQCSFRC, aqcsfrc_mask, aqcsfrc_val);
+
+	/* Stop Time base counter */
+	ehrpwm_modify(pc->mmio_base, TBCTL, TBCTL_RUN_MASK, TBCTL_STOP_NEXT);
+
+	/* Disable clock on PWM disable */
+	pm_runtime_put_sync(chip->dev);
+}
+
+static void ehrpwm_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	if (test_bit(PWMF_ENABLED, &pwm->flags)) {
+		dev_warn(chip->dev, "Removing PWM device without disabling\n");
+		pm_runtime_put_sync(chip->dev);
+	}
+}
+
+static const struct pwm_ops ehrpwm_pwm_ops = {
+	.free		= ehrpwm_pwm_free,
+	.config		= ehrpwm_pwm_config,
+	.enable		= ehrpwm_pwm_enable,
+	.disable	= ehrpwm_pwm_disable,
+	.owner		= THIS_MODULE,
+};
+
+static int __devinit ehrpwm_pwm_probe(struct platform_device *pdev)
+{
+	int ret;
+	struct resource *r;
+	struct clk *clk;
+	struct ehrpwm_pwm_chip *pc;
+
+	pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
+	if (!pc) {
+		dev_err(&pdev->dev, "failed to allocate memory\n");
+		return -ENOMEM;
+	}
+
+	clk = devm_clk_get(&pdev->dev, "fck");
+	if (IS_ERR(clk)) {
+		dev_err(&pdev->dev, "failed to get clock\n");
+		return PTR_ERR(clk);
+	}
+
+	pc->clk_rate = clk_get_rate(clk);
+	if (!pc->clk_rate) {
+		dev_err(&pdev->dev, "failed to get clock rate\n");
+		return -EINVAL;
+	}
+
+	pc->chip.dev = &pdev->dev;
+	pc->chip.ops = &ehrpwm_pwm_ops;
+	pc->chip.base = -1;
+	pc->chip.npwm = NUM_PWM_CHANNEL;
+
+	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!r) {
+		dev_err(&pdev->dev, "no memory resource defined\n");
+		return -ENODEV;
+	}
+
+	pc->mmio_base = devm_request_and_ioremap(&pdev->dev, r);
+	if (!pc->mmio_base) {
+		dev_err(&pdev->dev, "failed to ioremap() registers\n");
+		return  -EADDRNOTAVAIL;
+	}
+
+	ret = pwmchip_add(&pc->chip);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
+		return ret;
+	}
+
+	pm_runtime_enable(&pdev->dev);
+	platform_set_drvdata(pdev, pc);
+	return 0;
+}
+
+static int __devexit ehrpwm_pwm_remove(struct platform_device *pdev)
+{
+	struct ehrpwm_pwm_chip *pc = platform_get_drvdata(pdev);
+
+	pm_runtime_put_sync(&pdev->dev);
+	pm_runtime_disable(&pdev->dev);
+	return pwmchip_remove(&pc->chip);
+}
+
+static struct platform_driver ehrpwm_pwm_driver = {
+	.driver = {
+		.name = "ehrpwm",
+	},
+	.probe = ehrpwm_pwm_probe,
+	.remove = __devexit_p(ehrpwm_pwm_remove),
+};
+
+module_platform_driver(ehrpwm_pwm_driver);
+
+MODULE_DESCRIPTION("EHRPWM PWM driver");
+MODULE_AUTHOR("Texas Instruments");
+MODULE_LICENSE("GPL");