[PATCH v6 2/4] pwm: driver for qualcomm ipq6018 pwm block

Baruch Siach
2021-07-22T10:11:25Z

Driver for the PWM block in Qualcomm IPQ6018 line of SoCs. Based on
driver from downstream Codeaurora kernel tree. Removed support for older
(V1) variants because I have no access to that hardware.

Tested on IPQ6010 based hardware.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
---
v6:

Address Uwe Kleine-König review comments:

Drop IPQ_PWM_MAX_DEVICES

Rely on assigned-clock-rates; drop IPQ_PWM_CLK_SRC_FREQ

Simplify register offset calculation

Calculate duty cycle more precisely

Refuse to set inverted polarity

Drop redundant IPQ_PWM_REG1_ENABLE bit clear

Remove x1000 factor in pwm_div calculation, use rate directly, and round up

Choose initial pre_div such that pwm_div < IPQ_PWM_MAX_DIV

Ensure pre_div <= pwm_div

Rename close_ to best_

Explain in comment why effective_div doesn't overflow

Limit pwm_div to IPQ_PWM_MAX_DIV - 1 to allow 100% duty cycle

Disable clock only after pwmchip_remove()

const pwm_ops

Other changes:

Add missing linux/bitfield.h header include (kernel test robot)

Adjust code for PWM device node under TCSR (Rob Herring)

v5:

Use &tcsr_q6 syscon to access registers (Bjorn Andersson)

Address Uwe Kleine-König review comments:

Implement .get_state()

Add IPQ_PWM_ prefix to local macros

Use GENMASK/BIT/FIELD_PREP for register fields access

Make type of config_div_and_duty() parameters consistent

Derive IPQ_PWM_MIN_PERIOD_NS from IPQ_PWM_CLK_SRC_FREQ

Integrate enable/disable into config_div_and_duty() to save register read,
and reduce frequency glitch on update

Use min() instead of min_t()

Fix comment format

Use dev_err_probe() to indicate probe step failure

Add missing clk_disable_unprepare() in .remove

Don't set .owner

v4:

Use div64_u64() to fix link for 32-bit targets ((kernel test robot
<lkp@intel.com>, Uwe Kleine-König)

v3:

s/qcom,pwm-ipq6018/qcom,ipq6018-pwm/ (Rob Herring)

Fix integer overflow on 32-bit targets (kernel test robot <lkp@intel.com>)

v2:

Address Uwe Kleine-König review comments:

Fix period calculation when out of range

Don't set period larger than requested

Remove PWM disable on configuration change

Implement .apply instead of non-atomic .config/.enable/.disable

Don't modify PWM on .request/.free

Check pwm_div underflow

Fix various code and comment formatting issues

Other changes:

Use u64 divisor safe division

Remove now empty .request/.free
---
drivers/pwm/Kconfig | 12 ++
drivers/pwm/Makefile | 1 +
drivers/pwm/pwm-ipq.c | 276 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 289 insertions(+)
create mode 100644 drivers/pwm/pwm-ipq.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index c76adedd58c9..08add845596f 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -260,6 +260,18 @@ config PWM_INTEL_LGM
To compile this driver as a module, choose M here: the module
will be called pwm-intel-lgm.

+config PWM_IPQ
+ tristate "IPQ PWM support"
+ depends on ARCH_QCOM || COMPILE_TEST
+ depends on HAVE_CLK && HAS_IOMEM
+ help
+ Generic PWM framework driver for IPQ PWM block which supports
+ 4 pwm channels. Each of the these channels can be configured
+ independent of each other.
+
+ To compile this driver as a module, choose M here: the module
+ will be called pwm-ipq.
+
config PWM_IQS620A
tristate "Azoteq IQS620A PWM support"
depends on MFD_IQS62X || COMPILE_TEST
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 708840b7fba8..7402feae4b36 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -22,6 +22,7 @@ obj-$(CONFIG_PWM_IMX1) += pwm-imx1.o
obj-$(CONFIG_PWM_IMX27) += pwm-imx27.o
obj-$(CONFIG_PWM_IMX_TPM) += pwm-imx-tpm.o
obj-$(CONFIG_PWM_INTEL_LGM) += pwm-intel-lgm.o
+obj-$(CONFIG_PWM_IPQ) += pwm-ipq.o
obj-$(CONFIG_PWM_IQS620A) += pwm-iqs620a.o
obj-$(CONFIG_PWM_JZ4740) += pwm-jz4740.o
obj-$(CONFIG_PWM_KEEMBAY) += pwm-keembay.o
diff --git a/drivers/pwm/pwm-ipq.c b/drivers/pwm/pwm-ipq.c
new file mode 100644
index 000000000000..19f7ed93dc81
--- /dev/null
+++ b/drivers/pwm/pwm-ipq.c
@@ -0,0 +1,276 @@
+// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
+/*
+ * Copyright (c) 2016-2017, 2020 The Linux Foundation. All rights reserved.
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/math64.h>
+#include <linux/of_device.h>
+#include <linux/mfd/syscon.h>
+#include <linux/regmap.h>
+#include <linux/bitfield.h>
+
+/* The frequency range supported is 1 Hz to clock rate */
+#define IPQ_PWM_MAX_PERIOD_NS ((u64)NSEC_PER_SEC)
+
+/*
+ * The max value specified for each field is based on the number of bits
+ * in the pwm control register for that field
+ */
+#define IPQ_PWM_MAX_DIV 0xFFFF
+
+/*
+ * Two 32-bit registers for each PWM: REG0, and REG1.
+ * Base offset for PWM #i is at 8 * #i.
+ */
+#define IPQ_PWM_CFG_REG0 0 /*PWM_DIV PWM_HI*/
+#define IPQ_PWM_REG0_PWM_DIV GENMASK(15, 0)
+#define IPQ_PWM_REG0_HI_DURATION GENMASK(31, 16)
+
+#define IPQ_PWM_CFG_REG1 4 /*ENABLE UPDATE PWM_PRE_DIV*/
+#define IPQ_PWM_REG1_PRE_DIV GENMASK(15, 0)
+/*
+ * Enable bit is set to enable output toggling in pwm device.
+ * Update bit is set to reflect the changed divider and high duration
+ * values in register.
+ */
+#define IPQ_PWM_REG1_UPDATE BIT(30)
+#define IPQ_PWM_REG1_ENABLE BIT(31)
+
+
+struct ipq_pwm_chip {
+ struct pwm_chip chip;
+ struct clk *clk;
+ struct regmap *regmap;
+ u32 regmap_off;
+};
+
+static struct ipq_pwm_chip *to_ipq_pwm_chip(struct pwm_chip *chip)
+{
+ return container_of(chip, struct ipq_pwm_chip, chip);
+}
+
+static unsigned int ipq_pwm_reg_read(struct pwm_device *pwm, unsigned reg)
+{
+ struct ipq_pwm_chip *ipq_chip = to_ipq_pwm_chip(pwm->chip);
+ unsigned int off = ipq_chip->regmap_off + 8 * pwm->hwpwm + reg;
+ unsigned int val;
+
+ regmap_read(ipq_chip->regmap, off, &val);
+
+ return val;
+}
+
+static void ipq_pwm_reg_write(struct pwm_device *pwm, unsigned reg,
+ unsigned val)
+{
+ struct ipq_pwm_chip *ipq_chip = to_ipq_pwm_chip(pwm->chip);
+ unsigned int off = ipq_chip->regmap_off + 8 * pwm->hwpwm + reg;
+
+ regmap_write(ipq_chip->regmap, off, val);
+}
+
+static void config_div_and_duty(struct pwm_device *pwm, unsigned int pre_div,
+ unsigned int pwm_div, unsigned long rate, u64 duty_ns,
+ bool enable)
+{
+ unsigned long hi_dur;
+ unsigned long val = 0;
+
+ /*
+ * high duration = pwm duty * (pwm div + 1)
+ * pwm duty = duty_ns / period_ns
+ */
+ hi_dur = div64_u64(duty_ns * rate, (pre_div + 1) * NSEC_PER_SEC);
+
+ val = FIELD_PREP(IPQ_PWM_REG0_HI_DURATION, hi_dur) |
+ FIELD_PREP(IPQ_PWM_REG0_PWM_DIV, pwm_div);
+ ipq_pwm_reg_write(pwm, IPQ_PWM_CFG_REG0, val);
+
+ val = FIELD_PREP(IPQ_PWM_REG1_PRE_DIV, pre_div);
+ ipq_pwm_reg_write(pwm, IPQ_PWM_CFG_REG1, val);
+
+ /* Enable needs a separate write to REG1 */
+ val |= IPQ_PWM_REG1_UPDATE;
+ if (enable)
+ val |= IPQ_PWM_REG1_ENABLE;
+ ipq_pwm_reg_write(pwm, IPQ_PWM_CFG_REG1, val);
+}
+
+static int ipq_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+ const struct pwm_state *state)
+{
+ struct ipq_pwm_chip *ipq_chip = to_ipq_pwm_chip(chip);
+ unsigned long freq;
+ unsigned int pre_div, pwm_div, best_pre_div, best_pwm_div;
+ long long diff;
+ unsigned long rate = clk_get_rate(ipq_chip->clk);
+ unsigned long min_diff = rate;
+ u64 period_ns, duty_ns;
+
+ if (state->polarity != PWM_POLARITY_NORMAL)
+ return -EINVAL;
+
+ if (state->period < div64_u64(NSEC_PER_SEC, rate))
+ return -ERANGE;
+
+ period_ns = min(state->period, IPQ_PWM_MAX_PERIOD_NS);
+ duty_ns = min(state->duty_cycle, period_ns);
+
+ /* freq in Hz for period in nano second */
+ freq = div64_u64(NSEC_PER_SEC, period_ns);
+ best_pre_div = IPQ_PWM_MAX_DIV;
+ best_pwm_div = IPQ_PWM_MAX_DIV;
+ /* Initial pre_div value such that pwm_div < IPQ_PWM_MAX_DIV */
+ pre_div = DIV64_U64_ROUND_UP(period_ns * rate,
+ (u64)NSEC_PER_SEC * (IPQ_PWM_MAX_DIV + 1));
+
+ for (; pre_div <= IPQ_PWM_MAX_DIV; pre_div++) {
+ pwm_div = DIV64_U64_ROUND_UP(period_ns * rate,
+ (u64)NSEC_PER_SEC * (pre_div + 1));
+ pwm_div--;
+
+ if (pre_div > pwm_div)
+ break;
+
+ /*
+ * Make sure we can do 100% duty cycle where
+ * hi_dur == pwm_div + 1
+ */
+ if (pwm_div > IPQ_PWM_MAX_DIV - 1)
+ continue;
+
+ diff = ((uint64_t)freq * (pre_div + 1) * (pwm_div + 1))
+ - (uint64_t)rate;
+
+ if (diff < 0) /* period larger than requested */
+ continue;
+ if (diff == 0) { /* bingo */
+ best_pre_div = pre_div;
+ best_pwm_div = pwm_div;
+ break;
+ }
+ if (diff < min_diff) {
+ min_diff = diff;
+ best_pre_div = pre_div;
+ best_pwm_div = pwm_div;
+ }
+ }
+
+ /* config divider values for the closest possible frequency */
+ config_div_and_duty(pwm, best_pre_div, best_pwm_div,
+ rate, duty_ns, state->enabled);
+
+ return 0;
+}
+
+static void ipq_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+ struct pwm_state *state)
+{
+ struct ipq_pwm_chip *ipq_chip = to_ipq_pwm_chip(chip);
+ unsigned long rate = clk_get_rate(ipq_chip->clk);
+ unsigned int pre_div, pwm_div, hi_dur;
+ u64 effective_div, hi_div;
+ u32 reg0, reg1;
+
+ reg0 = ipq_pwm_reg_read(pwm, IPQ_PWM_CFG_REG0);
+ reg1 = ipq_pwm_reg_read(pwm, IPQ_PWM_CFG_REG1);
+
+ state->polarity = PWM_POLARITY_NORMAL;
+ state->enabled = reg1 & IPQ_PWM_REG1_ENABLE;
+
+ pwm_div = FIELD_GET(IPQ_PWM_REG0_PWM_DIV, reg0);
+ hi_dur = FIELD_GET(IPQ_PWM_REG0_HI_DURATION, reg0);
+ pre_div = FIELD_GET(IPQ_PWM_REG1_PRE_DIV, reg1);
+
+ /* No overflow here, both pre_div and pwm_div <= 0xffff */
+ effective_div = (u64)(pre_div + 1) * (pwm_div + 1);
+ state->period = div64_u64(effective_div * NSEC_PER_SEC, rate);
+
+ hi_div = hi_dur * (pre_div + 1);
+ state->duty_cycle = div64_u64(hi_div * NSEC_PER_SEC, rate);
+}
+
+static const struct pwm_ops ipq_pwm_ops = {
+ .apply = ipq_pwm_apply,
+ .get_state = ipq_pwm_get_state,
+ .owner = THIS_MODULE,
+};
+
+static int ipq_pwm_probe(struct platform_device *pdev)
+{
+ struct ipq_pwm_chip *pwm;
+ struct device *dev = &pdev->dev;
+ int ret;
+
+ pwm = devm_kzalloc(dev, sizeof(*pwm), GFP_KERNEL);
+ if (!pwm)
+ return -ENOMEM;
+
+ platform_set_drvdata(pdev, pwm);
+
+ pwm->regmap = syscon_node_to_regmap(dev->parent->of_node);
+ if (IS_ERR(pwm->regmap))
+ return dev_err_probe(dev, PTR_ERR(pwm->regmap),
+ "regs map failed");
+
+ ret = of_property_read_u32(dev->of_node, "offset", &pwm->regmap_off);
+ if (ret)
+ return dev_err_probe(dev, ret, "error reading 'offset'");
+
+ pwm->clk = devm_clk_get(dev, "core");
+ if (IS_ERR(pwm->clk))
+ return dev_err_probe(dev, PTR_ERR(pwm->clk),
+ "failed to get core clock");
+
+ ret = clk_prepare_enable(pwm->clk);
+ if (ret)
+ return dev_err_probe(dev, ret, "clock enable failed");
+
+ pwm->chip.dev = dev;
+ pwm->chip.ops = &ipq_pwm_ops;
+ pwm->chip.npwm = 4;
+
+ ret = pwmchip_add(&pwm->chip);
+ if (ret < 0) {
+ dev_err_probe(dev, ret, "pwmchip_add() failed\n");
+ clk_disable_unprepare(pwm->clk);
+ return ret;
+ }
+
+ return 0;
+}
+
+static int ipq_pwm_remove(struct platform_device *pdev)
+{
+ struct ipq_pwm_chip *pwm = platform_get_drvdata(pdev);
+
+ pwmchip_remove(&pwm->chip);
+ clk_disable_unprepare(pwm->clk);
+
+ return 0;
+}
+
+static const struct of_device_id pwm_ipq_dt_match[] = {
+ { .compatible = "qcom,ipq6018-pwm", },
+ {}
+};
+MODULE_DEVICE_TABLE(of, pwm_ipq_dt_match);
+
+static struct platform_driver ipq_pwm_driver = {
+ .driver = {
+ .name = "ipq-pwm",
+ .of_match_table = pwm_ipq_dt_match,
+ },
+ .probe = ipq_pwm_probe,
+ .remove = ipq_pwm_remove,
+};
+
+module_platform_driver(ipq_pwm_driver);
+
+MODULE_LICENSE("Dual BSD/GPL");
--
2.30.2