Re: [PATCH v3 6/6] ARM: PWM: add allwinner sun8i R40/T3/V40 PWM support.

From: Uwe Kleine-König
Date: Mon Nov 26 2018 - 16:32:12 EST

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In reply to: Hao Zhang: "[PATCH v3 6/6] ARM: PWM: add allwinner sun8i R40/T3/V40 PWM support."
Next in thread: Uwe Kleine-König: "Re: [PATCH v3 6/6] ARM: PWM: add allwinner sun8i R40/T3/V40 PWM support."
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On Mon, Nov 26, 2018 at 12:23:19AM +0800, Hao Zhang wrote:
> The sun8i R40/T3/V40 PWM has 8 PWM channals and divides to 4 PWM pairs,
> each PWM pair built-in 1 clock module, 2 timer logic module and 1
> programmable dead-time generator, it also support waveform capture.
> It has 2 clock sources OSC24M and APB1, it is different with the
> sun4i-pwm driver, Therefore add a new driver for it.
>
> Signed-off-by: Hao Zhang <hao5781286@xxxxxxxxx>
> ---
> drivers/pwm/Kconfig | 12 +-
> drivers/pwm/Makefile | 1 +
> drivers/pwm/pwm-sun8i.c | 418 ++++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 430 insertions(+), 1 deletion(-)
> create mode 100644 drivers/pwm/pwm-sun8i.c
>
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index 504d252..6105ac8 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -426,7 +426,7 @@ config PWM_STMPE
> expanders.
>
> config PWM_SUN4I
> - tristate "Allwinner PWM support"
> + tristate "Allwinner SUN4I PWM support"
> depends on ARCH_SUNXI || COMPILE_TEST
> depends on HAS_IOMEM && COMMON_CLK
> help
> @@ -435,6 +435,16 @@ config PWM_SUN4I
> To compile this driver as a module, choose M here: the module
> will be called pwm-sun4i.
>
> +config PWM_SUN8I
> + tristate "Allwinner SUN8I (R40/V40/T3) PWM support"
> + depends on ARCH_SUNXI || COMPILE_TEST
> + depends on HAS_IOMEM && COMMON_CLK
> + help
> + Generic PWM framework driver for Allwinner R40/V40/T3 SoCs.
> +
> + To compile this driver as a module, choose M here: the module
> + will be called pwm-sun8i.
> +
> config PWM_TEGRA
> tristate "NVIDIA Tegra PWM support"
> depends on ARCH_TEGRA
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index 9c676a0..32c8d2d 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -43,6 +43,7 @@ obj-$(CONFIG_PWM_STM32) += pwm-stm32.o
> obj-$(CONFIG_PWM_STM32_LP) += pwm-stm32-lp.o
> obj-$(CONFIG_PWM_STMPE) += pwm-stmpe.o
> obj-$(CONFIG_PWM_SUN4I) += pwm-sun4i.o
> +obj-$(CONFIG_PWM_SUN8I) += pwm-sun8i.o
> obj-$(CONFIG_PWM_TEGRA) += pwm-tegra.o
> obj-$(CONFIG_PWM_TIECAP) += pwm-tiecap.o
> obj-$(CONFIG_PWM_TIEHRPWM) += pwm-tiehrpwm.o
> diff --git a/drivers/pwm/pwm-sun8i.c b/drivers/pwm/pwm-sun8i.c
> new file mode 100644
> index 0000000..d8597e4
> --- /dev/null
> +++ b/drivers/pwm/pwm-sun8i.c
> @@ -0,0 +1,418 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (C) 2018 Hao Zhang <hao5781286@xxxxxxxxx>
> +
> +#include <linux/bitops.h>
> +#include <linux/clk.h>
> +#include <linux/clk-provider.h>
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>
> +#include <linux/time.h>
> +#include <linux/regmap.h>
> +
> +#define PWM_IRQ_ENABLE_REG 0x0000
> +#define PCIE(ch) BIT(ch)
> +
> +#define PWM_IRQ_STATUS_REG 0x0004
> +#define PIS(ch) BIT(ch)
> +
> +#define CAPTURE_IRQ_ENABLE_REG 0x0010
> +#define CRIE(ch) BIT((ch) * 2)
> +#define CFIE(ch) BIT((ch) * 2 + 1)
> +
> +#define CAPTURE_IRQ_STATUS_REG 0x0014
> +#define CRIS(ch) BIT((ch) * 2)
> +#define CFIS(ch) BIT((ch) * 2 + 1)
> +
> +#define CLK_CFG_REG(ch) (0x0020 + ((ch) >> 1) * 4)
> +#define CLK_SRC_SEL GENMASK(8, 7)
> +#define CLK_SRC_BYPASS_SEC BIT(6)
> +#define CLK_SRC_BYPASS_FIR BIT(5)
> +#define CLK_GATING BIT(4)
> +#define CLK_DIV_M GENMASK(3, 0)
> +
> +#define PWM_DZ_CTR_REG(ch) (0x0030 + ((ch) >> 1) * 4)
> +#define PWM_DZ_INTV GENMASK(15, 8)
> +#define PWM_DZ_EN BIT(0)
> +
> +#define PWM_ENABLE_REG 0x0040
> +#define PWM_EN(ch) BIT(ch)
> +
> +#define CAPTURE_ENABLE_REG 0x0044
> +#define CAP_EN(ch) BIT(ch)
> +
> +#define PWM_CTR_REG(ch) (0x0060 + (ch) * 0x20)
> +#define PWM_PERIOD_RDY BIT(11)
> +#define PWM_PUL_START BIT(10)
> +#define PWM_MODE BIT(9)
> +#define PWM_ACT_STA BIT(8)
> +#define PWM_PRESCAL_K GENMASK(7, 0)
> +
> +#define PWM_PERIOD_REG(ch) (0x0064 + (ch) * 0x20)
> +#define PWM_ENTIRE_CYCLE GENMASK(31, 16)
> +#define PWM_ACT_CYCLE GENMASK(15, 0)
> +
> +#define PWM_CNT_REG(ch) (0x0068 + (ch) * 0x20)
> +#define PWM_CNT_VAL GENMASK(15, 0)
> +
> +#define CAPTURE_CTR_REG(ch) (0x006c + (ch) * 0x20)
> +#define CAPTURE_CRLF BIT(2)
> +#define CAPTURE_CFLF BIT(1)
> +#define CAPINV BIT(0)
> +
> +#define CAPTURE_RISE_REG(ch) (0x0070 + (ch) * 0x20)
> +#define CAPTURE_CRLR GENMASK(15, 0)
> +
> +#define CAPTURE_FALL_REG(ch) (0x0074 + (ch) * 0x20)
> +#define CAPTURE_CFLR GENMASK(15, 0)
> +
> +struct sun8i_pwm_chip {
> + struct pwm_chip chip;
> + struct clk *clk;
> + void __iomem *base;
> + const struct sun8i_pwm_data *data;

This member is only written to, but never used.

> + struct regmap *regmap;
> +};
> +
> +static struct sun8i_pwm_chip *to_sun8i_pwm_chip(struct pwm_chip *chip)
> +{
> + return container_of(chip, struct sun8i_pwm_chip, chip);
> +}
> +
> +static u32 sun8i_pwm_read(struct sun8i_pwm_chip *sun8i_pwm,
> + unsigned long offset)
> +{
> + u32 val;
> +
> + regmap_read(sun8i_pwm->regmap, offset, &val);
> + return val;
> +}
> +
> +static void sun8i_pwm_set_bit(struct sun8i_pwm_chip *sun8i_pwm,
> + unsigned long reg, u32 bit)
> +{
> + regmap_update_bits(sun8i_pwm->regmap, reg, bit, bit);
> +}
> +
> +static void sun8i_pwm_clear_bit(struct sun8i_pwm_chip *sun8i_pwm,
> + unsigned long reg, u32 bit)
> +{
> + regmap_update_bits(sun8i_pwm->regmap, reg, bit, 0);
> +}
> +
> +static void sun8i_pwm_set_value(struct sun8i_pwm_chip *sun8i_pwm,
> + unsigned long reg, u32 mask, u32 val)
> +{
> + regmap_update_bits(sun8i_pwm->regmap, reg, mask, val);
> +}
> +
> +static void sun8i_pwm_set_polarity(struct sun8i_pwm_chip *chip, u32 ch,
> + enum pwm_polarity polarity)
> +{
> + if (polarity == PWM_POLARITY_NORMAL)
> + sun8i_pwm_set_bit(chip, PWM_CTR_REG(ch), PWM_ACT_STA);
> + else
> + sun8i_pwm_clear_bit(chip, PWM_CTR_REG(ch), PWM_ACT_STA);
> +}

This function is only used once. Maybe drop the function and put the if
to the caller.

> +
> +static int sun8i_pwm_config(struct sun8i_pwm_chip *sun8i_pwm, u8 ch,
> + struct pwm_state *state)
> +{
> + u64 clk_rate, clk_div, val;
> + u16 prescaler = 0;
> + u16 div_id = 0;
> + struct clk *clk;
> + bool is_clk;
> + int ret;
> +
> + clk_rate = clk_get_rate(sun8i_pwm->clk);
> +
> + /* check period and select clock source */
> + val = state->period * clk_rate;
> + do_div(val, NSEC_PER_SEC);
> + is_clk = devm_clk_name_match(sun8i_pwm->clk, "mux-0");
> + if (val <= 1 && is_clk) {
> + clk = devm_clk_get(sun8i_pwm->chip.dev, "mux-1");
> + if (IS_ERR(clk)) {
> + dev_err(sun8i_pwm->chip.dev,
> + "Period expects a larger value\n");

This error message looks wrong, several others, too.

> + return -EINVAL;

return PTR_ERR(clk)?

> + }
> +
> + clk_rate = clk_get_rate(clk);
> + val = state->period * clk_rate;
> + do_div(val, NSEC_PER_SEC);
> + if (val <= 1) {
> + dev_err(sun8i_pwm->chip.dev,
> + "Period expects a larger value\n");
> + return -EINVAL;
> + }
> +
> + /* change clock source to "mux-1" */
> + clk_disable_unprepare(sun8i_pwm->clk);
> + devm_clk_put(sun8i_pwm->chip.dev, sun8i_pwm->clk);
> + sun8i_pwm->clk = clk;

sun8i_pwm is shared for all 8 PWMs, right? So if you assign mux-1 here
for the second mux, how does this influence the first PWM?

mux-0 might already be enabled, it is then never disabled.

> +
> + ret = clk_prepare_enable(sun8i_pwm->clk);
> + if (ret) {
> + dev_err(sun8i_pwm->chip.dev,
> + "Failed to enable PWM clock\n");
> + return ret;
> + }
> +
> + } else {
> + dev_err(sun8i_pwm->chip.dev,
> + "Period expects a larger value\n");
> + return -EINVAL;

This looks wrong. If val is > 1 there shouldn't be a reason to abort?

> + }
> +
> + is_clk = devm_clk_name_match(sun8i_pwm->clk, "mux-0");
> + if (is_clk)
> + sun8i_pwm_set_value(sun8i_pwm, CLK_CFG_REG(ch),
> + CLK_SRC_SEL, 0 << 7);
> + else
> + sun8i_pwm_set_value(sun8i_pwm, CLK_CFG_REG(ch),
> + CLK_SRC_SEL, 1 << 7);
> +
> + dev_info(sun8i_pwm->chip.dev, "clock source freq:%lldHz\n", clk_rate);

I'd degrade this to dev_dbg.

> +
> + /* calculate and set prescaler, div table, PWM entire cycle */
> + clk_div = val;
> + while (clk_div > 65535) {
> + prescaler++;
> + clk_div = val;
> + do_div(clk_div, 1U << div_id);
> + do_div(clk_div, prescaler + 1);
> +
> + if (prescaler == 255) {
> + prescaler = 0;
> + div_id++;
> + if (div_id == 9) {
> + dev_err(sun8i_pwm->chip.dev,
> + "unsupport period value\n");
> + return -EINVAL;
> + }
> + }
> + }

Noting the underlying formula for the calculation and the bitwidth for
the related register fields above would be good.

> +
> + sun8i_pwm_set_value(sun8i_pwm, PWM_PERIOD_REG(ch),
> + PWM_ENTIRE_CYCLE, clk_div << 16);
> + sun8i_pwm_set_value(sun8i_pwm, PWM_CTR_REG(ch),
> + PWM_PRESCAL_K, prescaler << 0);
> + sun8i_pwm_set_value(sun8i_pwm, CLK_CFG_REG(ch),
> + CLK_DIV_M, div_id << 0);
> +
> + /* set duty cycle */
> + val = state->period;
> + do_div(val, clk_div);
> + clk_div = state->duty_cycle;
> + do_div(clk_div, val);
> + if (clk_div > 65535)
> + clk_div = 65535;
> +
> + sun8i_pwm_set_value(sun8i_pwm, PWM_PERIOD_REG(ch),
> + PWM_ACT_CYCLE, clk_div << 0);

Why "<< 0"?

> + return 0;
> +}
> +
> +static int sun8i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> + struct pwm_state *state)
> +{
> + int ret;
> + struct sun8i_pwm_chip *sun8i_pwm = to_sun8i_pwm_chip(chip);
> + struct pwm_state cstate;
> +
> + pwm_get_state(pwm, &cstate);
> + if (!cstate.enabled) {
> + ret = clk_prepare_enable(sun8i_pwm->clk);
> + if (ret) {
> + dev_err(chip->dev, "Failed to enable PWM clock\n");
> + return ret;
> + }
> + }
> +
> + if ((cstate.period != state->period) ||
> + (cstate.duty_cycle != state->duty_cycle)) {
> + ret = sun8i_pwm_config(sun8i_pwm, pwm->hwpwm, state);
> + if (ret) {
> + dev_err(chip->dev, "Failed to config PWM\n");
> + return ret;
> + }
> + }

sun8i_pwm_config writes the registers that are relevant for period and
duty_cycle. When do these values take effect? If it's already here,
switching the polarity below might introduce a glitch.

> + if (state->polarity != cstate.polarity)
> + sun8i_pwm_set_polarity(sun8i_pwm, pwm->hwpwm, state->polarity);
> +
> + if (state->enabled) {
> + sun8i_pwm_set_bit(sun8i_pwm,
> + CLK_CFG_REG(pwm->hwpwm), CLK_GATING);
> +
> + sun8i_pwm_set_bit(sun8i_pwm,
> + PWM_ENABLE_REG, PWM_EN(pwm->hwpwm));
> + } else {
> + sun8i_pwm_clear_bit(sun8i_pwm,
> + CLK_CFG_REG(pwm->hwpwm), CLK_GATING);
> +
> + sun8i_pwm_clear_bit(sun8i_pwm,
> + PWM_ENABLE_REG, PWM_EN(pwm->hwpwm));
> + }

Please document how the hardware behaves when being disabled. (Does it
drive a 0? Does it drive a 1 when inverted? Or is the output high-z?)

> +
> + return 0;
> +}
> +
> +static void sun8i_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> + struct pwm_state *state)
> +{
> + struct sun8i_pwm_chip *sun8i_pwm = to_sun8i_pwm_chip(chip);
> + u64 clk_rate, tmp;
> + u32 val;
> + u16 clk_div, act_cycle;
> + u8 prescal, div_id;
> + u8 chn = pwm->hwpwm;
> +
> + clk_rate = clk_get_rate(sun8i_pwm->clk);
> +
> + val = sun8i_pwm_read(sun8i_pwm, PWM_CTR_REG(chn));
> + if (PWM_ACT_STA & val)

This looks strange to me. While syntactically equivalent it is more
usual to write this as

if (val & PWM_ACT_STA)

> + state->polarity = PWM_POLARITY_NORMAL;
> + else
> + state->polarity = PWM_POLARITY_INVERSED;
> +
> + prescal = PWM_PRESCAL_K & val;
> +
> + val = sun8i_pwm_read(sun8i_pwm, PWM_ENABLE_REG);
> + if (PWM_EN(chn) & val)
> + state->enabled = true;
> + else
> + state->enabled = false;

When the PWM should be enabled, you also set the CLK_GATING bit. Should
this better be checked for in .get_state, too?

> +
> + val = sun8i_pwm_read(sun8i_pwm, PWM_PERIOD_REG(chn));
> + act_cycle = PWM_ACT_CYCLE & val;
> + clk_div = val >> 16;
> +
> + val = sun8i_pwm_read(sun8i_pwm, CLK_CFG_REG(chn));
> + div_id = CLK_DIV_M & val;
> +
> + tmp = act_cycle * prescal * (1U << div_id) * NSEC_PER_SEC;
> + state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, clk_rate);
> + tmp = clk_div * prescal * (1U << div_id) * NSEC_PER_SEC;
> + state->period = DIV_ROUND_CLOSEST_ULL(tmp, clk_rate);
> +}
> +
> +static const struct regmap_config sun8i_pwm_regmap_config = {
> + .reg_bits = 32,
> + .reg_stride = 4,
> + .val_bits = 32,
> + .max_register = CAPTURE_FALL_REG(7),
> +};
> +
> +static const struct pwm_ops sun8i_pwm_ops = {
> + .apply = sun8i_pwm_apply,
> + .get_state = sun8i_pwm_get_state,
> + .owner = THIS_MODULE,
> +};
> +
> +static const struct of_device_id sun8i_pwm_dt_ids[] = {
> + {
> + .compatible = "allwinner,sun8i-r40-pwm",
> + .data = NULL,

.data doesn't need to be specified.

> + },
> + {},
> +};
> +MODULE_DEVICE_TABLE(of, sun8i_pwm_dt_ids);
> +
> +static int sun8i_pwm_probe(struct platform_device *pdev)
> +{
> + struct device_node *np = pdev->dev.of_node;
> + struct sun8i_pwm_chip *pwm;
> + struct resource *res;
> + int ret;
> + const struct of_device_id *match;
> +
> + match = of_match_device(sun8i_pwm_dt_ids, &pdev->dev);
> + if (!match) {
> + dev_err(&pdev->dev, "Error: No device match found\n");
> + return -ENODEV;
> + }

This prevents a match by driver-name, right? Other than that match is
only used to assign pwm->data below to NULL.

> +
> + pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
> + if (!pwm)
> + return -ENOMEM;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + pwm->base = devm_ioremap_resource(&pdev->dev, res);
> + if (IS_ERR(pwm->base))
> + return PTR_ERR(pwm->base);
> +
> + pwm->regmap = devm_regmap_init_mmio(&pdev->dev, pwm->base,
> + &sun8i_pwm_regmap_config);
> + if (IS_ERR(pwm->regmap)) {
> + dev_err(&pdev->dev, "Failed to create regmap\n");
> + return PTR_ERR(pwm->regmap);
> + }
> +
> + /* we use mux-0 as default clock source */
> + pwm->clk = devm_clk_get(&pdev->dev, "mux-0");
> + if (IS_ERR(pwm->clk)) {

You might want to handle pwm->clk == ERR_PTR(-EPROBE_DEFER) without falling
back to mux-1 and without printing an error.

> + pwm->clk = devm_clk_get(&pdev->dev, "mux-1");
> + if (IS_ERR(pwm->clk)) {
> + dev_err(&pdev->dev, "Failed to get PWM clock\n");
> + return PTR_ERR(pwm->clk);
> + }
> + }
> +
> + ret = of_property_read_u32(np, "pwm-channels", &pwm->chip.npwm);
> + if (ret && !pwm->chip.npwm) {

This is equivalent to

if (ret)

because &pwm->chip.npwm is only modified if of_property_read_u32
returns 0 and the variable holds a 0 before.

> + dev_err(&pdev->dev, "Can't get pwm-channels\n");
> + return ret;
> + }
> +
> + dev_info(&pdev->dev, "pwm-channels:%d\n", pwm->chip.npwm);

dev_dbg?

> + pwm->data = match->data;
> + pwm->chip.dev = &pdev->dev;
> + pwm->chip.ops = &sun8i_pwm_ops;
> + pwm->chip.base = -1;
> + pwm->chip.of_xlate = of_pwm_xlate_with_flags;
> + pwm->chip.of_pwm_n_cells = 3;
> +
> + ret = pwmchip_add(&pwm->chip);
> + if (ret < 0) {
> + dev_err(&pdev->dev, "Failed to add PWM chip: %d\n", ret);
> + return ret;
> + }
> +
> + platform_set_drvdata(pdev, pwm);

If you do this earlier (typically after the allocation succeeded) you
can simplify the last few lines to:

ret = pwmchip_add(&pwm->chip);
if (ret < 0)
dev_err(&pdev->dev, ...);

return ret;

> +static int sun8i_pwm_remove(struct platform_device *pdev)
> +{
> + struct sun8i_pwm_chip *pwm = platform_get_drvdata(pdev);
> +
> + clk_disable_unprepare(pwm->clk);
> + return pwmchip_remove(&pwm->chip);

This is at least unusual (and maybe broken). Please call pwmchip_remove
before clk_disable_unprepare.

> +}
> +
> +static struct platform_driver sun8i_pwm_driver = {
> + .driver = {
> + .name = "sun8i-pwm",
> + .of_match_table = sun8i_pwm_dt_ids,
> + },
> + .probe = sun8i_pwm_probe,
> + .remove = sun8i_pwm_remove,
> +};
> +module_platform_driver(sun8i_pwm_driver);
> +
> +MODULE_ALIAS("platform: sun8i-pwm");

I think the space in the alias must be dropped. Giving that the driver
doesn't bind by driver-name I suggest to drop this completely.

> +MODULE_AUTHOR("Hao Zhang <hao5781286@xxxxxxxxx>");
> +MODULE_DESCRIPTION("Allwinner sun8i PWM driver");
> +MODULE_LICENSE("GPL v2");

Best regards
Uwe

--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |

Next message: Boris Brezillon: "Re: [PATCH] i3c: master: dw: split dw-i3c-master.c into master and bus specific parts"
Previous message: Steven Rostedt: "Re: [RFC][PATCH 11/14] function_graph: Convert ret_stack to a series of longs"
In reply to: Hao Zhang: "[PATCH v3 6/6] ARM: PWM: add allwinner sun8i R40/T3/V40 PWM support."
Next in thread: Uwe Kleine-König: "Re: [PATCH v3 6/6] ARM: PWM: add allwinner sun8i R40/T3/V40 PWM support."
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