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Date: Tue, 12 Mar 2019 13:42:57 +0800
From: Hao Zhang <hao5781286@...il.com>
To: Thierry Reding <thierry.reding@...il.com>
Cc: robh+dt@...nel.org, Mark Rutland <mark.rutland@....com>,
Maxime Ripard <maxime.ripard@...tlin.com>,
Chen-Yu Tsai <wens@...e.org>,
Michael Turquette <mturquette@...libre.com>, sboyd@...nel.org,
linux-gpio@...r.kernel.org,
open list <linux-kernel@...r.kernel.org>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@...r.kernel.org>,
"moderated list:ARM/Allwinner sunXi SoC support"
<linux-arm-kernel@...ts.infradead.org>, linux-pwm@...r.kernel.org,
linux-sunxi@...glegroups.com
Subject: Re: [PATCH v3 6/6] ARM: PWM: add allwinner sun8i R40/T3/V40 PWM support.
Thierry Reding <thierry.reding@...il.com> 于2018年12月21日周五 上午1:57写道：
>
> 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@...il.com>
> > ---
> > 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@...il.com>
> > +
> > +#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;
> > + 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);
> > +}
> > +
> > +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");
> > + return -EINVAL;
> > + }
>
> You should never try to get resources at this point. You should have
> requested them already at ->probe() time. Otherwise, how are you going
> to handle failures here?
>
Something wrong here, i will fix it, thanks :)
> > +
> > + 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;
> > +
> > + 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;
> > + }
> > +
> > + 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);
> > +
> > + /* 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;
> > + }
> > + }
> > + }
> > +
> > + 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);
> > +
> > + 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;
> > + }
> > + }
>
> So this isn't really how atomic is supposed to work. The whole point of
> the single callback is to allow the driver to apply the changes in an
> atomic way, which means that either everything is applied or nothing is
> applied.
>
> That's not what you do here. In the above you can end up with an enabled
> clock but the settings not being applied. Similarly sun8i_pwm_config()
> can abort in a number of places, which would leave you with a half-
> configured PWM channel.
>
> Instead, what you should be doing is precompute everything and check
> that the configuration can be applied before touching any registers or
> enabling clocks. Once you've validate the new state, you need to write
> everything and there should be no more risk of failure.
>
Got it, it is useful for me !
> Thierry
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