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Date: Thu, 9 May 2019 09:20:18 +0200
From: Uwe Kleine-König
<u.kleine-koenig@...gutronix.de>
To: Anson Huang <anson.huang@....com>
Cc: "thierry.reding@...il.com" <thierry.reding@...il.com>,
"robh+dt@...nel.org" <robh+dt@...nel.org>,
"mark.rutland@....com" <mark.rutland@....com>,
"shawnguo@...nel.org" <shawnguo@...nel.org>,
"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
"kernel@...gutronix.de" <kernel@...gutronix.de>,
"festevam@...il.com" <festevam@...il.com>,
"linux@...linux.org.uk" <linux@...linux.org.uk>,
"stefan@...er.ch" <stefan@...er.ch>,
"otavio@...ystems.com.br" <otavio@...ystems.com.br>,
Leonard Crestez <leonard.crestez@....com>,
Robin Gong <yibin.gong@....com>,
"linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH V11 2/5] pwm: Add i.MX TPM PWM driver support
Hello,
On Wed, Apr 10, 2019 at 01:47:40AM +0000, Anson Huang wrote:
> i.MX7ULP has TPM(Low Power Timer/Pulse Width Modulation Module)
> inside, it can support multiple PWM channels, all the channels
> share same counter and period setting, but each channel can
> configure its duty and polarity independently.
>
> There are several TPM modules in i.MX7ULP, the number of channels
> in TPM modules are different, it can be read from each TPM module's
> PARAM register.
>
> Signed-off-by: Anson Huang <Anson.Huang@....com>
> ---
> Changes since V10:
> - remove channel private data which is ONLY for storing polarity, just read it from HW register;
> - improve pwm_imx_tpm_round_state() and pwm_imx_tpm_apply_hw() parameters sequence;
> - improve comments for polarity setting;
> - refuse polarity change if PWM is active.
> ---
> drivers/pwm/Kconfig | 11 ++
> drivers/pwm/Makefile | 1 +
> drivers/pwm/pwm-imx-tpm.c | 442 ++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 454 insertions(+)
> create mode 100644 drivers/pwm/pwm-imx-tpm.c
>
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index c054bd1..1311b540 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -210,6 +210,17 @@ config PWM_IMX27
> To compile this driver as a module, choose M here: the module
> will be called pwm-imx27.
>
> +config PWM_IMX_TPM
> + tristate "i.MX TPM PWM support"
> + depends on ARCH_MXC || COMPILE_TEST
> + depends on HAVE_CLK && HAS_IOMEM
> + help
> + Generic PWM framework driver for i.MX7ULP TPM module, TPM's full
> + name is Low Power Timer/Pulse Width Modulation Module.
> +
> + To compile this driver as a module, choose M here: the module
> + will be called pwm-imx-tpm.
> +
> config PWM_JZ4740
> tristate "Ingenic JZ47xx PWM support"
> depends on MACH_INGENIC
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index 448825e..c368599 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -19,6 +19,7 @@ obj-$(CONFIG_PWM_HIBVT) += pwm-hibvt.o
> obj-$(CONFIG_PWM_IMG) += pwm-img.o
> 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_JZ4740) += pwm-jz4740.o
> obj-$(CONFIG_PWM_LP3943) += pwm-lp3943.o
> obj-$(CONFIG_PWM_LPC18XX_SCT) += pwm-lpc18xx-sct.o
> diff --git a/drivers/pwm/pwm-imx-tpm.c b/drivers/pwm/pwm-imx-tpm.c
> new file mode 100644
> index 0000000..9349f4f
> --- /dev/null
> +++ b/drivers/pwm/pwm-imx-tpm.c
> @@ -0,0 +1,442 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2018-2019 NXP.
> + *
> + * Limitations:
> + * - The TPM counter and period counter are shared between
> + * multiple channels, so all channels should use same period
> + * settings.
> + * - Changes to polarity cannot be latched at the time of the
> + * next period start.
> + * - Changing period and duty cycle together isn't atomic,
> + * with the wrong timing it might happen that a period is
> + * produced with old duty cycle but new period settings.
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/bitops.h>
> +#include <linux/clk.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/log2.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +#include <linux/slab.h>
> +
> +#define PWM_IMX_TPM_PARAM 0x4
> +#define PWM_IMX_TPM_GLOBAL 0x8
> +#define PWM_IMX_TPM_SC 0x10
> +#define PWM_IMX_TPM_CNT 0x14
> +#define PWM_IMX_TPM_MOD 0x18
> +#define PWM_IMX_TPM_CnSC(n) (0x20 + (n) * 0x8)
> +#define PWM_IMX_TPM_CnV(n) (0x24 + (n) * 0x8)
> +
> +#define PWM_IMX_TPM_PARAM_CHAN GENMASK(7, 0)
> +
> +#define PWM_IMX_TPM_SC_PS GENMASK(2, 0)
> +#define PWM_IMX_TPM_SC_CMOD GENMASK(4, 3)
> +#define PWM_IMX_TPM_SC_CMOD_INC_EVERY_CLK FIELD_PREP(PWM_IMX_TPM_SC_CMOD, 1)
> +#define PWM_IMX_TPM_SC_CPWMS BIT(5)
> +
> +#define PWM_IMX_TPM_CnSC_CHF BIT(7)
> +#define PWM_IMX_TPM_CnSC_MSB BIT(5)
> +#define PWM_IMX_TPM_CnSC_MSA BIT(4)
> +
> +/*
> + * The reference manual describes this field as two separate bits. The
> + * semantic of the two bits isn't orthogonal though, so they are treated
> + * together as a 2-bit field here.
> + */
> +#define PWM_IMX_TPM_CnSC_ELS GENMASK(3, 2)
> +#define PWM_IMX_TPM_CnSC_ELS_INVERSED FIELD_PREP(PWM_IMX_TPM_CnSC_ELS, 1)
> +#define PWM_IMX_TPM_CnSC_ELS_NORMAL FIELD_PREP(PWM_IMX_TPM_CnSC_ELS, 2)
> +
> +
> +#define PWM_IMX_TPM_MOD_WIDTH 16
> +#define PWM_IMX_TPM_MOD_MOD GENMASK(PWM_IMX_TPM_MOD_WIDTH - 1, 0)
> +
> +struct imx_tpm_pwm_chip {
> + struct pwm_chip chip;
> + struct clk *clk;
> + void __iomem *base;
> + struct mutex lock;
> + u32 user_count;
> + u32 enable_count;
> + u32 real_period;
> +};
> +
> +struct imx_tpm_pwm_param {
> + u8 prescale;
> + u32 mod;
> + u32 val;
> +};
> +
> +static inline struct imx_tpm_pwm_chip *to_imx_tpm_pwm_chip(struct pwm_chip *chip)
> +{
> + return container_of(chip, struct imx_tpm_pwm_chip, chip);
> +}
> +
Maybe add a comment here describing the purpose of this function.
Something like:
/*
* This function determines for a given pwm_state *state that a consumer
* might request the pwm_state *realstate that eventually is implemented
* by the hardware and the necessary register values (in *p) to achive
* this.
*/
I didn't revalidate all the maths in this driver but assume they are
still right from the previous rounds. If you add the comment I suggested
above, feel free to also add
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> +static int pwm_imx_tpm_round_state(struct pwm_chip *chip,
> + struct imx_tpm_pwm_param *p,
> + struct pwm_state *real_state,
> + struct pwm_state *state)
> +{
> + struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
> + u32 rate, prescale, period_count, clock_unit;
> + u64 tmp;
> +
> + rate = clk_get_rate(tpm->clk);
> + tmp = (u64)state->period * rate;
> + clock_unit = DIV_ROUND_CLOSEST_ULL(tmp, NSEC_PER_SEC);
> + if (clock_unit <= PWM_IMX_TPM_MOD_MOD)
> + prescale = 0;
> + else
> + prescale = ilog2(clock_unit) + 1 - PWM_IMX_TPM_MOD_WIDTH;
> +
> + if ((!FIELD_FIT(PWM_IMX_TPM_SC_PS, prescale)))
> + return -ERANGE;
It's a bit sad that my ideas for the core concerning a round_rate
callback don't go down particularly well on Thierry's side.
With the way I suggested we'd continue with prescale = 7 in this case.
As of now there is no rule which kind of deviation to accept and which
not. :-| (Nothing this patch can change of course.)
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
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