Re: [PATCH v2 3/5] i2c: i2c-stm32f7: add driver

From: Uwe Kleine-König
Date: Tue Jun 27 2017 - 16:54:21 EST

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Hello,

just a quick review as last act in the night. I don't claim to catch
everything at this time of the day. So don't be surprised if I still
find something to criticize after you fixed everything. But keeping this
until I find time to look again seems wrong to me.

On Tue, Jun 20, 2017 at 01:41:28PM +0200, Pierre-Yves MORDRET wrote:
> This patch adds initial support for the STM32F7 I2C controller.
>
> Signed-off-by: M'boumba Cedric Madianga <cedric.madianga@xxxxxxxxx>
> Signed-off-by: Pierre-Yves MORDRET <pierre-yves.mordret@xxxxxx>
> ---
> Changes in V2:
> * Remove st,i2c-timing binding usage
> * Implement an I2C timings computation algorithm instead of static
> values(bindings). Algorithm uses generic I2C SCL Falling/Rising
> bindings and System clock to compute its timings.
> ---
> drivers/i2c/busses/Kconfig | 10 +
> drivers/i2c/busses/Makefile | 1 +
> drivers/i2c/busses/i2c-stm32f7.c | 968 +++++++++++++++++++++++++++++++++++++++
> 3 files changed, 979 insertions(+)
> create mode 100644 drivers/i2c/busses/i2c-stm32f7.c
>
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index ed7106e..a97b987 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -899,6 +899,16 @@ config I2C_STM32F4
> This driver can also be built as module. If so, the module
> will be called i2c-stm32f4.
>
> +config I2C_STM32F7
> + tristate "STMicroelectronics STM32F7 I2C support"
> + depends on ARCH_STM32 || COMPILE_TEST
> + help
> + Enable this option to add support for STM32 I2C controller embedded
> + in STM32F7 SoCs.
> +
> + This driver can also be built as module. If so, the module
> + will be called i2c-stm32f7.
> +

I wonder how similar I2C_STM32F4 and I2C_STM32F7 are. There is hardly
any code sharing between them. Can this be improved?

> config I2C_STU300
> tristate "ST Microelectronics DDC I2C interface"
> depends on MACH_U300
> diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> index c89a431..8efa3dd 100644
> --- a/drivers/i2c/busses/Makefile
> +++ b/drivers/i2c/busses/Makefile
> @@ -87,6 +87,7 @@ obj-$(CONFIG_I2C_SIMTEC) += i2c-simtec.o
> obj-$(CONFIG_I2C_SIRF) += i2c-sirf.o
> obj-$(CONFIG_I2C_ST) += i2c-st.o
> obj-$(CONFIG_I2C_STM32F4) += i2c-stm32f4.o
> +obj-$(CONFIG_I2C_STM32F7) += i2c-stm32f7.o
> obj-$(CONFIG_I2C_STU300) += i2c-stu300.o
> obj-$(CONFIG_I2C_SUN6I_P2WI) += i2c-sun6i-p2wi.o
> obj-$(CONFIG_I2C_TEGRA) += i2c-tegra.o
> diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
> new file mode 100644
> index 0000000..9947a9d
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-stm32f7.c
> @@ -0,0 +1,968 @@
> +/*
> + * Driver for STMicroelectronics STM32F7 I2C controller
> + *
> + * This I2C controller is described in the STM32F75xxx and STM32F74xxx Soc
> + * reference manual.
> + * Please see below a link to the documentation:
> + * http://www.st.com/resource/en/reference_manual/dm00124865.pdf
> + *
> + * Copyright (C) M'boumba Cedric Madianga 2017
> + * Author: M'boumba Cedric Madianga <cedric.madianga@xxxxxxxxx>
> + *
> + * This driver is based on i2c-stm32f4.c
> + *
> + * License terms: GNU General Public License (GPL), version 2
> + */
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/iopoll.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> +#include <linux/reset.h>
> +#include <linux/slab.h>
> +
> +#include "i2c-stm32.h"
> +
> +/* STM32F7 I2C registers */
> +#define STM32F7_I2C_CR1 0x00
> +#define STM32F7_I2C_CR2 0x04
> +#define STM32F7_I2C_TIMINGR 0x10
> +#define STM32F7_I2C_ISR 0x18
> +#define STM32F7_I2C_ICR 0x1C
> +#define STM32F7_I2C_RXDR 0x24
> +#define STM32F7_I2C_TXDR 0x28

puh, this is really different than the f4 variant. Yet another hw
engineer that likes keeping the sw guys busy :-|

> +/* STM32F7 I2C control 1 */
> +#define STM32F7_I2C_CR1_ANFOFF BIT(12)
> +#define STM32F7_I2C_CR1_ERRIE BIT(7)
> +#define STM32F7_I2C_CR1_TCIE BIT(6)
> +#define STM32F7_I2C_CR1_STOPIE BIT(5)
> +#define STM32F7_I2C_CR1_NACKIE BIT(4)
> +#define STM32F7_I2C_CR1_ADDRIE BIT(3)
> +#define STM32F7_I2C_CR1_RXIE BIT(2)
> +#define STM32F7_I2C_CR1_TXIE BIT(1)
> +#define STM32F7_I2C_CR1_PE BIT(0)
> +#define STM32F7_I2C_ALL_IRQ_MASK (STM32F7_I2C_CR1_ERRIE \
> + | STM32F7_I2C_CR1_TCIE \
> + | STM32F7_I2C_CR1_STOPIE \
> + | STM32F7_I2C_CR1_NACKIE \
> + | STM32F7_I2C_CR1_RXIE \
> + | STM32F7_I2C_CR1_TXIE)
> +
> +/* STM32F7 I2C control 2 */
> +#define STM32F7_I2C_CR2_RELOAD BIT(24)
> +#define STM32F7_I2C_CR2_NBYTES_MASK GENMASK(23, 16)
> +#define STM32F7_I2C_CR2_NBYTES(n) (((n) & 0xff) << 16)
> +#define STM32F7_I2C_CR2_NACK BIT(15)
> +#define STM32F7_I2C_CR2_STOP BIT(14)
> +#define STM32F7_I2C_CR2_START BIT(13)
> +#define STM32F7_I2C_CR2_RD_WRN BIT(10)
> +#define STM32F7_I2C_CR2_SADD7_MASK GENMASK(7, 1)
> +#define STM32F7_I2C_CR2_SADD7(n) (((n) & 0x7f) << 1)
> +
> +/* STM32F7 I2C Interrupt Status */
> +#define STM32F7_I2C_ISR_BUSY BIT(15)
> +#define STM32F7_I2C_ISR_ARLO BIT(9)
> +#define STM32F7_I2C_ISR_BERR BIT(8)
> +#define STM32F7_I2C_ISR_TCR BIT(7)
> +#define STM32F7_I2C_ISR_TC BIT(6)
> +#define STM32F7_I2C_ISR_STOPF BIT(5)
> +#define STM32F7_I2C_ISR_NACKF BIT(4)
> +#define STM32F7_I2C_ISR_RXNE BIT(2)
> +#define STM32F7_I2C_ISR_TXIS BIT(1)
> +
> +/* STM32F7 I2C Interrupt Clear */
> +#define STM32F7_I2C_ICR_ARLOCF BIT(9)
> +#define STM32F7_I2C_ICR_BERRCF BIT(8)
> +#define STM32F7_I2C_ICR_STOPCF BIT(5)
> +#define STM32F7_I2C_ICR_NACKCF BIT(4)
> +
> +/* STM32F7 I2C Timing */
> +#define STM32F7_I2C_TIMINGR_PRESC(n) (((n) & 0xf) << 28)
> +#define STM32F7_I2C_TIMINGR_SCLDEL(n) (((n) & 0xf) << 20)
> +#define STM32F7_I2C_TIMINGR_SDADEL(n) (((n) & 0xf) << 16)
> +#define STM32F7_I2C_TIMINGR_SCLH(n) (((n) & 0xff) << 8)
> +#define STM32F7_I2C_TIMINGR_SCLL(n) ((n) & 0xff)
> +
> +#define STM32F7_I2C_MAX_LEN 0xff
> +
> +#define STM32F7_I2C_DNF_DEFAULT 0
> +#define STM32F7_I2C_DNF_MAX 16
> +
> +#define STM32F7_I2C_ANALOG_FILTER_ENABLE 1
> +#define STM32F7_I2C_ANALOG_FILTER_DELAY_MIN 50 /* ns */
> +#define STM32F7_I2C_ANALOG_FILTER_DELAY_MAX 260 /* ns */
> +
> +#define STM32F7_I2C_RISE_TIME_DEFAULT 25 /* ns */
> +#define STM32F7_I2C_FALL_TIME_DEFAULT 10 /* ns */
> +
> +#define STM32F7_PRESC_MAX BIT(4)
> +#define STM32F7_SCLDEL_MAX BIT(4)
> +#define STM32F7_SDADEL_MAX BIT(4)
> +#define STM32F7_SCLH_MAX BIT(8)
> +#define STM32F7_SCLL_MAX BIT(8)
> +
> +/**
> + * struct stm32f7_i2c_spec - private i2c specification timing
> + * @rate: I2C bus speed (Hz)
> + * @rate_min: 80% of I2C bus speed (Hz)
> + * @rate_max: 120% of I2C bus speed (Hz)
> + * @fall_max: Max fall time of both SDA and SCL signals (ns)
> + * @rise_max: Max rise time of both SDA and SCL signals (ns)
> + * @hddat_min: Min data hold time (ns)
> + * @vddat_max: Max data valid time (ns)
> + * @sudat_min: Min data setup time (ns)
> + * @l_min: Min low period of the SCL clock (ns)
> + * @h_min: Min high period of the SCL clock (ns)
> + */
> +

drop this empty line please.

> +struct stm32f7_i2c_spec {
> + u32 rate;
> + u32 rate_min;
> + u32 rate_max;
> + u32 fall_max;
> + u32 rise_max;
> + u32 hddat_min;
> + u32 vddat_max;
> + u32 sudat_min;
> + u32 l_min;
> + u32 h_min;
> +};
> +
> +/**
> + * struct stm32f7_i2c_setup - private I2C timing setup parameters
> + * @speed: I2C speed mode (standard, Fast Plus)
> + * @speed_freq: I2C speed frequency (Hz)
> + * @clock_src: I2C clock source frequency (Hz)
> + * @rise_time: Rise time (ns)
> + * @fall_time: Fall time (ns)
> + * @dnf: Digital filter coefficient (0-16)
> + * @analog_filter: Analog filter delay (On/Off)
> + */
> +struct stm32f7_i2c_setup {
> + enum stm32_i2c_speed speed;
> + u32 speed_freq;
> + u32 clock_src;
> + u32 rise_time;
> + u32 fall_time;
> + u8 dnf;
> + bool analog_filter;
> +};
> +
> +/**
> + * struct stm32f7_i2c_timings - private I2C output parameters
> + * @prec: Prescaler value
> + * @scldel: Data setup time
> + * @sdadel: Data hold time
> + * @sclh: SCL high period (master mode)
> + * @sclh: SCL low period (master mode)
> + */
> +struct stm32f7_i2c_timings {
> + struct list_head node;
> + u8 presc;
> + u8 scldel;
> + u8 sdadel;
> + u8 sclh;
> + u8 scll;
> +};
> +
> +/**
> + * struct stm32f7_i2c_msg - client specific data
> + * @addr: 8-bit slave addr, including r/w bit
> + * @count: number of bytes to be transferred
> + * @buf: data buffer
> + * @result: result of the transfer
> + * @stop: last I2C msg to be sent, i.e. STOP to be generated
> + */
> +struct stm32f7_i2c_msg {
> + u8 addr;
> + u32 count;
> + u8 *buf;
> + int result;
> + bool stop;
> +};
> +
> +/**
> + * struct stm32f7_i2c_dev - private data of the controller
> + * @adap: I2C adapter for this controller
> + * @dev: device for this controller
> + * @base: virtual memory area
> + * @complete: completion of I2C message
> + * @clk: hw i2c clock
> + * @speed: I2C clock frequency of the controller. Standard, Fast or Fast+
> + * @msg: Pointer to data to be written
> + * @msg_num: number of I2C messages to be executed
> + * @msg_id: message identifiant
> + * @f7_msg: customized i2c msg for driver usage
> + * @setup: I2C timing input setup
> + * @timing: I2C computed timings
> + */
> +struct stm32f7_i2c_dev {
> + struct i2c_adapter adap;
> + struct device *dev;
> + void __iomem *base;
> + struct completion complete;
> + struct clk *clk;
> + int speed;
> + struct i2c_msg *msg;
> + unsigned int msg_num;
> + unsigned int msg_id;
> + struct stm32f7_i2c_msg f7_msg;
> + struct stm32f7_i2c_setup *setup;
> + struct stm32f7_i2c_timings timing;
> +};
> +
> +static struct stm32f7_i2c_spec i2c_specs[] = {
> + [STM32_I2C_SPEED_STANDARD] = {
> + .rate = 100000,
> + .rate_min = 8000,
> + .rate_max = 120000,
> + .fall_max = 300,
> + .rise_max = 1000,
> + .hddat_min = 0,
> + .vddat_max = 3450,
> + .sudat_min = 250,
> + .l_min = 4700,
> + .h_min = 4000,
> + },
> + [STM32_I2C_SPEED_FAST] = {
> + .rate = 400000,
> + .rate_min = 320000,
> + .rate_max = 480000,
> + .fall_max = 300,
> + .rise_max = 300,
> + .hddat_min = 0,
> + .vddat_max = 900,
> + .sudat_min = 100,
> + .l_min = 1300,
> + .h_min = 600,
> + },
> + [STM32_I2C_SPEED_FAST_PLUS] = {
> + .rate = 1000000,
> + .rate_min = 800000,
> + .rate_max = 1200000,
> + .fall_max = 100,
> + .rise_max = 120,
> + .hddat_min = 0,
> + .vddat_max = 450,
> + .sudat_min = 50,
> + .l_min = 500,
> + .h_min = 260,
> + },
> +};

What is the source of the above table? Maybe mention it in a comment?
I don't like adding white space to align the =. The next person touching
this either breaks the alignment or has to modify more than
syntactically necessary.

> +struct stm32f7_i2c_setup stm32f7_setup = {
> + .rise_time = STM32F7_I2C_RISE_TIME_DEFAULT,
> + .fall_time = STM32F7_I2C_FALL_TIME_DEFAULT,
> + .dnf = STM32F7_I2C_DNF_DEFAULT,
> + .analog_filter = STM32F7_I2C_ANALOG_FILTER_ENABLE,
> +};
> +
> +static inline void stm32f7_i2c_set_bits(void __iomem *reg, u32 mask)
> +{
> + writel_relaxed(readl_relaxed(reg) | mask, reg);
> +}

this is used three times only. Among these two times
stm32f7_i2c_hw_config(). I wonder if it would be more robust to assign a
complete value to the registers there and then drop this function and
open code it for the last user.

> +
> +static inline void stm32f7_i2c_clr_bits(void __iomem *reg, u32 mask)
> +{
> + writel_relaxed(readl_relaxed(reg) & ~mask, reg);
> +}

Two users only, same thoughts as for stm32f7_i2c_set_bits.

> +
> +static int stm32f7_i2c_compute_timing(struct stm32f7_i2c_dev *i2c_dev,
> + struct stm32f7_i2c_setup *setup,
> + struct stm32f7_i2c_timings *output)
> +{
> + u32 p_prev = STM32F7_PRESC_MAX;
> + u32 i2cclk = DIV_ROUND_CLOSEST(NSEC_PER_SEC,
> + setup->clock_src);
> + u32 i2cbus = DIV_ROUND_CLOSEST(NSEC_PER_SEC,
> + setup->speed_freq);
> + u32 clk_error_prev = i2cbus;
> + u32 tsync;
> + u32 af_delay_min, af_delay_max;
> + u32 dnf_delay;
> + u32 clk_min, clk_max;
> + int sdadel_min, sdadel_max;
> + int scldel_min;
> + struct stm32f7_i2c_timings *v, *_v, *s;
> + struct list_head solutions;
> + u16 p, l, a, h;
> + int ret = 0;
> +
> + if (setup->speed >= STM32_I2C_SPEED_END) {
> + dev_err(i2c_dev->dev, "speed out of bound {%d/%d}\n",
> + setup->speed, STM32_I2C_SPEED_END - 1);
> + return -EINVAL;
> + }
> +
> + if ((setup->rise_time > i2c_specs[setup->speed].rise_max) ||
> + (setup->fall_time > i2c_specs[setup->speed].fall_max)) {
> + dev_err(i2c_dev->dev,
> + "timings out of bound Rise{%d>%d}/Fall{%d>%d}\n",
> + setup->rise_time, i2c_specs[setup->speed].rise_max,
> + setup->fall_time, i2c_specs[setup->speed].fall_max);
> + return -EINVAL;
> + }
> +
> + if (setup->dnf > STM32F7_I2C_DNF_MAX) {
> + dev_err(i2c_dev->dev,
> + "DNF out of bound %d/%d\n",
> + setup->dnf, STM32F7_I2C_DNF_MAX);
> + return -EINVAL;
> + }
> +
> + if (setup->speed_freq > i2c_specs[setup->speed].rate) {
> + dev_err(i2c_dev->dev, "ERROR: Freq {%d/%d}\n",
> + setup->speed_freq, i2c_specs[setup->speed].rate);
> + return -EINVAL;
> + }
> +
> + /* Analog and Digital Filters */
> + af_delay_min =
> + (setup->analog_filter ?
> + STM32F7_I2C_ANALOG_FILTER_DELAY_MIN : 0);
> + af_delay_max =
> + (setup->analog_filter ?
> + STM32F7_I2C_ANALOG_FILTER_DELAY_MAX : 0);
> + dnf_delay = setup->dnf * i2cclk;
> +
> + sdadel_min = setup->fall_time - i2c_specs[setup->speed].hddat_min -
> + af_delay_min - (setup->dnf + 3) * i2cclk;
> +
> + sdadel_max = i2c_specs[setup->speed].vddat_max - setup->rise_time -
> + af_delay_max - (setup->dnf + 4) * i2cclk;
> +
> + scldel_min = setup->rise_time + i2c_specs[setup->speed].sudat_min;
> +
> + if (sdadel_min < 0)
> + sdadel_min = 0;
> + if (sdadel_max < 0)
> + sdadel_max = 0;
> +
> + dev_dbg(i2c_dev->dev, "SDADEL(min/max): %i/%i, SCLDEL(Min): %i\n",
> + sdadel_min, sdadel_max, scldel_min);
> +
> + INIT_LIST_HEAD(&solutions);
> + /* Compute possible values for PRESC, SCLDEL and SDADEL */
> + for (p = 0; p < STM32F7_PRESC_MAX; p++) {
> + for (l = 0; l < STM32F7_SCLDEL_MAX; l++) {
> + u32 scldel = (l + 1) * (p + 1) * i2cclk;
> +
> + if (scldel < scldel_min)
> + continue;
> +
> + for (a = 0; a < STM32F7_SDADEL_MAX; a++) {
> + u32 sdadel = (a * (p + 1) + 1) * i2cclk;
> +
> + if (((sdadel >= sdadel_min) &&
> + (sdadel <= sdadel_max)) &&
> + (p != p_prev)) {
> + v = kmalloc(sizeof(*v), GFP_KERNEL);
> + if (!v) {
> + ret = -ENOMEM;
> + goto exit;
> + }
> +
> + v->presc = p;
> + v->scldel = l;
> + v->sdadel = a;
> + p_prev = p;
> +
> + list_add_tail(&v->node,
> + &solutions);
> + }
> + }
> + }
> + }
> +
> + if (list_empty(&solutions)) {
> + dev_err(i2c_dev->dev, "no Prescaler solution\n");
> + ret = -EPERM;
> + goto exit;
> + }
> +
> + tsync = af_delay_min + dnf_delay + (2 * i2cclk);
> + s = NULL;
> + clk_max = NSEC_PER_SEC / i2c_specs[setup->speed].rate_min;
> + clk_min = NSEC_PER_SEC / i2c_specs[setup->speed].rate_max;
> +
> + /*
> + * Among Prescaler possibilities discovered above figures out SCL Low
> + * and High Period. Provided:
> + * - SCL Low Period has to be higher than Low Period of tehs SCL Clock
> + * defined by I2C Specification. I2C Clock has to be lower than
> + * (SCL Low Period - Analog/Digital filters) / 4.
> + * - SCL High Period has to be lower than High Period of the SCL Clock
> + * defined by I2C Specification
> + * - I2C Clock has to be lower than SCL High Period
> + */
> + list_for_each_entry(v, &solutions, node) {
> + u32 prescaler = (v->presc + 1) * i2cclk;
> +
> + for (l = 0; l < STM32F7_SCLL_MAX; l++) {
> + u32 tscl_l = (l + 1) * prescaler + tsync;
> +
> + if ((tscl_l < i2c_specs[setup->speed].l_min) ||
> + (i2cclk >=
> + ((tscl_l - af_delay_min - dnf_delay) / 4))) {
> + continue;
> + }
> +
> + for (h = 0; h < STM32F7_SCLH_MAX; h++) {
> + u32 tscl_h = (h + 1) * prescaler + tsync;
> + u32 tscl = tscl_l + tscl_h +
> + setup->rise_time + setup->fall_time;
> +
> + if ((tscl >= clk_min) && (tscl <= clk_max) &&
> + (tscl_h >= i2c_specs[setup->speed].h_min) &&
> + (i2cclk < tscl_h)) {
> + int clk_error = tscl - i2cbus;
> +
> + if (clk_error < 0)
> + clk_error = -clk_error;
> +
> + if (clk_error < clk_error_prev) {
> + clk_error_prev = clk_error;
> + v->scll = l;
> + v->sclh = h;
> + s = v;
> + }
> + }
> + }
> + }
> + }
> +
> + if (!s) {
> + dev_err(i2c_dev->dev, "no solution at all\n");
> + ret = -EPERM;
> + goto exit;
> + }
> +
> + output->presc = s->presc;
> + output->scldel = s->scldel;
> + output->sdadel = s->sdadel;
> + output->scll = s->scll;
> + output->sclh = s->sclh;
> +
> + dev_dbg(i2c_dev->dev,
> + "Presc: %i, scldel: %i, sdadel: %i, scll: %i, sclh: %i\n",
> + output->presc,
> + output->scldel, output->sdadel,
> + output->scll, output->sclh);
> +
> +exit:
> + /* Release list and memory */
> + list_for_each_entry_safe(v, _v, &solutions, node) {
> + list_del(&v->node);
> + kfree(v);
> + }
> +
> + return ret;
> +}
> +
> +static int stm32f7_i2c_setup_timing(struct stm32f7_i2c_dev *i2c_dev,
> + struct stm32f7_i2c_setup *setup)
> +{
> + int ret = 0;
> +
> + setup->speed = i2c_dev->speed;
> + setup->speed_freq = i2c_specs[setup->speed].rate;
> + setup->clock_src = clk_get_rate(i2c_dev->clk);
> +
> + if (!setup->clock_src) {
> + dev_err(i2c_dev->dev, "clock rate is 0\n");
> + return -EINVAL;
> + }
> +
> + do {
> + ret = stm32f7_i2c_compute_timing(i2c_dev, setup,
> + &i2c_dev->timing);
> + if (ret) {
> + dev_err(i2c_dev->dev,
> + "failed to compute I2C timings.\n");
> + if (i2c_dev->speed > STM32_I2C_SPEED_STANDARD) {
> + i2c_dev->speed--;
> + setup->speed = i2c_dev->speed;
> + setup->speed_freq =
> + i2c_specs[setup->speed].rate;
> + dev_warn(i2c_dev->dev,
> + "downgrade I2C Speed Freq to (%i)\n",
> + i2c_specs[setup->speed].rate);
> + } else {
> + break;
> + }
> + }
> + } while (ret);
> +
> + if (ret) {
> + dev_err(i2c_dev->dev, "Impossible to compute I2C timings.\n");
> + return ret;
> + }
> +
> + dev_dbg(i2c_dev->dev, "I2C Speed(%i), Freq(%i), Clk Source(%i)\n",
> + setup->speed, setup->speed_freq, setup->clock_src);
> + dev_dbg(i2c_dev->dev, "I2C Rise(%i) and Fall(%i) Time\n",
> + setup->rise_time, setup->fall_time);
> + dev_dbg(i2c_dev->dev, "I2C Analog Filter(%s), DNF(%i)\n",
> + (setup->analog_filter ? "On" : "Off"), setup->dnf);
> +
> + i2c_dev->setup = setup;
> +
> + return 0;
> +}
> +
> +static void stm32f7_i2c_hw_config(struct stm32f7_i2c_dev *i2c_dev)
> +{
> + struct stm32f7_i2c_timings *t = &i2c_dev->timing;
> + u32 timing = 0;
> +
> + /* Timing settings */
> + timing |= STM32F7_I2C_TIMINGR_PRESC(t->presc);
> + timing |= STM32F7_I2C_TIMINGR_SCLDEL(t->scldel);
> + timing |= STM32F7_I2C_TIMINGR_SDADEL(t->sdadel);
> + timing |= STM32F7_I2C_TIMINGR_SCLH(t->sclh);
> + timing |= STM32F7_I2C_TIMINGR_SCLL(t->scll);
> + writel_relaxed(timing, i2c_dev->base + STM32F7_I2C_TIMINGR);
> +
> + /* Enable I2C */
> + if (i2c_dev->setup->analog_filter)
> + stm32f7_i2c_clr_bits(i2c_dev->base + STM32F7_I2C_CR1,
> + STM32F7_I2C_CR1_ANFOFF);
> + else
> + stm32f7_i2c_set_bits(i2c_dev->base + STM32F7_I2C_CR1,
> + STM32F7_I2C_CR1_ANFOFF);
> + stm32f7_i2c_set_bits(i2c_dev->base + STM32F7_I2C_CR1,
> + STM32F7_I2C_CR1_PE);
> +}
> +
> +static void stm32f7_i2c_write_tx_data(struct stm32f7_i2c_dev *i2c_dev)
> +{
> + struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
> + void __iomem *base = i2c_dev->base;
> +
> + if (f7_msg->count) {
> + writeb_relaxed(*f7_msg->buf++, base + STM32F7_I2C_TXDR);
> + f7_msg->count--;
> + }
> +}
> +
> +static void stm32f7_i2c_read_rx_data(struct stm32f7_i2c_dev *i2c_dev)
> +{
> + struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
> + void __iomem *base = i2c_dev->base;
> +
> + if (f7_msg->count) {
> + *f7_msg->buf++ = readb_relaxed(base + STM32F7_I2C_RXDR);
> + f7_msg->count--;
> + }
> +}
> +
> +static void stm32f7_i2c_reload(struct stm32f7_i2c_dev *i2c_dev)
> +{
> + struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
> + u32 cr2;
> +
> + cr2 = readl_relaxed(i2c_dev->base + STM32F7_I2C_CR2);
> +
> + cr2 &= ~STM32F7_I2C_CR2_NBYTES_MASK;
> + if (f7_msg->count > STM32F7_I2C_MAX_LEN) {
> + cr2 |= STM32F7_I2C_CR2_NBYTES(STM32F7_I2C_MAX_LEN);
> + } else {
> + cr2 &= ~STM32F7_I2C_CR2_RELOAD;
> + cr2 |= STM32F7_I2C_CR2_NBYTES(f7_msg->count);
> + }
> +
> + writel_relaxed(cr2, i2c_dev->base + STM32F7_I2C_CR2);
> +}
> +
> +static int stm32f7_i2c_wait_free_bus(struct stm32f7_i2c_dev *i2c_dev)
> +{
> + u32 status;
> + int ret;
> +
> + ret = readl_relaxed_poll_timeout(i2c_dev->base + STM32F7_I2C_ISR,
> + status,
> + !(status & STM32F7_I2C_ISR_BUSY),
> + 10, 1000);
> + if (ret) {
> + dev_dbg(i2c_dev->dev, "bus busy\n");
> + ret = -EBUSY;
> + }
> +
> + return ret;
> +}
> +
> +static void stm32f7_i2c_xfer_msg(struct stm32f7_i2c_dev *i2c_dev,
> + struct i2c_msg *msg)
> +{
> + struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
> + void __iomem *base = i2c_dev->base;
> + u32 cr1, cr2;
> +
> + f7_msg->addr = msg->addr;
> + f7_msg->buf = msg->buf;
> + f7_msg->count = msg->len;
> + f7_msg->result = 0;
> + f7_msg->stop = (i2c_dev->msg_id >= i2c_dev->msg_num - 1);
> +
> + reinit_completion(&i2c_dev->complete);
> +
> + cr1 = readl_relaxed(base + STM32F7_I2C_CR1);
> + cr2 = readl_relaxed(base + STM32F7_I2C_CR2);

Can you know the content of these registers from the context?

> + /* Set transfer direction */
> + cr2 &= ~STM32F7_I2C_CR2_RD_WRN;
> + if (msg->flags & I2C_M_RD)
> + cr2 |= STM32F7_I2C_CR2_RD_WRN;
> +
> + /* Set slave address */
> + cr2 &= ~STM32F7_I2C_CR2_SADD7_MASK;
> + cr2 |= STM32F7_I2C_CR2_SADD7(f7_msg->addr);
> +
> + /* Set nb bytes to transfer and reload if needed */
> + cr2 &= ~(STM32F7_I2C_CR2_NBYTES_MASK | STM32F7_I2C_CR2_RELOAD);
> + if (f7_msg->count > STM32F7_I2C_MAX_LEN) {
> + cr2 |= STM32F7_I2C_CR2_NBYTES(STM32F7_I2C_MAX_LEN);
> + cr2 |= STM32F7_I2C_CR2_RELOAD;
> + } else {
> + cr2 |= STM32F7_I2C_CR2_NBYTES(f7_msg->count);
> + }
> +
> + /* Enable NACK, STOP, error and transfer complete interrupts */
> + cr1 |= STM32F7_I2C_CR1_ERRIE | STM32F7_I2C_CR1_TCIE |
> + STM32F7_I2C_CR1_STOPIE | STM32F7_I2C_CR1_NACKIE;
> +
> + /* Clear TX/RX interrupt */
> + cr1 &= ~(STM32F7_I2C_CR1_RXIE | STM32F7_I2C_CR1_TXIE);
> +
> + /* Enable RX/TX interrupt according to msg direction */
> + if (msg->flags & I2C_M_RD)
> + cr1 |= STM32F7_I2C_CR1_RXIE;
> + else
> + cr1 |= STM32F7_I2C_CR1_TXIE;
> +
> + /* Configure Start/Repeated Start */
> + cr2 |= STM32F7_I2C_CR2_START;
> +
> + /* Write configurations registers */
> + writel_relaxed(cr1, base + STM32F7_I2C_CR1);
> + writel_relaxed(cr2, base + STM32F7_I2C_CR2);
> +}
> +
> +static void stm32f7_i2c_disable_irq(struct stm32f7_i2c_dev *i2c_dev, u32 mask)
> +{
> + stm32f7_i2c_clr_bits(i2c_dev->base + STM32F7_I2C_CR1, mask);
> +}

mask is always STM32F7_I2C_ALL_IRQ_MASK. Maybe use this to simplify?

> +static irqreturn_t stm32f7_i2c_isr_event(int irq, void *data)
> +{
> + struct stm32f7_i2c_dev *i2c_dev = data;
> + struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
> + void __iomem *base = i2c_dev->base;
> + u32 status, mask;
> +
> + status = readl_relaxed(i2c_dev->base + STM32F7_I2C_ISR);
> +
> + /* Tx empty */
> + if (status & STM32F7_I2C_ISR_TXIS)
> + stm32f7_i2c_write_tx_data(i2c_dev);
> +
> + /* RX not empty */
> + if (status & STM32F7_I2C_ISR_RXNE)
> + stm32f7_i2c_read_rx_data(i2c_dev);
> +
> + /* NACK received */
> + if (status & STM32F7_I2C_ISR_NACKF) {
> + dev_dbg(i2c_dev->dev, "<%s>: Receive NACK\n", __func__);
> + writel_relaxed(STM32F7_I2C_ICR_NACKCF, base + STM32F7_I2C_ICR);
> + f7_msg->result = -EBADE;
> + }
> +
> + /* STOP detection flag */
> + if (status & STM32F7_I2C_ISR_STOPF) {
> + /* Disable interrupts */
> + stm32f7_i2c_disable_irq(i2c_dev, STM32F7_I2C_ALL_IRQ_MASK);
> +
> + /* Clear STOP flag */
> + writel_relaxed(STM32F7_I2C_ICR_STOPCF, base + STM32F7_I2C_ICR);
> +
> + complete(&i2c_dev->complete);
> + }
> +
> + /* Transfer complete */
> + if (status & STM32F7_I2C_ISR_TC) {
> + if (f7_msg->stop) {
> + mask = STM32F7_I2C_CR2_STOP;
> + stm32f7_i2c_set_bits(base + STM32F7_I2C_CR2, mask);
> + } else {
> + i2c_dev->msg_id++;
> + i2c_dev->msg++;
> + stm32f7_i2c_xfer_msg(i2c_dev, i2c_dev->msg);
> + }
> + }
> +
> + /*
> + * Transfer Complete Reload: 255 data bytes have been transferred
> + * We have to prepare the I2C controller to transfer the remaining
> + * data

Missing punctuation.

> + */
> + if (status & STM32F7_I2C_ISR_TCR)
> + stm32f7_i2c_reload(i2c_dev);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t stm32f7_i2c_isr_error(int irq, void *data)
> +{
> + struct stm32f7_i2c_dev *i2c_dev = data;
> + struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
> + void __iomem *base = i2c_dev->base;
> + struct device *dev = i2c_dev->dev;
> + u32 status;
> +
> + status = readl_relaxed(i2c_dev->base + STM32F7_I2C_ISR);
> +
> + /* Bus error */
> + if (status & STM32F7_I2C_ISR_BERR) {
> + dev_err(dev, "<%s>: Bus error\n", __func__);
> + writel_relaxed(STM32F7_I2C_ICR_BERRCF, base + STM32F7_I2C_ICR);
> + f7_msg->result = -EIO;
> + }
> +
> + /* Arbitration loss */
> + if (status & STM32F7_I2C_ISR_ARLO) {
> + dev_err(dev, "<%s>: Arbitration loss\n", __func__);

Drop this. Arbitration loss is not an error and it shouldn't pollute the
kernel log.

> + writel_relaxed(STM32F7_I2C_ICR_ARLOCF, base + STM32F7_I2C_ICR);
> + f7_msg->result = -EAGAIN;
> + }
> +
> + stm32f7_i2c_disable_irq(i2c_dev, STM32F7_I2C_ALL_IRQ_MASK);
> +
> + complete(&i2c_dev->complete);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static int stm32f7_i2c_xfer(struct i2c_adapter *i2c_adap,
> + struct i2c_msg msgs[], int num)
> +{
> + struct stm32f7_i2c_dev *i2c_dev = i2c_get_adapdata(i2c_adap);
> + struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
> + unsigned long timeout;
> + int ret;
> +
> + i2c_dev->msg = msgs;
> + i2c_dev->msg_num = num;
> + i2c_dev->msg_id = 0;
> +
> + ret = clk_enable(i2c_dev->clk);
> + if (ret) {
> + dev_err(i2c_dev->dev, "Failed to enable clock\n");
> + return ret;
> + }
> +
> + ret = stm32f7_i2c_wait_free_bus(i2c_dev);
> + if (ret)
> + goto clk_free;
> +
> + stm32f7_i2c_xfer_msg(i2c_dev, msgs);
> +
> + timeout = wait_for_completion_timeout(&i2c_dev->complete,
> + i2c_dev->adap.timeout);
> + ret = f7_msg->result;
> +
> + if (!timeout) {
> + dev_dbg(i2c_dev->dev, "Access to slave 0x%x timed out\n",
> + i2c_dev->msg->addr);
> + ret = -ETIMEDOUT;
> + }
> +
> +clk_free:
> + clk_disable(i2c_dev->clk);
> +
> + return (ret < 0) ? ret : num;
> +}
> +
> +static u32 stm32f7_i2c_func(struct i2c_adapter *adap)
> +{
> + return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
> +}
> +
> +static struct i2c_algorithm stm32f7_i2c_algo = {
> + .master_xfer = stm32f7_i2c_xfer,
> + .functionality = stm32f7_i2c_func,
> +};
> +
> +static const struct of_device_id stm32f7_i2c_match[] = {
> + { .compatible = "st,stm32f7-i2c", .data = &stm32f7_setup},
> + {},
> +};
> +MODULE_DEVICE_TABLE(of, stm32f7_i2c_match);

I thought the naming to be uncommon and wanted to suggest _ids as
suffix. But grep proves me wrong here. I'd like to see this further
down, just above stm32f7_i2c_driver.

> +static int stm32f7_i2c_probe(struct platform_device *pdev)
> +{
> + struct device_node *np = pdev->dev.of_node;
> + const struct of_device_id *match;
> + struct stm32f7_i2c_dev *i2c_dev;
> + struct stm32f7_i2c_setup *setup;
> + struct resource *res;
> + u32 irq_error, irq_event, clk_rate, rise_time, fall_time;
> + struct i2c_adapter *adap;
> + struct reset_control *rst;
> + int ret;
> +
> + i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
> + if (!i2c_dev)
> + return -ENOMEM;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + i2c_dev->base = devm_ioremap_resource(&pdev->dev, res);
> + if (IS_ERR(i2c_dev->base))
> + return PTR_ERR(i2c_dev->base);
> +
> + irq_event = irq_of_parse_and_map(np, 0);
> + if (!irq_event) {
> + dev_err(&pdev->dev, "IRQ event missing or invalid\n");
> + return -EINVAL;
> + }
> +
> + irq_error = irq_of_parse_and_map(np, 1);
> + if (!irq_error) {
> + dev_err(&pdev->dev, "IRQ error missing or invalid\n");
> + return -EINVAL;
> + }
> +
> + i2c_dev->clk = devm_clk_get(&pdev->dev, NULL);
> + if (IS_ERR(i2c_dev->clk)) {
> + dev_err(&pdev->dev, "Error: Missing controller clock\n");
> + return PTR_ERR(i2c_dev->clk);
> + }
> + ret = clk_prepare_enable(i2c_dev->clk);
> + if (ret) {
> + dev_err(&pdev->dev, "Failed to prepare_enable clock\n");
> + return ret;
> + }
> +
> + rst = devm_reset_control_get(&pdev->dev, NULL);
> + if (IS_ERR(rst)) {
> + dev_err(&pdev->dev, "Error: Missing controller reset\n");
> + ret = PTR_ERR(rst);
> + goto clk_free;
> + }
> + reset_control_assert(rst);
> + udelay(2);
> + reset_control_deassert(rst);
> +
> + i2c_dev->speed = STM32_I2C_SPEED_STANDARD;
> + ret = of_property_read_u32(np, "clock-frequency", &clk_rate);
> + if ((!ret) && (clk_rate == 400000))
> + i2c_dev->speed = STM32_I2C_SPEED_FAST;
> + else if ((!ret) && (clk_rate == 1000000))
> + i2c_dev->speed = STM32_I2C_SPEED_FAST_PLUS;

Did you use an early patch of stm32f4 as cut-n-paste source? Better use:

ret = of_property_read_u32(np, "clock-frequency", &clk_rate);
if (!ret && clk_rate >= 1000000) {
i2c_dev->speed = STM32_I2C_SPEED_FAST_PLUS;
} else if (!ret && clk_rate >= 400000) {
i2c_dev->speed = STM32_I2C_SPEED_FAST;
} else if (!ret && clk_rate >= 100000)
i2c_dev->speed = STM32_I2C_SPEED_STANDARD;
else {
dev_err(..., "Unsupported clock speed\n");
return -EINVAL;
}

and I suggest to do this before touching the hardware, i.e. (at least)
above reset_control_assert().

> + i2c_dev->dev = &pdev->dev;
> +
> + ret = devm_request_irq(&pdev->dev, irq_event, stm32f7_i2c_isr_event, 0,
> + pdev->name, i2c_dev);
> + if (ret) {
> + dev_err(&pdev->dev, "Failed to request irq event %i\n",
> + irq_event);
> + goto clk_free;
> + }
> +
> + ret = devm_request_irq(&pdev->dev, irq_error, stm32f7_i2c_isr_error, 0,
> + pdev->name, i2c_dev);
> + if (ret) {
> + dev_err(&pdev->dev, "Failed to request irq error %i\n",
> + irq_error);
> + goto clk_free;
> + }
> +
> + match = of_match_device(stm32f7_i2c_match, &pdev->dev);
> + if (match && match->data)
> + setup = (struct stm32f7_i2c_setup *)match->data;
> + else
> + goto clk_free;

Why do you use this construct if there is only a single compatible that
is supported? This is open coding of_device_get_match_data, an
additional benefit of using this one is that you don't need
stm32f7_i2c_match here which is a precondition to move this down as
suggested above.

> +
> + ret = device_property_read_u32(i2c_dev->dev, "i2c-scl-rising-time-ns",
> + &rise_time);
> + if (!ret)
> + setup->rise_time = rise_time;
> +
> + ret = device_property_read_u32(i2c_dev->dev, "i2c-scl-falling-time-ns",
> + &fall_time);
> + if (!ret)
> + setup->fall_time = fall_time;
> +
> + ret = stm32f7_i2c_setup_timing(i2c_dev, setup);
> + if (ret)
> + goto clk_free;
> +
> + stm32f7_i2c_hw_config(i2c_dev);
> +
> + adap = &i2c_dev->adap;
> + i2c_set_adapdata(adap, i2c_dev);
> + snprintf(adap->name, sizeof(adap->name), "STM32F7 I2C(%pa)",
> + &res->start);
> + adap->owner = THIS_MODULE;
> + adap->timeout = 2 * HZ;
> + adap->retries = 0;
> + adap->algo = &stm32f7_i2c_algo;
> + adap->dev.parent = &pdev->dev;
> + adap->dev.of_node = pdev->dev.of_node;
> +
> + init_completion(&i2c_dev->complete);
> +
> + ret = i2c_add_adapter(adap);
> + if (ret) {
> + dev_err(&pdev->dev, "Failed to add adapter\n");
> + goto clk_free;
> + }
> +
> + platform_set_drvdata(pdev, i2c_dev);

I'd do this earlier. There is no real problem that is fixed, as the only
user is stm32f7_i2c_remove that is only called when stm32f7_i2c_probe
returns success, but it still feels better. Might be subjective, so
ignore at will.

> + clk_disable(i2c_dev->clk);
> +
> + dev_info(i2c_dev->dev, "STM32F7 I2C-%d driver registered\n", adap->nr);

This is wrong. The driver is already registered via

module_platform_driver(stm32f7_i2c_driver);

below. What you want to claim here is, that the driver bound a device.

> +
> + return 0;
> +
> +clk_free:
> + clk_disable_unprepare(i2c_dev->clk);
> +
> + return ret;
> +}
> +
> +static int stm32f7_i2c_remove(struct platform_device *pdev)
> +{
> + struct stm32f7_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
> +
> + i2c_del_adapter(&i2c_dev->adap);
> +
> + clk_unprepare(i2c_dev->clk);
> +
> + return 0;
> +}
> +
> +static struct platform_driver stm32f7_i2c_driver = {
> + .driver = {
> + .name = "stm32f7-i2c",
> + .of_match_table = stm32f7_i2c_match,
> + },
> + .probe = stm32f7_i2c_probe,
> + .remove = stm32f7_i2c_remove,
> +};
> +
> +module_platform_driver(stm32f7_i2c_driver);
> +
> +MODULE_AUTHOR("M'boumba Cedric Madianga <cedric.madianga@xxxxxxxxx>");
> +MODULE_DESCRIPTION("STMicroelectronics STM32F7 I2C driver");
> +MODULE_LICENSE("GPL v2");

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

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