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Subject: Re: [PATCH 4/6] i2c: i2c-stm32f7: add PM_SLEEP suspend/resume support
To:     Alain Volmat <alain.volmat@st.com>, <wsa@the-dreams.de>,
        <robh+dt@kernel.org>
CC:     <mark.rutland@arm.com>, <mcoquelin.stm32@gmail.com>,
        <alexandre.torgue@st.com>, <linux-i2c@vger.kernel.org>,
        <devicetree@vger.kernel.org>,
        <linux-stm32@st-md-mailman.stormreply.com>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>, <fabrice.gasnier@st.com>
References: <1578317314-17197-1-git-send-email-alain.volmat@st.com>
 <1578317314-17197-5-git-send-email-alain.volmat@st.com>
From:   Pierre Yves MORDRET <pierre-yves.mordret@st.com>
Message-ID: <5f930987-2a15-3a82-654d-2db8fd528876@st.com>
Date:   Wed, 15 Jan 2020 10:13:19 +0100
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Hi all,

Reviewed-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>

Regards

On 1/6/20 2:28 PM, Alain Volmat wrote:
> Backup/restore I2C registers as part of the suspend/resume
> handlers. The device is marked as suspended to ensure that
> transfers are rejected during the suspended period.
> 
> Signed-off-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
> Signed-off-by: Alain Volmat <alain.volmat@st.com>
> ---
>  drivers/i2c/busses/i2c-stm32f7.c | 117 +++++++++++++++++++++++++++++++++++++--
>  1 file changed, 113 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
> index b2634afe066d..5c3e8ac6ad92 100644
> --- a/drivers/i2c/busses/i2c-stm32f7.c
> +++ b/drivers/i2c/busses/i2c-stm32f7.c
> @@ -169,6 +169,24 @@
>  #define STM32F7_AUTOSUSPEND_DELAY		(HZ / 100)
>  
>  /**
> + * struct stm32f7_i2c_regs - i2c f7 registers backup
> + * @cr1: Control register 1
> + * @cr2: Control register 2
> + * @oar1: Own address 1 register
> + * @oar2: Own address 2 register
> + * @pecr: PEC register
> + * @tmgr: Timing register
> + */
> +struct stm32f7_i2c_regs {
> +	u32 cr1;
> +	u32 cr2;
> +	u32 oar1;
> +	u32 oar2;
> +	u32 pecr;
> +	u32 tmgr;
> +};
> +
> +/**
>   * struct stm32f7_i2c_spec - private i2c specification timing
>   * @rate: I2C bus speed (Hz)
>   * @rate_min: 80% of I2C bus speed (Hz)
> @@ -276,6 +294,7 @@ struct stm32f7_i2c_msg {
>   * @timing: I2C computed timings
>   * @slave: list of slave devices registered on the I2C bus
>   * @slave_running: slave device currently used
> + * @backup_regs: backup of i2c controller registers (for suspend/resume)
>   * @slave_dir: transfer direction for the current slave device
>   * @master_mode: boolean to know in which mode the I2C is running (master or
>   * slave)
> @@ -298,6 +317,7 @@ struct stm32f7_i2c_dev {
>  	struct stm32f7_i2c_timings timing;
>  	struct i2c_client *slave[STM32F7_I2C_MAX_SLAVE];
>  	struct i2c_client *slave_running;
> +	struct stm32f7_i2c_regs backup_regs;
>  	u32 slave_dir;
>  	bool master_mode;
>  	struct stm32_i2c_dma *dma;
> @@ -2027,8 +2047,7 @@ static int stm32f7_i2c_remove(struct platform_device *pdev)
>  	return 0;
>  }
>  
> -#ifdef CONFIG_PM
> -static int stm32f7_i2c_runtime_suspend(struct device *dev)
> +static int __maybe_unused stm32f7_i2c_runtime_suspend(struct device *dev)
>  {
>  	struct stm32f7_i2c_dev *i2c_dev = dev_get_drvdata(dev);
>  
> @@ -2038,7 +2057,7 @@ static int stm32f7_i2c_runtime_suspend(struct device *dev)
>  	return 0;
>  }
>  
> -static int stm32f7_i2c_runtime_resume(struct device *dev)
> +static int __maybe_unused stm32f7_i2c_runtime_resume(struct device *dev)
>  {
>  	struct stm32f7_i2c_dev *i2c_dev = dev_get_drvdata(dev);
>  	int ret;
> @@ -2053,11 +2072,101 @@ static int stm32f7_i2c_runtime_resume(struct device *dev)
>  
>  	return 0;
>  }
> -#endif
> +
> +static int __maybe_unused
> +stm32f7_i2c_regs_backup(struct stm32f7_i2c_dev *i2c_dev)
> +{
> +	int ret;
> +	struct stm32f7_i2c_regs *backup_regs = &i2c_dev->backup_regs;
> +
> +	ret = pm_runtime_get_sync(i2c_dev->dev);
> +	if (ret < 0)
> +		return ret;
> +
> +	backup_regs->cr1 = readl_relaxed(i2c_dev->base + STM32F7_I2C_CR1);
> +	backup_regs->cr2 = readl_relaxed(i2c_dev->base + STM32F7_I2C_CR2);
> +	backup_regs->oar1 = readl_relaxed(i2c_dev->base + STM32F7_I2C_OAR1);
> +	backup_regs->oar2 = readl_relaxed(i2c_dev->base + STM32F7_I2C_OAR2);
> +	backup_regs->pecr = readl_relaxed(i2c_dev->base + STM32F7_I2C_PECR);
> +	backup_regs->tmgr = readl_relaxed(i2c_dev->base + STM32F7_I2C_TIMINGR);
> +
> +	pm_runtime_put_sync(i2c_dev->dev);
> +
> +	return ret;
> +}
> +
> +static int __maybe_unused
> +stm32f7_i2c_regs_restore(struct stm32f7_i2c_dev *i2c_dev)
> +{
> +	u32 cr1;
> +	int ret;
> +	struct stm32f7_i2c_regs *backup_regs = &i2c_dev->backup_regs;
> +
> +	ret = pm_runtime_get_sync(i2c_dev->dev);
> +	if (ret < 0)
> +		return ret;
> +
> +	cr1 = readl_relaxed(i2c_dev->base + STM32F7_I2C_CR1);
> +	if (cr1 & STM32F7_I2C_CR1_PE)
> +		stm32f7_i2c_clr_bits(i2c_dev->base + STM32F7_I2C_CR1,
> +				     STM32F7_I2C_CR1_PE);
> +
> +	writel_relaxed(backup_regs->tmgr, i2c_dev->base + STM32F7_I2C_TIMINGR);
> +	writel_relaxed(backup_regs->cr1 & ~STM32F7_I2C_CR1_PE,
> +		       i2c_dev->base + STM32F7_I2C_CR1);
> +	if (backup_regs->cr1 & STM32F7_I2C_CR1_PE)
> +		stm32f7_i2c_set_bits(i2c_dev->base + STM32F7_I2C_CR1,
> +				     STM32F7_I2C_CR1_PE);
> +	writel_relaxed(backup_regs->cr2, i2c_dev->base + STM32F7_I2C_CR2);
> +	writel_relaxed(backup_regs->oar1, i2c_dev->base + STM32F7_I2C_OAR1);
> +	writel_relaxed(backup_regs->oar2, i2c_dev->base + STM32F7_I2C_OAR2);
> +	writel_relaxed(backup_regs->pecr, i2c_dev->base + STM32F7_I2C_PECR);
> +
> +	pm_runtime_put_sync(i2c_dev->dev);
> +
> +	return ret;
> +}
> +
> +static int __maybe_unused stm32f7_i2c_suspend(struct device *dev)
> +{
> +	struct stm32f7_i2c_dev *i2c_dev = dev_get_drvdata(dev);
> +	int ret;
> +
> +	i2c_mark_adapter_suspended(&i2c_dev->adap);
> +	ret = stm32f7_i2c_regs_backup(i2c_dev);
> +	if (ret < 0) {
> +		i2c_mark_adapter_resumed(&i2c_dev->adap);
> +		return ret;
> +	}
> +
> +	pinctrl_pm_select_sleep_state(dev);
> +	pm_runtime_force_suspend(dev);
> +
> +	return 0;
> +}
> +
> +static int __maybe_unused stm32f7_i2c_resume(struct device *dev)
> +{
> +	struct stm32f7_i2c_dev *i2c_dev = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = pm_runtime_force_resume(dev);
> +	if (ret < 0)
> +		return ret;
> +	pinctrl_pm_select_default_state(dev);
> +
> +	ret = stm32f7_i2c_regs_restore(i2c_dev);
> +	if (ret < 0)
> +		return ret;
> +	i2c_mark_adapter_resumed(&i2c_dev->adap);
> +
> +	return 0;
> +}
>  
>  static const struct dev_pm_ops stm32f7_i2c_pm_ops = {
>  	SET_RUNTIME_PM_OPS(stm32f7_i2c_runtime_suspend,
>  			   stm32f7_i2c_runtime_resume, NULL)
> +	SET_SYSTEM_SLEEP_PM_OPS(stm32f7_i2c_suspend, stm32f7_i2c_resume)
>  };
>  
>  static const struct of_device_id stm32f7_i2c_match[] = {
>