Date:   Fri, 13 Nov 2020 14:59:47 +0100
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     Biwen Li <biwen.li@....nxp.com>
Cc:     leoyang.li@....com, linux@...pel-privat.de, kernel@...gutronix.de,
        wsa@...-dreams.de, shawnguo@...nel.org, s.hauer@...gutronix.de,
        festevam@...il.com, aisheng.dong@....com, xiaoning.wang@....com,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        jiafei.pan@....com, xiaobo.xie@....com,
        linux-arm-kernel@...ts.infradead.org, Biwen Li <biwen.li@....com>
Subject: Re: [v10] i2c: imx: support slave mode for imx I2C driver

On Wed, Nov 11, 2020 at 07:32:55PM +0800, Biwen Li wrote:
> From: Biwen Li <biwen.li@....com>
> 
> The patch supports slave mode for imx I2C driver
> 
> Signed-off-by: Biwen Li <biwen.li@....com>

Thank you for your work!

Acked-by: Oleksij Rempel <o.rempel@...gutronix.de>

@Wolfram, Christian Eggers I2SR_IAL patches should go before this one.

> ---
> Change in v10:
> 	- totally remove CONFIG_I2C_SLAVE
> 	- replace api with i2c_imx_clart_irq()
> 	- remove robust code
> 	- place pm_runtime_get in i2c_imx_slave_init()
> 	  to i2c_imx_reg_slave()
> 	- apply the patch on top of this patch set:
> 	  [PATCH v6 0/3] i2c: imx: Fix handling of arbitration loss
> 	  https://lkml.org/lkml/2020/10/9/407
> 
> Change in v9:
> 	- remove #ifdef after select I2C_SLAVE by default
> 
> Change in v8:
> 	- fix build issue
> 
> Change in v7:
> 	- support auto switch mode between master and slave
> 	- enable interrupt when idle in slave mode
> 	- remove #ifdef
> 
> Change in v6:
> 	- delete robust logs and comments
> 	- not read status register again in master isr.
> 
> Change in v5:
> 	- fix a bug that cannot determine in what mode(master mode or
> 	  slave mode)
> 
> Change in v4:
> 	- add MACRO CONFIG_I2C_SLAVE to fix compilation issue
> 
> Change in v3:
> 	- support layerscape and i.mx platform
> 
> Change in v2:
> 	- remove MACRO CONFIG_I2C_SLAVE
> 
>  drivers/i2c/busses/Kconfig   |   1 +
>  drivers/i2c/busses/i2c-imx.c | 219 +++++++++++++++++++++++++++++++----
>  2 files changed, 196 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index a97a9d058198..e2ad62481f25 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -675,6 +675,7 @@ config I2C_IMG
>  config I2C_IMX
>  	tristate "IMX I2C interface"
>  	depends on ARCH_MXC || ARCH_LAYERSCAPE || COLDFIRE
> +	select I2C_SLAVE
>  	help
>  	  Say Y here if you want to use the IIC bus controller on
>  	  the Freescale i.MX/MXC, Layerscape or ColdFire processors.
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index e6f8d6e45a15..a8e8af57e33f 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -17,6 +17,7 @@
>   *	Copyright (C) 2008 Darius Augulis <darius.augulis at teltonika.lt>
>   *
>   *	Copyright 2013 Freescale Semiconductor, Inc.
> + *	Copyright 2020 NXP
>   *
>   */
>  
> @@ -73,6 +74,11 @@
>  #define IMX_I2C_I2SR	0x03	/* i2c status */
>  #define IMX_I2C_I2DR	0x04	/* i2c transfer data */
>  
> +/*
> + * All of the layerscape series SoCs support IBIC register.
> + */
> +#define IMX_I2C_IBIC	0x05    /* i2c bus interrupt config */
> +
>  #define IMX_I2C_REGSHIFT	2
>  #define VF610_I2C_REGSHIFT	0
>  
> @@ -91,6 +97,7 @@
>  #define I2CR_MSTA	0x20
>  #define I2CR_IIEN	0x40
>  #define I2CR_IEN	0x80
> +#define IBIC_BIIE	0x80 /* Bus idle interrupt enable */
>  
>  /* register bits different operating codes definition:
>   * 1) I2SR: Interrupt flags clear operation differ between SoCs:
> @@ -201,6 +208,7 @@ struct imx_i2c_struct {
>  	struct pinctrl_state *pinctrl_pins_gpio;
>  
>  	struct imx_i2c_dma	*dma;
> +	struct i2c_client	*slave;
>  };
>  
>  static const struct imx_i2c_hwdata imx1_i2c_hwdata = {
> @@ -265,6 +273,11 @@ static inline int is_imx1_i2c(struct imx_i2c_struct *i2c_imx)
>  	return i2c_imx->hwdata->devtype == IMX1_I2C;
>  }
>  
> +static inline int is_vf610_i2c(struct imx_i2c_struct *i2c_imx)
> +{
> +	return i2c_imx->hwdata->devtype == VF610_I2C;
> +}
> +
>  static inline void imx_i2c_write_reg(unsigned int val,
>  		struct imx_i2c_struct *i2c_imx, unsigned int reg)
>  {
> @@ -277,6 +290,27 @@ static inline unsigned char imx_i2c_read_reg(struct imx_i2c_struct *i2c_imx,
>  	return readb(i2c_imx->base + (reg << i2c_imx->hwdata->regshift));
>  }
>  
> +static void i2c_imx_clear_irq(struct imx_i2c_struct *i2c_imx, unsigned int bits)
> +{
> +	unsigned int temp;
> +
> +	/*
> +	 * i2sr_clr_opcode is the value to clear all interrupts. Here we want to
> +	 * clear only <bits>, so we write ~i2sr_clr_opcode with just <bits>
> +	 * toggled. This is required because i.MX needs W0C and Vybrid uses W1C.
> +	 */
> +	temp = ~i2c_imx->hwdata->i2sr_clr_opcode ^ bits;
> +	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2SR);
> +}
> +
> +/* Set up i2c controller register and i2c status register to default value. */
> +static void i2c_imx_reset_regs(struct imx_i2c_struct *i2c_imx)
> +{
> +	imx_i2c_write_reg(i2c_imx->hwdata->i2cr_ien_opcode ^ I2CR_IEN,
> +			  i2c_imx, IMX_I2C_I2CR);
> +	i2c_imx_clear_irq(i2c_imx, I2SR_IIF | I2SR_IAL);
> +}
> +
>  /* Functions for DMA support */
>  static void i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
>  						dma_addr_t phy_addr)
> @@ -412,19 +446,6 @@ static void i2c_imx_dma_free(struct imx_i2c_struct *i2c_imx)
>  	dma->chan_using = NULL;
>  }
>  
> -static void i2c_imx_clear_irq(struct imx_i2c_struct *i2c_imx, unsigned int bits)
> -{
> -	unsigned int temp;
> -
> -	/*
> -	 * i2sr_clr_opcode is the value to clear all interrupts. Here we want to
> -	 * clear only <bits>, so we write ~i2sr_clr_opcode with just <bits>
> -	 * toggled. This is required because i.MX needs W0C and Vybrid uses W1C.
> -	 */
> -	temp = ~i2c_imx->hwdata->i2sr_clr_opcode ^ bits;
> -	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2SR);
> -}
> -
>  static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx, int for_busy, bool atomic)
>  {
>  	unsigned long orig_jiffies = jiffies;
> @@ -638,18 +659,165 @@ static void i2c_imx_stop(struct imx_i2c_struct *i2c_imx, bool atomic)
>  	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
>  }
>  
> +/*
> + * Enable bus idle interrupts
> + * Note: IBIC register will be cleared after disabled i2c module.
> + * All of layerscape series SoCs support IBIC register.
> + */
> +static void i2c_imx_enable_bus_idle(struct imx_i2c_struct *i2c_imx)
> +{
> +	if (is_vf610_i2c(i2c_imx)) {
> +		unsigned int temp;
> +
> +		temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_IBIC);
> +		temp |= IBIC_BIIE;
> +		imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_IBIC);
> +	}
> +}
> +
> +static irqreturn_t i2c_imx_slave_isr(struct imx_i2c_struct *i2c_imx,
> +				     unsigned int status, unsigned int ctl)
> +{
> +	u8 value;
> +
> +	if (status & I2SR_IAL) { /* Arbitration lost */
> +		i2c_imx_clear_irq(i2c_imx, I2SR_IAL);
> +		if (!(status & I2SR_IAAS))
> +			return IRQ_HANDLED;
> +	}
> +
> +	if (status & I2SR_IAAS) { /* Addressed as a slave */
> +		if (status & I2SR_SRW) { /* Master wants to read from us*/
> +			dev_dbg(&i2c_imx->adapter.dev, "read requested");
> +			i2c_slave_event(i2c_imx->slave, I2C_SLAVE_READ_REQUESTED, &value);
> +
> +			/* Slave transmit */
> +			ctl |= I2CR_MTX;
> +			imx_i2c_write_reg(ctl, i2c_imx, IMX_I2C_I2CR);
> +
> +			/* Send data */
> +			imx_i2c_write_reg(value, i2c_imx, IMX_I2C_I2DR);
> +		} else { /* Master wants to write to us */
> +			dev_dbg(&i2c_imx->adapter.dev, "write requested");
> +			i2c_slave_event(i2c_imx->slave,	I2C_SLAVE_WRITE_REQUESTED, &value);
> +
> +			/* Slave receive */
> +			ctl &= ~I2CR_MTX;
> +			imx_i2c_write_reg(ctl, i2c_imx, IMX_I2C_I2CR);
> +			/* Dummy read */
> +			imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
> +		}
> +	} else if (!(ctl & I2CR_MTX)) { /* Receive mode */
> +		if (status & I2SR_IBB) { /* No STOP signal detected */
> +			value = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
> +			i2c_slave_event(i2c_imx->slave,	I2C_SLAVE_WRITE_RECEIVED, &value);
> +		} else { /* STOP signal is detected */
> +			dev_dbg(&i2c_imx->adapter.dev,
> +				"STOP signal detected");
> +			i2c_slave_event(i2c_imx->slave, I2C_SLAVE_STOP, &value);
> +		}
> +	} else if (!(status & I2SR_RXAK)) { /* Transmit mode received ACK */
> +		ctl |= I2CR_MTX;
> +		imx_i2c_write_reg(ctl, i2c_imx, IMX_I2C_I2CR);
> +
> +		i2c_slave_event(i2c_imx->slave,	I2C_SLAVE_READ_PROCESSED, &value);
> +
> +		imx_i2c_write_reg(value, i2c_imx, IMX_I2C_I2DR);
> +	} else { /* Transmit mode received NAK */
> +		ctl &= ~I2CR_MTX;
> +		imx_i2c_write_reg(ctl, i2c_imx, IMX_I2C_I2CR);
> +		imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
> +	}
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static void i2c_imx_slave_init(struct imx_i2c_struct *i2c_imx)
> +{
> +	int temp;
> +
> +	/* Set slave addr. */
> +	imx_i2c_write_reg((i2c_imx->slave->addr << 1), i2c_imx, IMX_I2C_IADR);
> +
> +	i2c_imx_reset_regs(i2c_imx);
> +
> +	/* Enable module */
> +	temp = i2c_imx->hwdata->i2cr_ien_opcode;
> +	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
> +
> +	/* Enable interrupt from i2c module */
> +	temp |= I2CR_IIEN;
> +	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
> +
> +	i2c_imx_enable_bus_idle(i2c_imx);
> +}
> +
> +static int i2c_imx_reg_slave(struct i2c_client *client)
> +{
> +	struct imx_i2c_struct *i2c_imx = i2c_get_adapdata(client->adapter);
> +	int ret;
> +
> +	if (i2c_imx->slave)
> +		return -EBUSY;
> +
> +	i2c_imx->slave = client;
> +
> +	/* Resume */
> +	ret = pm_runtime_get_sync(i2c_imx->adapter.dev.parent);
> +	if (ret < 0) {
> +		dev_err(&i2c_imx->adapter.dev, "failed to resume i2c controller");
> +		return ret;
> +	}
> +
> +	i2c_imx_slave_init(i2c_imx);
> +
> +	return 0;
> +}
> +
> +static int i2c_imx_unreg_slave(struct i2c_client *client)
> +{
> +	struct imx_i2c_struct *i2c_imx = i2c_get_adapdata(client->adapter);
> +	int ret;
> +
> +	if (!i2c_imx->slave)
> +		return -EINVAL;
> +
> +	/* Reset slave address. */
> +	imx_i2c_write_reg(0, i2c_imx, IMX_I2C_IADR);
> +
> +	i2c_imx_reset_regs(i2c_imx);
> +
> +	i2c_imx->slave = NULL;
> +
> +	/* Suspend */
> +	ret = pm_runtime_put_sync(i2c_imx->adapter.dev.parent);
> +	if (ret < 0)
> +		dev_err(&i2c_imx->adapter.dev, "failed to suspend i2c controller");
> +
> +	return ret;
> +}
> +
> +static irqreturn_t i2c_imx_master_isr(struct imx_i2c_struct *i2c_imx, unsigned int status)
> +{
> +	/* save status register */
> +	i2c_imx->i2csr = status;
> +	wake_up(&i2c_imx->queue);
> +
> +	return IRQ_HANDLED;
> +}
> +
>  static irqreturn_t i2c_imx_isr(int irq, void *dev_id)
>  {
>  	struct imx_i2c_struct *i2c_imx = dev_id;
> -	unsigned int temp;
> +	unsigned int ctl, status;
>  
> -	temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
> -	if (temp & I2SR_IIF) {
> -		/* save status register */
> -		i2c_imx->i2csr = temp;
> +	status = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
> +	ctl = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
> +	if (status & I2SR_IIF) {
>  		i2c_imx_clear_irq(i2c_imx, I2SR_IIF);
> -		wake_up(&i2c_imx->queue);
> -		return IRQ_HANDLED;
> +		if (i2c_imx->slave && !(ctl & I2CR_MSTA))
> +			return i2c_imx_slave_isr(i2c_imx, status, ctl);
> +		return i2c_imx_master_isr(i2c_imx, status);
>  	}
>  
>  	return IRQ_NONE;
> @@ -1027,6 +1195,10 @@ static int i2c_imx_xfer_common(struct i2c_adapter *adapter,
>  	dev_dbg(&i2c_imx->adapter.dev, "<%s> exit with: %s: %d\n", __func__,
>  		(result < 0) ? "error" : "success msg",
>  			(result < 0) ? result : num);
> +	/* After data is transferred, switch to slave mode(as a receiver) */
> +	if (i2c_imx->slave)
> +		i2c_imx_slave_init(i2c_imx);
> +
>  	return (result < 0) ? result : num;
>  }
>  
> @@ -1140,6 +1312,8 @@ static const struct i2c_algorithm i2c_imx_algo = {
>  	.master_xfer = i2c_imx_xfer,
>  	.master_xfer_atomic = i2c_imx_xfer_atomic,
>  	.functionality = i2c_imx_func,
> +	.reg_slave	= i2c_imx_reg_slave,
> +	.unreg_slave	= i2c_imx_unreg_slave,
>  };
>  
>  static int i2c_imx_probe(struct platform_device *pdev)
> @@ -1233,10 +1407,7 @@ static int i2c_imx_probe(struct platform_device *pdev)
>  	clk_notifier_register(i2c_imx->clk, &i2c_imx->clk_change_nb);
>  	i2c_imx_set_clk(i2c_imx, clk_get_rate(i2c_imx->clk));
>  
> -	/* Set up chip registers to defaults */
> -	imx_i2c_write_reg(i2c_imx->hwdata->i2cr_ien_opcode ^ I2CR_IEN,
> -			i2c_imx, IMX_I2C_I2CR);
> -	imx_i2c_write_reg(i2c_imx->hwdata->i2sr_clr_opcode, i2c_imx, IMX_I2C_I2SR);
> +	i2c_imx_reset_regs(i2c_imx);
>  
>  	/* Init optional bus recovery function */
>  	ret = i2c_imx_init_recovery_info(i2c_imx, pdev);
> -- 
> 2.17.1
> 
> 

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