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Subject: Re: [PATCH] i2c: meson: implement the master_xfer_atomic callback
To:     Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
        linux-i2c@vger.kernel.org, linux-amlogic@lists.infradead.org,
        wsa@the-dreams.de
Cc:     khilman@baylibre.com, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, b.galvani@gmail.com,
        jian.hu@amlogic.com
References: <20200107232901.891177-1-martin.blumenstingl@googlemail.com>
From:   Neil Armstrong <narmstrong@baylibre.com>
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Organization: Baylibre
Message-ID: <b516a6aa-f1b9-1e01-916e-7fd582f9a6e5@baylibre.com>
Date:   Wed, 8 Jan 2020 14:03:48 +0100
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On 08/01/2020 00:29, Martin Blumenstingl wrote:
> Boards with some of the 32-bit SoCs (mostly Meson8 and Meson8m2) use a
> Ricoh RN5T618 PMU which acts as system power controller. The driver for
> the system power controller may need to the I2C bus just before shutting
> down or rebooting the system. At this stage the interrupts may be
> disabled already.
> 
> Implement the master_xfer_atomic callback so the driver for the RN5T618
> PMU can communicate properly with the PMU when shutting down or
> rebooting the board. The CTRL register has a status bit which can be
> polled to determine when processing has completed. According to the
> public S805 datasheet the value 0 means "idle" and 1 means "running".
> 
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> ---
>  drivers/i2c/busses/i2c-meson.c | 97 +++++++++++++++++++++++-----------
>  1 file changed, 65 insertions(+), 32 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-meson.c b/drivers/i2c/busses/i2c-meson.c
> index 1e2647f9a2a7..7486b46e475f 100644
> --- a/drivers/i2c/busses/i2c-meson.c
> +++ b/drivers/i2c/busses/i2c-meson.c
> @@ -10,6 +10,7 @@
>  #include <linux/i2c.h>
>  #include <linux/interrupt.h>
>  #include <linux/io.h>
> +#include <linux/iopoll.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> @@ -213,6 +214,30 @@ static void meson_i2c_prepare_xfer(struct meson_i2c *i2c)
>  	writel(i2c->tokens[1], i2c->regs + REG_TOK_LIST1);
>  }
>  
> +static void meson_i2c_transfer_complete(struct meson_i2c *i2c, u32 ctrl)
> +{
> +	if (ctrl & REG_CTRL_ERROR) {
> +		/*
> +		 * The bit is set when the IGNORE_NAK bit is cleared
> +		 * and the device didn't respond. In this case, the
> +		 * I2C controller automatically generates a STOP
> +		 * condition.
> +		 */
> +		dev_dbg(i2c->dev, "error bit set\n");
> +		i2c->error = -ENXIO;
> +		i2c->state = STATE_IDLE;
> +	} else {
> +		if (i2c->state == STATE_READ && i2c->count)
> +			meson_i2c_get_data(i2c, i2c->msg->buf + i2c->pos,
> +					   i2c->count);
> +
> +		i2c->pos += i2c->count;
> +
> +		if (i2c->pos >= i2c->msg->len)
> +			i2c->state = STATE_IDLE;
> +	}
> +}
> +
>  static irqreturn_t meson_i2c_irq(int irqno, void *dev_id)
>  {
>  	struct meson_i2c *i2c = dev_id;
> @@ -232,27 +257,9 @@ static irqreturn_t meson_i2c_irq(int irqno, void *dev_id)
>  		return IRQ_NONE;
>  	}
>  
> -	if (ctrl & REG_CTRL_ERROR) {
> -		/*
> -		 * The bit is set when the IGNORE_NAK bit is cleared
> -		 * and the device didn't respond. In this case, the
> -		 * I2C controller automatically generates a STOP
> -		 * condition.
> -		 */
> -		dev_dbg(i2c->dev, "error bit set\n");
> -		i2c->error = -ENXIO;
> -		i2c->state = STATE_IDLE;
> -		complete(&i2c->done);
> -		goto out;
> -	}
> -
> -	if (i2c->state == STATE_READ && i2c->count)
> -		meson_i2c_get_data(i2c, i2c->msg->buf + i2c->pos, i2c->count);
> +	meson_i2c_transfer_complete(i2c, ctrl);
>  
> -	i2c->pos += i2c->count;
> -
> -	if (i2c->pos >= i2c->msg->len) {
> -		i2c->state = STATE_IDLE;
> +	if (i2c->state == STATE_IDLE) {
>  		complete(&i2c->done);
>  		goto out;
>  	}
> @@ -279,10 +286,11 @@ static void meson_i2c_do_start(struct meson_i2c *i2c, struct i2c_msg *msg)
>  }
>  
>  static int meson_i2c_xfer_msg(struct meson_i2c *i2c, struct i2c_msg *msg,
> -			      int last)
> +			      int last, bool atomic)
>  {
>  	unsigned long time_left, flags;
>  	int ret = 0;
> +	u32 ctrl;
>  
>  	i2c->msg = msg;
>  	i2c->last = last;
> @@ -300,13 +308,24 @@ static int meson_i2c_xfer_msg(struct meson_i2c *i2c, struct i2c_msg *msg,
>  
>  	i2c->state = (msg->flags & I2C_M_RD) ? STATE_READ : STATE_WRITE;
>  	meson_i2c_prepare_xfer(i2c);
> -	reinit_completion(&i2c->done);
> +
> +	if (!atomic)
> +		reinit_completion(&i2c->done);
>  
>  	/* Start the transfer */
>  	meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, REG_CTRL_START);
>  
> -	time_left = msecs_to_jiffies(I2C_TIMEOUT_MS);
> -	time_left = wait_for_completion_timeout(&i2c->done, time_left);
> +	if (atomic) {
> +		ret = readl_poll_timeout_atomic(i2c->regs + REG_CTRL, ctrl,
> +						!(ctrl & REG_CTRL_STATUS),
> +						10, I2C_TIMEOUT_MS * 1000);
> +	} else {
> +		time_left = msecs_to_jiffies(I2C_TIMEOUT_MS);
> +		time_left = wait_for_completion_timeout(&i2c->done, time_left);
> +
> +		if (!time_left)
> +			ret = -ETIMEDOUT;
> +	}
>  
>  	/*
>  	 * Protect access to i2c struct and registers from interrupt
> @@ -315,13 +334,14 @@ static int meson_i2c_xfer_msg(struct meson_i2c *i2c, struct i2c_msg *msg,
>  	 */
>  	spin_lock_irqsave(&i2c->lock, flags);
>  
> +	if (atomic && !ret)
> +		meson_i2c_transfer_complete(i2c, ctrl);
> +
>  	/* Abort any active operation */
>  	meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, 0);
>  
> -	if (!time_left) {
> +	if (ret)
>  		i2c->state = STATE_IDLE;
> -		ret = -ETIMEDOUT;
> -	}
>  
>  	if (i2c->error)
>  		ret = i2c->error;
> @@ -331,8 +351,8 @@ static int meson_i2c_xfer_msg(struct meson_i2c *i2c, struct i2c_msg *msg,
>  	return ret;
>  }
>  
> -static int meson_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> -			  int num)
> +static int meson_i2c_xfer_messages(struct i2c_adapter *adap,
> +				   struct i2c_msg *msgs, int num, bool atomic)
>  {
>  	struct meson_i2c *i2c = adap->algo_data;
>  	int i, ret = 0;
> @@ -340,7 +360,7 @@ static int meson_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
>  	clk_enable(i2c->clk);
>  
>  	for (i = 0; i < num; i++) {
> -		ret = meson_i2c_xfer_msg(i2c, msgs + i, i == num - 1);
> +		ret = meson_i2c_xfer_msg(i2c, msgs + i, i == num - 1, atomic);
>  		if (ret)
>  			break;
>  	}
> @@ -350,14 +370,27 @@ static int meson_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
>  	return ret ?: i;
>  }
>  
> +static int meson_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> +			  int num)
> +{
> +	return meson_i2c_xfer_messages(adap, msgs, num, false);
> +}
> +
> +static int meson_i2c_xfer_atomic(struct i2c_adapter *adap,
> +				 struct i2c_msg *msgs, int num)
> +{
> +	return meson_i2c_xfer_messages(adap, msgs, num, true);
> +}
> +
>  static u32 meson_i2c_func(struct i2c_adapter *adap)
>  {
>  	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
>  }
>  
>  static const struct i2c_algorithm meson_i2c_algorithm = {
> -	.master_xfer	= meson_i2c_xfer,
> -	.functionality	= meson_i2c_func,
> +	.master_xfer		= meson_i2c_xfer,
> +	.master_xfer_atomic	= meson_i2c_xfer_atomic,
> +	.functionality		= meson_i2c_func,
>  };
>  
>  static int meson_i2c_probe(struct platform_device *pdev)
> 

Looks fine

Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>

Neil