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Commit e2474541 authored by Noralf Trønnes's avatar Noralf Trønnes Committed by Wolfram Sang
Browse files

i2c: bcm2835: Fix hang for writing messages larger than 16 bytes 



Writing messages larger than the FIFO size results in a hang, rendering
the machine unusable. This is because the RXD status flag is set on the
first interrupt which results in bcm2835_drain_rxfifo() stealing bytes
from the buffer. The controller continues to trigger interrupts waiting
for the missing bytes, but bcm2835_fill_txfifo() has none to give.
In this situation wait_for_completion_timeout() apparently is unable to
stop the madness.

The BCM2835 ARM Peripherals datasheet has this to say about the flags:
  TXD: is set when the FIFO has space for at least one byte of data.
  RXD: is set when the FIFO contains at least one byte of data.
  TXW: is set during a write transfer and the FIFO is less than full.
  RXR: is set during a read transfer and the FIFO is or more full.

Implementing the logic from the downstream i2c-bcm2708 driver solved
the hang problem.

Signed-off-by: default avatarNoralf Trønnes <noralf@tronnes.org>
Reviewed-by: default avatarEric Anholt <eric@anholt.net>
Reviewed-by: default avatarMartin Sperl <kernel@martin.sperl.org>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent bc33b0ca

drivers/i2c/busses/i2c-bcm2835.c

+14 −8
Original line number Original line Diff line number Diff line
@@ -64,6 +64,7 @@ struct bcm2835_i2c_dev { 
	int irq;

	int irq;

	struct i2c_adapter adapter;

	struct i2c_adapter adapter;

	struct completion completion;

	struct completion completion;

	struct i2c_msg *curr_msg;

	u32 msg_err;

	u32 msg_err;

	u8 *msg_buf;

	u8 *msg_buf;

	size_t msg_buf_remaining;

	size_t msg_buf_remaining;
@@ -126,14 +127,13 @@ static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data) 
		return IRQ_HANDLED;

		return IRQ_HANDLED;

	}

	}





	if (val & BCM2835_I2C_S_RXD) {

	if (val & BCM2835_I2C_S_DONE) {

		if (i2c_dev->curr_msg->flags & I2C_M_RD) {

			bcm2835_drain_rxfifo(i2c_dev);

			bcm2835_drain_rxfifo(i2c_dev);

		if (!(val & BCM2835_I2C_S_DONE))

			val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);

			return IRQ_HANDLED;

		}

		}





	if (val & BCM2835_I2C_S_DONE) {

		if ((val & BCM2835_I2C_S_RXD) || i2c_dev->msg_buf_remaining)

		if (i2c_dev->msg_buf_remaining)

			i2c_dev->msg_err = BCM2835_I2C_S_LEN;

			i2c_dev->msg_err = BCM2835_I2C_S_LEN;

		else

		else

			i2c_dev->msg_err = 0;

			i2c_dev->msg_err = 0;
@@ -141,11 +141,16 @@ static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data) 
		return IRQ_HANDLED;

		return IRQ_HANDLED;

	}

	}





	if (val & BCM2835_I2C_S_TXD) {

	if (val & BCM2835_I2C_S_TXW) {

		bcm2835_fill_txfifo(i2c_dev);

		bcm2835_fill_txfifo(i2c_dev);

		return IRQ_HANDLED;

		return IRQ_HANDLED;

	}

	}





	if (val & BCM2835_I2C_S_RXR) {

		bcm2835_drain_rxfifo(i2c_dev);

		return IRQ_HANDLED;

	}



	return IRQ_NONE;

	return IRQ_NONE;

}

}
@@ -155,6 +160,7 @@ static int bcm2835_i2c_xfer_msg(struct bcm2835_i2c_dev *i2c_dev, 
	u32 c;

	u32 c;

	unsigned long time_left;

	unsigned long time_left;





	i2c_dev->curr_msg = msg;

	i2c_dev->msg_buf = msg->buf;

	i2c_dev->msg_buf = msg->buf;

	i2c_dev->msg_buf_remaining = msg->len;

	i2c_dev->msg_buf_remaining = msg->len;

	reinit_completion(&i2c_dev->completion);

	reinit_completion(&i2c_dev->completion);