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: Noralf Trønnes <noralf@tronnes.org> Reviewed-by: Eric Anholt <eric@anholt.net> Reviewed-by: Martin Sperl <kernel@martin.sperl.org> Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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@ -64,6 +64,7 @@ struct bcm2835_i2c_dev {
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int irq;
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struct i2c_adapter adapter;
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struct completion completion;
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struct i2c_msg *curr_msg;
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u32 msg_err;
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u8 *msg_buf;
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size_t msg_buf_remaining;
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@ -126,14 +127,13 @@ static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
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return IRQ_HANDLED;
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}
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if (val & BCM2835_I2C_S_RXD) {
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bcm2835_drain_rxfifo(i2c_dev);
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if (!(val & BCM2835_I2C_S_DONE))
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return IRQ_HANDLED;
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}
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if (val & BCM2835_I2C_S_DONE) {
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if (i2c_dev->msg_buf_remaining)
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if (i2c_dev->curr_msg->flags & I2C_M_RD) {
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bcm2835_drain_rxfifo(i2c_dev);
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val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
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}
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if ((val & BCM2835_I2C_S_RXD) || i2c_dev->msg_buf_remaining)
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i2c_dev->msg_err = BCM2835_I2C_S_LEN;
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else
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i2c_dev->msg_err = 0;
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@ -141,11 +141,16 @@ static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
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return IRQ_HANDLED;
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}
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if (val & BCM2835_I2C_S_TXD) {
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if (val & BCM2835_I2C_S_TXW) {
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bcm2835_fill_txfifo(i2c_dev);
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return IRQ_HANDLED;
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}
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if (val & BCM2835_I2C_S_RXR) {
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bcm2835_drain_rxfifo(i2c_dev);
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return IRQ_HANDLED;
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}
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return IRQ_NONE;
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}
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@ -155,6 +160,7 @@ static int bcm2835_i2c_xfer_msg(struct bcm2835_i2c_dev *i2c_dev,
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u32 c;
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unsigned long time_left;
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i2c_dev->curr_msg = msg;
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i2c_dev->msg_buf = msg->buf;
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i2c_dev->msg_buf_remaining = msg->len;
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reinit_completion(&i2c_dev->completion);
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