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

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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>
This commit is contained in:
Noralf Trønnes 2016-10-03 22:06:08 +02:00 committed by Wolfram Sang
parent bc33b0ca11
commit e247454103
1 changed files with 14 additions and 8 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

18
drivers/i2c/busses/i2c-bcm2835.c
View file

@ -64,6 +64,7 @@ struct bcm2835_i2c_dev {
int irq;
struct i2c_adapter adapter;
struct completion completion;
struct i2c_msg *curr_msg;
u32 msg_err;
u8 *msg_buf;
size_t msg_buf_remaining;
@ -126,14 +127,13 @@ static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
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);
if (!(val & BCM2835_I2C_S_DONE))
return IRQ_HANDLED;
val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
}
if (val & BCM2835_I2C_S_DONE) {
if (i2c_dev->msg_buf_remaining)
if ((val & BCM2835_I2C_S_RXD) || i2c_dev->msg_buf_remaining)
i2c_dev->msg_err = BCM2835_I2C_S_LEN;
else
i2c_dev->msg_err = 0;
@ -141,11 +141,16 @@ static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
return IRQ_HANDLED;
}
if (val & BCM2835_I2C_S_TXD) {
if (val & BCM2835_I2C_S_TXW) {
bcm2835_fill_txfifo(i2c_dev);
return IRQ_HANDLED;
}
if (val & BCM2835_I2C_S_RXR) {
bcm2835_drain_rxfifo(i2c_dev);
return IRQ_HANDLED;
}
return IRQ_NONE;
}
@ -155,6 +160,7 @@ static int bcm2835_i2c_xfer_msg(struct bcm2835_i2c_dev *i2c_dev,
u32 c;
unsigned long time_left;
i2c_dev->curr_msg = msg;
i2c_dev->msg_buf = msg->buf;
i2c_dev->msg_buf_remaining = msg->len;
reinit_completion(&i2c_dev->completion);