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authorNoralf Trønnes <noralf@tronnes.org>2016-10-03 23:06:08 +0300
committerWolfram Sang <wsa@the-dreams.de>2016-11-07 03:48:31 +0300
commite2474541032db65d02bf88b6a8c2f954654b443f (patch)
tree0c7239f4055505840b535d2141c32c4c398fe585 /drivers/i2c/busses/i2c-bcm2835.c
parentbc33b0ca11e3df467777a4fa7639ba488c9d4911 (diff)
downloadlinux-e2474541032db65d02bf88b6a8c2f954654b443f.tar.xz
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>
Diffstat (limited to 'drivers/i2c/busses/i2c-bcm2835.c')
-rw-r--r--drivers/i2c/busses/i2c-bcm2835.c22
1 files changed, 14 insertions, 8 deletions
diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
index d4f3239b5686..f283b714aa79 100644
--- a/drivers/i2c/busses/i2c-bcm2835.c
+++ b/drivers/i2c/busses/i2c-bcm2835.c
@@ -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) {
- bcm2835_drain_rxfifo(i2c_dev);
- if (!(val & BCM2835_I2C_S_DONE))
- return IRQ_HANDLED;
- }
-
if (val & BCM2835_I2C_S_DONE) {
- if (i2c_dev->msg_buf_remaining)
+ if (i2c_dev->curr_msg->flags & I2C_M_RD) {
+ bcm2835_drain_rxfifo(i2c_dev);
+ val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
+ }
+
+ 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);