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91 lines
2.9 KiB
Diff
91 lines
2.9 KiB
Diff
From 89b466914a0d49f08d00be25556ba22497b9a284 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Noralf=20Tr=C3=B8nnes?= <noralf@tronnes.org>
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Date: Sat, 17 Sep 2016 15:07:10 +0200
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Subject: [PATCH] i2c: bcm2835: Fix hang for writing messages larger than 16
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bytes
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Writing messages larger than the FIFO size results in a hang, rendering
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the machine unusable. This is because the RXD status flag is set on the
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first interrupt which results in bcm2835_drain_rxfifo() stealing bytes
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from the buffer. The controller continues to trigger interrupts waiting
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for the missing bytes, but bcm2835_fill_txfifo() has none to give.
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In this situation wait_for_completion_timeout() apparently is unable to
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stop the madness.
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The BCM2835 ARM Peripherals datasheet has this to say about the flags:
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TXD: is set when the FIFO has space for at least one byte of data.
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RXD: is set when the FIFO contains at least one byte of data.
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TXW: is set during a write transfer and the FIFO is less than full.
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RXR: is set during a read transfer and the FIFO is or more full.
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Implementing the logic from the downstream i2c-bcm2708 driver solved
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the hang problem.
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Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
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Reviewed-by: Eric Anholt <eric@anholt.net>
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Reviewed-by: Martin Sperl <kernel@martin.sperl.org>
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---
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drivers/i2c/busses/i2c-bcm2835.c | 22 ++++++++++++++--------
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1 file changed, 14 insertions(+), 8 deletions(-)
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--- a/drivers/i2c/busses/i2c-bcm2835.c
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+++ b/drivers/i2c/busses/i2c-bcm2835.c
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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 t
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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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-
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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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+
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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 t
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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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+
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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 b
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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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