Re: [PATCH V6] i2c: tegra: remove BUG, BUG_ON
From: Bitan Biswas
Date: Mon Jun 17 2019 - 15:13:13 EST
On 6/14/19 10:51 AM, Dmitry Osipenko wrote:
14.06.2019 18:50, Bitan Biswas ÐÐÑÐÑ:
Remove redundant BUG_ON calls or replace with WARN_ON_ONCE
as needed. Remove BUG() and mask Rx interrupt similar as Tx
for message fully sent case. Add WARN_ON_ONCE check
for non-zero rx_fifo_avail in tegra_i2c_empty_rx_fifo()
after all processing. Error handling in tegra_i2c_empty_rx_fifo
caller is also added.
Signed-off-by: Bitan Biswas <bbiswas@xxxxxxxxxx>
---
drivers/i2c/busses/i2c-tegra.c | 46 ++++++++++++++++++++++++++++++++++--------
1 file changed, 38 insertions(+), 8 deletions(-)
diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 4dfb4c1..26a7c8c 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -73,6 +73,7 @@
#define I2C_ERR_NO_ACK BIT(0)
#define I2C_ERR_ARBITRATION_LOST BIT(1)
#define I2C_ERR_UNKNOWN_INTERRUPT BIT(2)
+#define I2C_ERR_UNEXPECTED_STATUS BIT(3)
What about I2C_ERR_RX_BUFFER_OVERFLOW?
OK.
#define PACKET_HEADER0_HEADER_SIZE_SHIFT 28
#define PACKET_HEADER0_PACKET_ID_SHIFT 16
@@ -515,15 +516,23 @@ static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev)
* prevent overwriting past the end of buf
*/
if (rx_fifo_avail > 0 && buf_remaining > 0) {
- BUG_ON(buf_remaining > 3);
+ /* buf_remaining > 3 check not needed as rx_fifo_avail == 0
+ * when (words_to_transfer was > rx_fifo_avail) earlier
+ * in this function
+ */
Please start all multiline comments with an empty "/*", it should be the correct
style. There are some places in the kernel where style like yours is used, but I
assume they are not very correct. Besides, yours variant is not consistent with the
style of the rest of comments in this source file. And put a dot in the end for
completeness. Same for the other comments in this patch.
OK
val = i2c_readl(i2c_dev, I2C_RX_FIFO);
val = cpu_to_le32(val);
memcpy(buf, &val, buf_remaining);
buf_remaining = 0;
rx_fifo_avail--;
}
Please add a newline here. All logical parts of the code should be separated to ease
reading and following.
OK
+ if (WARN_ON_ONCE(rx_fifo_avail))
+ return -EINVAL;
- BUG_ON(rx_fifo_avail > 0 && buf_remaining > 0);
+ /* buf_remaining > 0 at this point can only have rx_fifo_avail == 0
+ * as this corresponds to (words_to_transfer was > rx_fifo_avail)
+ * case earlier in this function
+ */
i2c_dev->msg_buf_remaining = buf_remaining;
i2c_dev->msg_buf = buf;
@@ -581,7 +590,10 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev)
* boundary and fault.
*/
if (tx_fifo_avail > 0 && buf_remaining > 0) {
- BUG_ON(buf_remaining > 3);
+ /* buf_remaining > 3 check not needed as tx_fifo_avail == 0
+ * when (words_to_transfer was > tx_fifo_avail) earlier
+ * in this function for non-zero words_to_transfer
+ */
memcpy(&val, buf, buf_remaining);
val = le32_to_cpu(val);
@@ -811,6 +823,7 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
u32 status;
const u32 status_err = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST;
struct tegra_i2c_dev *i2c_dev = dev_id;
+ int err_val;
status = i2c_readl(i2c_dev, I2C_INT_STATUS);
@@ -847,10 +860,21 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
if (!i2c_dev->is_curr_dma_xfer) {
if (i2c_dev->msg_read && (status & I2C_INT_RX_FIFO_DATA_REQ)) {
- if (i2c_dev->msg_buf_remaining)
- tegra_i2c_empty_rx_fifo(i2c_dev);
- else
- BUG();
+ err_val = tegra_i2c_empty_rx_fifo(i2c_dev);
+ if ((!(i2c_dev->msg_buf_remaining)) &&
Let's move this check into tegra_i2c_empty_rx_fifo() and return -EINVAL for that case.
This will make code to look cleaner.
OK.
+ (!(status & I2C_INT_PACKET_XFER_COMPLETE)) &&
It shouldn't matter that XFER_COMPLETE is set if RX FIFO isn't fully emptied because
it always shall be emptied. Hence this check is not needed and we should error out
regardless.
OK
+ err_val) {
+ /*
+ * Overflow error condition: message fully sent,
+ * with no XFER_COMPLETE interrupt but hardware
+ * asks to transfer more.
+ */
+ tegra_i2c_mask_irq(i2c_dev,
+ I2C_INT_RX_FIFO_DATA_REQ);
No need to mask RX_FIFO_DATA_REQ here because all interrupts are masked on "goto
err:", hence just remove the tegra_i2c_mask_irq().
+ i2c_dev->msg_err |=
+ I2C_ERR_UNEXPECTED_STATUS;
No need to split this into two lines because it's less than 80 chars, write this in a
single line.
OK
+ goto err;
+ }
}
if (!i2c_dev->msg_read && (status & I2C_INT_TX_FIFO_DATA_REQ)) {
@@ -876,7 +900,13 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
if (status & I2C_INT_PACKET_XFER_COMPLETE) {
if (i2c_dev->is_curr_dma_xfer)
i2c_dev->msg_buf_remaining = 0;
- BUG_ON(i2c_dev->msg_buf_remaining);
+ /* Underflow error condition: XFER_COMPLETE before message
+ * fully sent.
+ */
+ if (WARN_ON_ONCE(i2c_dev->msg_buf_remaining)) {
+ i2c_dev->msg_err |= I2C_ERR_UNKNOWN_INTERRUPT;
+ goto err;
+ }
complete(&i2c_dev->msg_complete);
}
goto done;
Please address comments in the next revision.
Sorry for the delayed reply. I shared Patch V7 with above changes
earlier today.
-regards,
Bitan