On 6/12/19 6:55 AM, Dmitry Osipenko wrote:
11.06.2019 13:51, Bitan Biswas пишет:
Fix expression for residual bytes(less than word) transfer
in I2C PIO mode RX/TX.
Signed-off-by: Bitan Biswas <bbiswas@xxxxxxxxxx>
---
drivers/i2c/busses/i2c-tegra.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 4dfb4c1..0596c12 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -514,7 +514,8 @@ static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev)
* If there is a partial word at the end of buf, handle it manually to
* prevent overwriting past the end of buf
*/
- if (rx_fifo_avail > 0 && buf_remaining > 0) {
+ if (rx_fifo_avail > 0 &&
+ (buf_remaining > 0 && buf_remaining < BYTES_PER_FIFO_WORD)) {
The buf_remaining >= BYTES_PER_FIFO_WORD is not possible to happen
because there are three possible cases:
1) buf_remaining > rx_fifo_avail * 4:
In this case rx_fifo_avail = 0
2) buf_remaining < rx_fifo_avail * 4;
In this case buf_remaining is always < 4 because
words_to_transfer is a buf_remaining rounded down to 4
and then divided by 4. Hence:
buf_remaining -= (buf_remaining / 4) * 4 always results
into buf_remaining < 4.
3) buf_remaining == rx_fifo_avail * 4:
In this case rx_fifo_avail = 0 and buf_remaining = 0.
Case 2 should never happen and means that something gone wrong.
Yes I now agree with you. The first condition "rx_fifo_avail > 0"
failure will take care and prevent need for additional checks.
BUG_ON(buf_remaining > 3);
val = i2c_readl(i2c_dev, I2C_RX_FIFO);
val = cpu_to_le32(val);
@@ -557,11 +558,10 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev)
words_to_transfer = tx_fifo_avail;
/*
- * Update state before writing to FIFO. If this casues us
+ * Update state before writing to FIFO. If this causes us
* to finish writing all bytes (AKA buf_remaining goes to 0) we
* have a potential for an interrupt (PACKET_XFER_COMPLETE is
- * not maskable). We need to make sure that the isr sees
- * buf_remaining as 0 and doesn't call us back re-entrantly.
+ * not maskable).
*/
buf_remaining -= words_to_transfer * BYTES_PER_FIFO_WORD;
tx_fifo_avail -= words_to_transfer;
@@ -580,7 +580,8 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev)
* prevent reading past the end of buf, which could cross a page
* boundary and fault.
*/
- if (tx_fifo_avail > 0 && buf_remaining > 0) {
+ if (tx_fifo_avail > 0 &&
+ (buf_remaining > 0 && buf_remaining < BYTES_PER_FIFO_WORD)) {
BUG_ON(buf_remaining > 3);
memcpy(&val, buf, buf_remaining);
val = le32_to_cpu(val);
Same as for RX.
Yes shall discard this patch from the next update.
-Thanks,
Bitan
