[PATCH v2 5/6] i2c: xiic: Only ever transfer single message

Marek Vasut
2021-08-23T21:42:21Z

Transferring multiple messages via XIIC suffers from strange interaction
between the interrupt status/enable register flags. These flags are being
reused in the hardware to indicate different things for read and write
transfer, and doing multiple transactions becomes horribly complex. Just
send a single transaction and reload the controller with another message
once the transaction is done in the interrupt handler thread.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Cc: Wolfram Sang <wsa@kernel.org>
---
V2: No change
---
drivers/i2c/busses/i2c-xiic.c | 44 ++++++++---------------------------
1 file changed, 10 insertions(+), 34 deletions(-)

diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
index f7277629923ff..6cd7830fe4898 100644
--- a/drivers/i2c/busses/i2c-xiic.c
+++ b/drivers/i2c/busses/i2c-xiic.c
@@ -609,8 +609,6 @@ static void xiic_start_send(struct xiic_i2c *i2c)
{
struct i2c_msg *msg = i2c->tx_msg;

- xiic_irq_clr(i2c, XIIC_INTR_TX_ERROR_MASK);
-
dev_dbg(i2c->adap.dev.parent, "%s entry, msg: %p, len: %d",
__func__, msg, msg->len);
dev_dbg(i2c->adap.dev.parent, "%s entry, ISR: 0x%x, CR: 0x%x\n",
@@ -628,16 +626,17 @@ static void xiic_start_send(struct xiic_i2c *i2c)
xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET, data);
}

- xiic_fill_tx_fifo(i2c);
-
/* Clear any pending Tx empty, Tx Error and then enable them. */
xiic_irq_clr_en(i2c, XIIC_INTR_TX_EMPTY_MASK | XIIC_INTR_TX_ERROR_MASK |
- XIIC_INTR_BNB_MASK);
+ XIIC_INTR_BNB_MASK |
+ ((i2c->nmsgs > 1 || xiic_tx_space(i2c)) ?
+ XIIC_INTR_TX_HALF_MASK : 0));
+
+ xiic_fill_tx_fifo(i2c);
}

static void __xiic_start_xfer(struct xiic_i2c *i2c)
{
- int first = 1;
int fifo_space = xiic_tx_fifo_space(i2c);
dev_dbg(i2c->adap.dev.parent, "%s entry, msg: %p, fifos space: %d\n",
__func__, i2c->tx_msg, fifo_space);
@@ -648,35 +647,12 @@ static void __xiic_start_xfer(struct xiic_i2c *i2c)
i2c->rx_pos = 0;
i2c->tx_pos = 0;
i2c->state = STATE_START;
- while ((fifo_space >= 2) && (first || (i2c->nmsgs > 1))) {
- if (!first) {
- i2c->nmsgs--;
- i2c->tx_msg++;
- i2c->tx_pos = 0;
- } else
- first = 0;
-
- if (i2c->tx_msg->flags & I2C_M_RD) {
- /* we dont date putting several reads in the FIFO */
- xiic_start_recv(i2c);
- return;
- } else {
- xiic_start_send(i2c);
- if (xiic_tx_space(i2c) != 0) {
- /* the message could not be completely sent */
- break;
- }
- }
-
- fifo_space = xiic_tx_fifo_space(i2c);
+ if (i2c->tx_msg->flags & I2C_M_RD) {
+ /* we dont date putting several reads in the FIFO */
+ xiic_start_recv(i2c);
+ } else {
+ xiic_start_send(i2c);
}
-
- /* there are more messages or the current one could not be completely
- * put into the FIFO, also enable the half empty interrupt
- */
- if (i2c->nmsgs > 1 || xiic_tx_space(i2c))
- xiic_irq_clr_en(i2c, XIIC_INTR_TX_HALF_MASK);
-
}

static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num)
--
2.32.0