> -----Original Message-----
> From: linux-i2c-owner@xxxxxxxxxxxxxxx <linux-i2c-owner@xxxxxxxxxxxxxxx> On
> Behalf Of Marek Vasut
> Sent: Saturday, June 13, 2020 8:38 PM
> To: linux-i2c@xxxxxxxxxxxxxxx
> Cc: Marek Vasut <marex@xxxxxxx>; Michal Simek <michals@xxxxxxxxxx>;
> Shubhrajyoti Datta <shubhraj@xxxxxxxxxx>; Wolfram Sang <wsa@xxxxxxxxxx>
> Subject: [PATCH 5/5] i2c: xiic: Only ever transfer single message
>
> 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@xxxxxxx>
> Cc: Michal Simek <michal.simek@xxxxxxxxxx>
> Cc: Shubhrajyoti Datta <shubhrajyoti.datta@xxxxxxxxxx>
> Cc: Wolfram Sang <wsa@xxxxxxxxxx>
> ---
> drivers/i2c/busses/i2c-xiic.c | 43 ++++++++---------------------------
> 1 file changed, 10 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c index
> e4c3427b2f3f5..fad0b84a273d1 100644
> --- a/drivers/i2c/busses/i2c-xiic.c
> +++ b/drivers/i2c/busses/i2c-xiic.c
> @@ -595,8 +595,6 @@ 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", @@
> -614,11 +612,13 @@ 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) @@ -634,35 +634,12 @@
> static void __xiic_start_xfer(struct xiic_i2c *i2c)
Can remove the definition of unused variable ("first").
> 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)
This patch is much needed to simplify the logic. Tested, working fine.
Raviteja N
