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i2c: imx: Synthesize end of transaction events without idle interrupts
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Only the Layerscape SoCs have interrupts on bus idle, which facilitate
sending events which complete slave bus transactions.

Add support for synthesizing missing events. If we see a master request,
or a newly addressed slave request, if the last event sent to the backend
was I2C_SLAVE_READ_REQUESTED, send the backend a I2C_SLAVE_READ_PROCESSED
followed by I2C_SLAVE_STOP. For all other events, send an I2C_SLAVE_STOP.

Signed-off-by: Kevin Paul Herbert <kph@platinasystems.com>
Tested-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
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@kph @wsakernel
kph authored and wsakernel committed Feb 1, 2021
1 parent e037129 commit 05ae60b
Showing 1 changed file with 52 additions and 7 deletions.
59 changes: 52 additions & 7 deletions drivers/i2c/busses/i2c-imx.c
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Original file line number Diff line number Diff line change
Expand Up @@ -209,6 +209,7 @@ struct imx_i2c_struct {

struct imx_i2c_dma *dma;
struct i2c_client *slave;
enum i2c_slave_event last_slave_event;
};

static const struct imx_i2c_hwdata imx1_i2c_hwdata = {
Expand Down Expand Up @@ -675,6 +676,36 @@ static void i2c_imx_enable_bus_idle(struct imx_i2c_struct *i2c_imx)
}
}

static void i2c_imx_slave_event(struct imx_i2c_struct *i2c_imx,
enum i2c_slave_event event, u8 *val)
{
i2c_slave_event(i2c_imx->slave, event, val);
i2c_imx->last_slave_event = event;
}

static void i2c_imx_slave_finish_op(struct imx_i2c_struct *i2c_imx)
{
u8 val;

while (i2c_imx->last_slave_event != I2C_SLAVE_STOP) {
switch (i2c_imx->last_slave_event) {
case I2C_SLAVE_READ_REQUESTED:
i2c_imx_slave_event(i2c_imx, I2C_SLAVE_READ_PROCESSED,
&val);
break;

case I2C_SLAVE_WRITE_REQUESTED:
case I2C_SLAVE_READ_PROCESSED:
case I2C_SLAVE_WRITE_RECEIVED:
i2c_imx_slave_event(i2c_imx, I2C_SLAVE_STOP, &val);
break;

case I2C_SLAVE_STOP:
break;
}
}
}

static irqreturn_t i2c_imx_slave_isr(struct imx_i2c_struct *i2c_imx,
unsigned int status, unsigned int ctl)
{
Expand All @@ -687,9 +718,11 @@ static irqreturn_t i2c_imx_slave_isr(struct imx_i2c_struct *i2c_imx,
}

if (status & I2SR_IAAS) { /* Addressed as a slave */
i2c_imx_slave_finish_op(i2c_imx);
if (status & I2SR_SRW) { /* Master wants to read from us*/
dev_dbg(&i2c_imx->adapter.dev, "read requested");
i2c_slave_event(i2c_imx->slave, I2C_SLAVE_READ_REQUESTED, &value);
i2c_imx_slave_event(i2c_imx,
I2C_SLAVE_READ_REQUESTED, &value);

/* Slave transmit */
ctl |= I2CR_MTX;
Expand All @@ -699,7 +732,8 @@ static irqreturn_t i2c_imx_slave_isr(struct imx_i2c_struct *i2c_imx,
imx_i2c_write_reg(value, i2c_imx, IMX_I2C_I2DR);
} else { /* Master wants to write to us */
dev_dbg(&i2c_imx->adapter.dev, "write requested");
i2c_slave_event(i2c_imx->slave, I2C_SLAVE_WRITE_REQUESTED, &value);
i2c_imx_slave_event(i2c_imx,
I2C_SLAVE_WRITE_REQUESTED, &value);

/* Slave receive */
ctl &= ~I2CR_MTX;
Expand All @@ -710,17 +744,20 @@ static irqreturn_t i2c_imx_slave_isr(struct imx_i2c_struct *i2c_imx,
} else if (!(ctl & I2CR_MTX)) { /* Receive mode */
if (status & I2SR_IBB) { /* No STOP signal detected */
value = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
i2c_slave_event(i2c_imx->slave, I2C_SLAVE_WRITE_RECEIVED, &value);
i2c_imx_slave_event(i2c_imx,
I2C_SLAVE_WRITE_RECEIVED, &value);
} else { /* STOP signal is detected */
dev_dbg(&i2c_imx->adapter.dev,
"STOP signal detected");
i2c_slave_event(i2c_imx->slave, I2C_SLAVE_STOP, &value);
i2c_imx_slave_event(i2c_imx,
I2C_SLAVE_STOP, &value);
}
} else if (!(status & I2SR_RXAK)) { /* Transmit mode received ACK */
ctl |= I2CR_MTX;
imx_i2c_write_reg(ctl, i2c_imx, IMX_I2C_I2CR);

i2c_slave_event(i2c_imx->slave, I2C_SLAVE_READ_PROCESSED, &value);
i2c_imx_slave_event(i2c_imx,
I2C_SLAVE_READ_PROCESSED, &value);

imx_i2c_write_reg(value, i2c_imx, IMX_I2C_I2DR);
} else { /* Transmit mode received NAK */
Expand Down Expand Up @@ -761,6 +798,7 @@ static int i2c_imx_reg_slave(struct i2c_client *client)
return -EBUSY;

i2c_imx->slave = client;
i2c_imx->last_slave_event = I2C_SLAVE_STOP;

/* Resume */
ret = pm_runtime_get_sync(i2c_imx->adapter.dev.parent);
Expand Down Expand Up @@ -813,10 +851,17 @@ static irqreturn_t i2c_imx_isr(int irq, void *dev_id)

status = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
ctl = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);

if (status & I2SR_IIF) {
i2c_imx_clear_irq(i2c_imx, I2SR_IIF);
if (i2c_imx->slave && !(ctl & I2CR_MSTA))
return i2c_imx_slave_isr(i2c_imx, status, ctl);
if (i2c_imx->slave) {
if (!(ctl & I2CR_MSTA)) {
return i2c_imx_slave_isr(i2c_imx, status, ctl);
} else if (i2c_imx->last_slave_event !=
I2C_SLAVE_STOP) {
i2c_imx_slave_finish_op(i2c_imx);
}
}
return i2c_imx_master_isr(i2c_imx, status);
}

Expand Down

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