[PATCH v2 09/11] i2c: npcm: Handle spurious interrupts

Tyrone Ting
2022-02-20T03:57:25Z

From: Tali Perry <tali.perry1@gmail.com>

In order to better handle spurious interrupts:
1. Disable incoming interrupts in master only mode.
2. Clear end of busy (EOB) after every interrupt.
3. Return correct status during interrupt.

Fixes: 56a1485b102e ("i2c: npcm7xx: Add Nuvoton NPCM I2C controller driver")
Signed-off-by: Tali Perry <tali.perry1@gmail.com>
Signed-off-by: Tyrone Ting <kfting@nuvoton.com>
---
drivers/i2c/busses/i2c-npcm7xx.c | 92 ++++++++++++++++++++++----------
1 file changed, 63 insertions(+), 29 deletions(-)

diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
index 4715afcf9ac4..a265f6fdbf5c 100644
--- a/drivers/i2c/busses/i2c-npcm7xx.c
+++ b/drivers/i2c/busses/i2c-npcm7xx.c
@@ -564,6 +564,15 @@ static inline void npcm_i2c_nack(struct npcm_i2c *bus)
iowrite8(val, bus->reg + NPCM_I2CCTL1);
}

+static inline void npcm_i2c_clear_master_status(struct npcm_i2c *bus)
+{
+ u8 val;
+
+ /* Clear NEGACK, STASTR and BER bits */
+ val = NPCM_I2CST_BER | NPCM_I2CST_NEGACK | NPCM_I2CST_STASTR;
+ iowrite8(val, bus->reg + NPCM_I2CST);
+}
+
#if IS_ENABLED(CONFIG_I2C_SLAVE)
static void npcm_i2c_slave_int_enable(struct npcm_i2c *bus, bool enable)
{
@@ -643,8 +652,8 @@ static void npcm_i2c_reset(struct npcm_i2c *bus)
iowrite8(NPCM_I2CCST_BB, bus->reg + NPCM_I2CCST);
iowrite8(0xFF, bus->reg + NPCM_I2CST);

- /* Clear EOB bit */
- iowrite8(NPCM_I2CCST3_EO_BUSY, bus->reg + NPCM_I2CCST3);
+ /* Clear and disable EOB */
+ npcm_i2c_eob_int(bus, false);

/* Clear all fifo bits: */
iowrite8(NPCM_I2CFIF_CTS_CLR_FIFO, bus->reg + NPCM_I2CFIF_CTS);
@@ -656,6 +665,9 @@ static void npcm_i2c_reset(struct npcm_i2c *bus)
}
#endif

+ /* clear status bits for spurious interrupts */
+ npcm_i2c_clear_master_status(bus);
+
bus->state = I2C_IDLE;
}

@@ -818,15 +830,6 @@ static void npcm_i2c_read_fifo(struct npcm_i2c *bus, u8 bytes_in_fifo)
}
}

-static inline void npcm_i2c_clear_master_status(struct npcm_i2c *bus)
-{
- u8 val;
-
- /* Clear NEGACK, STASTR and BER bits */
- val = NPCM_I2CST_BER | NPCM_I2CST_NEGACK | NPCM_I2CST_STASTR;
- iowrite8(val, bus->reg + NPCM_I2CST);
-}
-
static void npcm_i2c_master_abort(struct npcm_i2c *bus)
{
/* Only current master is allowed to issue a stop condition */
@@ -1234,7 +1237,16 @@ static irqreturn_t npcm_i2c_int_slave_handler(struct npcm_i2c *bus)
ret = IRQ_HANDLED;
} /* SDAST */

- return ret;
+ /*
+ * if irq is not one of the above, make sure EOB is disabled and all
+ * status bits are cleared.
+ */
+ if (ret == IRQ_NONE) {
+ npcm_i2c_eob_int(bus, false);
+ npcm_i2c_clear_master_status(bus);
+ }
+
+ return IRQ_HANDLED;
}

static int npcm_i2c_reg_slave(struct i2c_client *client)
@@ -1470,6 +1482,9 @@ static void npcm_i2c_irq_handle_nack(struct npcm_i2c *bus)
npcm_i2c_eob_int(bus, false);
npcm_i2c_master_stop(bus);

+ /* Clear SDA Status bit (by reading dummy byte) */
+ npcm_i2c_rd_byte(bus);
+
/*
* The bus is released from stall only after the SW clears
* NEGACK bit. Then a Stop condition is sent.
@@ -1477,6 +1492,8 @@ static void npcm_i2c_irq_handle_nack(struct npcm_i2c *bus)
npcm_i2c_clear_master_status(bus);
readx_poll_timeout_atomic(ioread8, bus->reg + NPCM_I2CCST, val,
!(val & NPCM_I2CCST_BUSY), 10, 200);
+ /* verify no status bits are still set after bus is released */
+ npcm_i2c_clear_master_status(bus);
}
bus->state = I2C_IDLE;

@@ -1675,10 +1692,10 @@ static int npcm_i2c_recovery_tgclk(struct i2c_adapter *_adap)
int iter = 27;

if ((npcm_i2c_get_SDA(_adap) == 1) && (npcm_i2c_get_SCL(_adap) == 1)) {
- dev_dbg(bus->dev, "bus%d recovery skipped, bus not stuck",
- bus->num);
+ dev_dbg(bus->dev, "bus%d-0x%x recovery skipped, bus not stuck",
+ bus->num, bus->dest_addr);
npcm_i2c_reset(bus);
- return status;
+ return 0;
}

npcm_i2c_int_enable(bus, false);
@@ -1912,6 +1929,7 @@ static int npcm_i2c_init_module(struct npcm_i2c *bus, enum i2c_mode mode,
bus_freq_hz < I2C_FREQ_MIN_HZ || bus_freq_hz > I2C_FREQ_MAX_HZ)
return -EINVAL;

+ npcm_i2c_int_enable(bus, false);
npcm_i2c_disable(bus);

/* Configure FIFO mode : */
@@ -1940,10 +1958,18 @@ static int npcm_i2c_init_module(struct npcm_i2c *bus, enum i2c_mode mode,
val = (val | NPCM_I2CCTL1_NMINTE) & ~NPCM_I2CCTL1_RWS;
iowrite8(val, bus->reg + NPCM_I2CCTL1);

- npcm_i2c_int_enable(bus, true);
-
npcm_i2c_reset(bus);

+ /* check HW is OK: SDA and SCL should be high at this point. */
+ if ((npcm_i2c_get_SDA(&bus->adap) == 0) ||
+ (npcm_i2c_get_SCL(&bus->adap) == 0)) {
+ dev_err(bus->dev, "I2C%d init fail: lines are low", bus->num);
+ dev_err(bus->dev, "SDA=%d SCL=%d", npcm_i2c_get_SDA(&bus->adap),
+ npcm_i2c_get_SCL(&bus->adap));
+ return -ENXIO;
+ }
+
+ npcm_i2c_int_enable(bus, true);
return 0;
}

@@ -1991,10 +2017,14 @@ static irqreturn_t npcm_i2c_bus_irq(int irq, void *dev_id)
#if IS_ENABLED(CONFIG_I2C_SLAVE)
if (bus->slave) {
bus->master_or_slave = I2C_SLAVE;
- return npcm_i2c_int_slave_handler(bus);
+ if (npcm_i2c_int_slave_handler(bus))
+ return IRQ_HANDLED;
}
#endif
- return IRQ_NONE;
+ /* clear status bits for spurious interrupts */
+ npcm_i2c_clear_master_status(bus);
+
+ return IRQ_HANDLED;
}

static bool npcm_i2c_master_start_xmit(struct npcm_i2c *bus,
@@ -2051,7 +2081,6 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
u8 *write_data, *read_data;
u8 slave_addr;
unsigned long timeout;
- int ret = 0;
bool read_block = false;
bool read_PEC = false;
u8 bus_busy;
@@ -2141,12 +2170,12 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
bus->read_block_use = read_block;

reinit_completion(&bus->cmd_complete);
- if (!npcm_i2c_master_start_xmit(bus, slave_addr, nwrite, nread,
- write_data, read_data, read_PEC,
- read_block))
- ret = -EBUSY;

- if (ret != -EBUSY) {
+ npcm_i2c_int_enable(bus, true);
+
+ if (npcm_i2c_master_start_xmit(bus, slave_addr, nwrite, nread,
+ write_data, read_data, read_PEC,
+ read_block)) {
time_left = wait_for_completion_timeout(&bus->cmd_complete,
timeout);

@@ -2160,26 +2189,31 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
}
}
}
- ret = bus->cmd_err;

/* if there was BER, check if need to recover the bus: */
if (bus->cmd_err == -EAGAIN)
- ret = i2c_recover_bus(adap);
+ bus->cmd_err = i2c_recover_bus(adap);

/*
* After any type of error, check if LAST bit is still set,
* due to a HW issue.
* It cannot be cleared without resetting the module.
*/
- if (bus->cmd_err &&
- (NPCM_I2CRXF_CTL_LAST_PEC & ioread8(bus->reg + NPCM_I2CRXF_CTL)))
+ else if (bus->cmd_err &&
+ (NPCM_I2CRXF_CTL_LAST_PEC & ioread8(bus->reg + NPCM_I2CRXF_CTL)))
npcm_i2c_reset(bus);

+ /* after any xfer, successful or not, stall and EOB must be disabled */
+ npcm_i2c_stall_after_start(bus, false);
+ npcm_i2c_eob_int(bus, false);
+
#if IS_ENABLED(CONFIG_I2C_SLAVE)
/* reenable slave if it was enabled */
if (bus->slave)
iowrite8((bus->slave->addr & 0x7F) | NPCM_I2CADDR_SAEN,
bus->reg + NPCM_I2CADDR1);
+#else
+ npcm_i2c_int_enable(bus, false);
#endif
return bus->cmd_err;
}
--
2.17.1