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i2c: rcar: fix NACK handling when being a target

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When this controller is a target, the NACK handling had two issues.
First, the return value from the backend was not checked on the initial
WRITE_REQUESTED. So, the driver missed to send a NACK in this case.
Also, the NACK always arrives one byte late on the bus, even in the
WRITE_RECEIVED case. This seems to be a HW issue. We should then not
rely on the backend to correctly NACK the superfluous byte as well. Fix
both issues by introducing a flag which gets set whenever the backend
requests a NACK and keep sending it until we get a STOP condition.

Fixes: de20d1857d ("i2c: rcar: add slave support")
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
This commit is contained in:
Wolfram Sang 2025-01-15 13:36:23 +01:00
parent 385f2dbbc9
commit 093f70c134
1 changed files with 15 additions and 5 deletions
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20
drivers/i2c/busses/i2c-rcar.c
View file

@ -130,6 +130,8 @@
#define ID_P_PM_BLOCKED BIT(31)
#define ID_P_MASK GENMASK(31, 27)
#define ID_SLAVE_NACK BIT(0)
enum rcar_i2c_type {
I2C_RCAR_GEN1,
I2C_RCAR_GEN2,
@ -166,6 +168,7 @@ struct rcar_i2c_priv {
int irq;
struct i2c_client *host_notify_client;
u8 slave_flags;
};
#define rcar_i2c_priv_to_dev(p) ((p)->adap.dev.parent)
@ -655,6 +658,7 @@ static bool rcar_i2c_slave_irq(struct rcar_i2c_priv *priv)
{
u32 ssr_raw, ssr_filtered;
u8 value;
int ret;
ssr_raw = rcar_i2c_read(priv, ICSSR) & 0xff;
ssr_filtered = ssr_raw & rcar_i2c_read(priv, ICSIER);
@ -670,7 +674,10 @@ static bool rcar_i2c_slave_irq(struct rcar_i2c_priv *priv)
rcar_i2c_write(priv, ICRXTX, value);
rcar_i2c_write(priv, ICSIER, SDE | SSR | SAR);
} else {
i2c_slave_event(priv->slave, I2C_SLAVE_WRITE_REQUESTED, &value);
ret = i2c_slave_event(priv->slave, I2C_SLAVE_WRITE_REQUESTED, &value);
if (ret)
priv->slave_flags |= ID_SLAVE_NACK;
rcar_i2c_read(priv, ICRXTX); /* dummy read */
rcar_i2c_write(priv, ICSIER, SDR | SSR | SAR);
}
@ -683,18 +690,21 @@ static bool rcar_i2c_slave_irq(struct rcar_i2c_priv *priv)
if (ssr_filtered & SSR) {
i2c_slave_event(priv->slave, I2C_SLAVE_STOP, &value);
rcar_i2c_write(priv, ICSCR, SIE | SDBS); /* clear our NACK */
priv->slave_flags &= ~ID_SLAVE_NACK;
rcar_i2c_write(priv, ICSIER, SAR);
rcar_i2c_write(priv, ICSSR, ~SSR & 0xff);
}
/* master wants to write to us */
if (ssr_filtered & SDR) {
int ret;
value = rcar_i2c_read(priv, ICRXTX);
ret = i2c_slave_event(priv->slave, I2C_SLAVE_WRITE_RECEIVED, &value);
/* Send NACK in case of error */
rcar_i2c_write(priv, ICSCR, SIE | SDBS | (ret < 0 ? FNA : 0));
if (ret)
priv->slave_flags |= ID_SLAVE_NACK;
/* Send NACK in case of error, but it will come 1 byte late :( */
rcar_i2c_write(priv, ICSCR, SIE | SDBS |
(priv->slave_flags & ID_SLAVE_NACK ? FNA : 0));
rcar_i2c_write(priv, ICSSR, ~SDR & 0xff);
}