This is a note to let you know that I've just added the patch titled
i2c: rcar: fix NACK handling when being a target
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
i2c-rcar-fix-nack-handling-when-being-a-target.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 1a79333fcf36e75c964376fec336a882280f3488
Author: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
Date: Wed Jan 15 13:36:23 2025 +0100
i2c: rcar: fix NACK handling when being a target
[ Upstream commit 093f70c134f70e4632b295240f07d2b50b74e247 ]
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: de20d1857dd6 ("i2c: rcar: add slave support")
Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index 7a6bae9df568b..08b1580d59c98 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -112,6 +112,8 @@
#define ID_P_PM_BLOCKED BIT(31)
#define ID_P_MASK GENMASK(31, 28)
+#define ID_SLAVE_NACK BIT(0)
+
enum rcar_i2c_type {
I2C_RCAR_GEN1,
I2C_RCAR_GEN2,
@@ -145,6 +147,7 @@ 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)
@@ -573,6 +576,7 @@ 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);
@@ -588,7 +592,10 @@ 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);
}
@@ -601,18 +608,21 @@ 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);
}
