[PATCH 6/7] i2c: nomadik: add quirks max_len=2047 and no_zero_len_read

[Dmitry Guzman]

In Nomadik I2c controller, register I2C_MCR has 11-bit wide LENGTH
field. Its maximum value is 2047, so this is the maximum length of a
single message. It is less than the common maximum I2C message length in
I2C subsystem (8192), so define a quirk in order to report the
unsupported message without any attempt to transfer it.

Zero length reading doesn't work properly on this controller, so add
`I2C_AQ_NO_ZERO_LEN_READ` quirk flag.

Signed-off-by: Dmitry Guzman <Dmitry.Guzman@xxxxxxxxxxxx>
---
 drivers/i2c/busses/i2c-nomadik.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/i2c/busses/i2c-nomadik.c b/drivers/i2c/busses/i2c-nomadik.c
index 7d93fb3876dc1324003dd19884e3fd5cbba9cfbb..9cff0c2757fafeaf809395e02a5e754570f65e08 100644
--- a/drivers/i2c/busses/i2c-nomadik.c
+++ b/drivers/i2c/busses/i2c-nomadik.c
@@ -79,6 +79,9 @@
 #define I2C_MCR_STOP		BIT(14)		/* Stop condition */
 #define I2C_MCR_LENGTH		GENMASK(25, 15)	/* Transaction length */
 
+/* Controller hardware limitation of the message length */
+#define I2C_MAX_MSG_LENGTH	(I2C_MCR_LENGTH >> 15)
+
 /* Status register (SR) */
 #define I2C_SR_OP		GENMASK(1, 0)	/* Operation */
 #define I2C_SR_STATUS		GENMASK(3, 2)	/* controller status */
@@ -238,6 +241,12 @@ static int fault_codes[] = {
 	EIO
 };
 
+static const struct i2c_adapter_quirks nmk_i2c_quirks = {
+	.flags = I2C_AQ_NO_ZERO_LEN_READ,
+	.max_read_len  = I2C_MAX_MSG_LENGTH,
+	.max_write_len = I2C_MAX_MSG_LENGTH,
+};
+
 static inline void i2c_set_bit(void __iomem *reg, u32 mask)
 {
 	writel(readl(reg) | mask, reg);
@@ -1162,6 +1171,7 @@ static int nmk_i2c_probe(struct amba_device *adev, const struct amba_id *id)
 	adap->class = I2C_CLASS_DEPRECATED;
 	adap->algo = &nmk_i2c_algo;
 	adap->timeout = usecs_to_jiffies(priv->timeout_usecs);
+	adap->quirks = &nmk_i2c_quirks;
 	snprintf(adap->name, sizeof(adap->name),
 		 "Nomadik I2C at %pR", &adev->res);
 

-- 
2.43.0