i3c: add mixed limited bus mode

The i3c bus spec defines a bus configuration where i2c devices don't
have a 50ns filter but support SCL running at SDR max rate (12.5MHz).

This patch introduces the limited bus mode so that users can use
a higher speed in presence of i2c devices index 1.

Signed-off-by: Vitor Soares <vitor.soares@synopsys.com>
Cc: Boris Brezillon <bbrezillon@kernel.org>
Cc: <linux-kernel@vger.kernel.org>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
index 54026be03998fc11524be2ac619aa83524fab3bf..1318adfe0216ec6d4d4ffb5f5fc22d267a82a70b 100644 (file)
--- a/drivers/i3c/master.c
+++ b/drivers/i3c/master.c
@@ -470,6 +470,7 @@ static int i3c_bus_init(struct i3c_bus *i3cbus)
 static const char * const i3c_bus_mode_strings[] = {
        [I3C_BUS_MODE_PURE] = "pure",
        [I3C_BUS_MODE_MIXED_FAST] = "mixed-fast",
+       [I3C_BUS_MODE_MIXED_LIMITED] = "mixed-limited",
        [I3C_BUS_MODE_MIXED_SLOW] = "mixed-slow",
 };
 
@@ -584,6 +585,7 @@ int i3c_bus_set_mode(struct i3c_bus *i3cbus, enum i3c_bus_mode mode,
                        i3cbus->scl_rate.i3c = I3C_BUS_TYP_I3C_SCL_RATE;
                break;
        case I3C_BUS_MODE_MIXED_FAST:
+       case I3C_BUS_MODE_MIXED_LIMITED:
                if (!i3cbus->scl_rate.i3c)
                        i3cbus->scl_rate.i3c = I3C_BUS_TYP_I3C_SCL_RATE;
                if (!i3cbus->scl_rate.i2c)
@@ -2487,6 +2489,9 @@ int i3c_master_register(struct i3c_master_controller *master,
                                mode = I3C_BUS_MODE_MIXED_FAST;
                        break;
                case I3C_LVR_I2C_INDEX(1):
+                       if (mode < I3C_BUS_MODE_MIXED_LIMITED)
+                               mode = I3C_BUS_MODE_MIXED_LIMITED;
+                       break;
                case I3C_LVR_I2C_INDEX(2):
                        if (mode < I3C_BUS_MODE_MIXED_SLOW)
                                mode = I3C_BUS_MODE_MIXED_SLOW;

diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h
index eca8337bdaa55388cbf4f05c55090c75d6623d2b..1f08fa8d69d2725e204f761260692b610b89b31e 100644 (file)
--- a/include/linux/i3c/master.h
+++ b/include/linux/i3c/master.h
@@ -250,12 +250,17 @@ struct i3c_device {
  *                          the bus. The only impact in this mode is that the
  *                          high SCL pulse has to stay below 50ns to trick I2C
  *                          devices when transmitting I3C frames
+ * @I3C_BUS_MODE_MIXED_LIMITED: I2C devices without 50ns spike filter are
+ *                             present on the bus. However they allow
+ *                             compliance up to the maximum SDR SCL clock
+ *                             frequency.
  * @I3C_BUS_MODE_MIXED_SLOW: I2C devices without 50ns spike filter are present
  *                          on the bus
  */
 enum i3c_bus_mode {
        I3C_BUS_MODE_PURE,
        I3C_BUS_MODE_MIXED_FAST,
+       I3C_BUS_MODE_MIXED_LIMITED,
        I3C_BUS_MODE_MIXED_SLOW,
 };