linux-kernel - [PATCH 2/3] i3c: add mixed limited bus mode

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Message-Id: <a3bf32dadd9b0135442526cc77fec5726e6e617d.1555350118.git.vitor.soares@synopsys.com>
Date:   Mon, 15 Apr 2019 20:42:46 +0200
From:   Vitor Soares <vitor.soares@...opsys.com>
To:     vitor.soares@...opsys.com
Cc:     Vitor Soares <vitor.soares@...opsys.com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] i3c: add mixed limited bus mode

The i3c bus spec define a bus configuration where the i2c devices
doesn't have the 50ns filter yet they allow the SDR max speed.

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

Signed-off-by: Vitor Soares <vitor.soares@...opsys.com>
Cc: Boris Brezillon <bbrezillon@...nel.org>
Cc: <linux-kernel@...r.kernel.org>
---
 drivers/i3c/master.c       | 5 +++++
 include/linux/i3c/master.h | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
index 1c4a86a..46d3774 100644
--- a/drivers/i3c/master.c
+++ b/drivers/i3c/master.c
@@ -463,6 +463,7 @@ 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",
 };
 
@@ -575,6 +576,7 @@ 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)
@@ -2481,6 +2483,9 @@ 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 44fb3cf..740235e 100644
--- 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 allows
+ *				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,
 };
 
-- 
2.7.4