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From:   Vitor Soares <Vitor.Soares@synopsys.com>
To:     linux-i3c@lists.infradead.org
Cc:     Joao.Pinto@synopsys.com, Vitor Soares <Vitor.Soares@synopsys.com>,
        Boris Brezillon <bbrezillon@kernel.org>,
        linux-kernel@vger.kernel.org
Subject: [PATCH v3 2/3] i3c: add mixed limited bus mode
Date:   Tue, 11 Jun 2019 16:06:44 +0200
Message-Id: <cdfdf31d1e52b7569f686c50e6f56163d21d8b36.1560261604.git.vitor.soares@synopsys.com>
In-Reply-To: <cover.1560261604.git.vitor.soares@synopsys.com>
References: <cover.1560261604.git.vitor.soares@synopsys.com>
In-Reply-To: <cover.1560261604.git.vitor.soares@synopsys.com>
References: <cover.1560261604.git.vitor.soares@synopsys.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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>
---
Changes in v3:
  None

Changes in v2:
  Enhance commit message

 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 f8e580e..025925c 100644
--- 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",
 };
 
@@ -585,6 +586,7 @@ 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)
@@ -2490,6 +2492,9 @@ 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 f13fd8b..89ea461 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