media: ov5640: Re-work MIPI startup sequence

Rework the MIPI interface startup sequence with the following changes:

- Remove MIPI bus initialization from the initial settings blob
- At set_power(1) time power up MIPI Tx/Rx and set data and clock lanes in
  LP11 during 'sleep' and 'idle' with MIPI clock in non-continuous mode.
- At s_stream time enable/disable the MIPI interface output.
- Restore default settings at set_power(0) time.

Before this commit the sensor MIPI interface was initialized with settings
that require a start/stop sequence at power-up time in order to force lanes
into LP11 state, as they were initialized in LP00 when in 'sleep mode',
which is assumed to be the sensor manual definition for the D-PHY defined
stop mode.

The stream start/stop was performed by enabling disabling clock gating,
and had the side effect to change the lanes sleep mode configuration when
stream was stopped.

Clock gating/ungating:
-       ret = ov5640_mod_reg(sensor, OV5640_REG_MIPI_CTRL00, BIT(5),
-                            on ? 0 : BIT(5));
-       if (ret)

Set lanes in LP11 when in 'sleep mode':
-       ret = ov5640_write_reg(sensor, OV5640_REG_PAD_OUTPUT00,
-                              on ? 0x00 : 0x70);

This commit fixes an issue reported by Jagan Teki on i.MX6 platforms that
prevents the host interface from powering up correctly:
https://lkml.org/lkml/2018/6/1/38

It also improves MIPI capture operations stability on my testing platform
where MIPI capture often failed and returned all-purple frames.

Fixes: f22996db ("media: ov5640: add support of DVP parallel interface")

Tested-by: Steve Longerbeam <slongerbeam@gmail.com> (i.MX6q SabreSD, CSI-2)
Tested-by: Loic Poulain <loic.poulain@linaro.org> (Dragonboard-410c, CSI-2)
Reported-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/i2c/ov5640.c

@@ -287,10 +287,10 @@ static const struct reg_value ov5640_init_setting_30fps_VGA[] = {
 	{0x3a0d, 0x04, 0, 0}, {0x3a14, 0x03, 0, 0}, {0x3a15, 0xd8, 0, 0},
 	{0x4001, 0x02, 0, 0}, {0x4004, 0x02, 0, 0}, {0x3000, 0x00, 0, 0},
 	{0x3002, 0x1c, 0, 0}, {0x3004, 0xff, 0, 0}, {0x3006, 0xc3, 0, 0},
-	{0x300e, 0x45, 0, 0}, {0x302e, 0x08, 0, 0}, {0x4300, 0x3f, 0, 0},
+	{0x302e, 0x08, 0, 0}, {0x4300, 0x3f, 0, 0},
 	{0x501f, 0x00, 0, 0}, {0x4713, 0x03, 0, 0}, {0x4407, 0x04, 0, 0},
 	{0x440e, 0x00, 0, 0}, {0x460b, 0x35, 0, 0}, {0x460c, 0x22, 0, 0},
-	{0x4837, 0x0a, 0, 0}, {0x4800, 0x04, 0, 0}, {0x3824, 0x02, 0, 0},
+	{0x4837, 0x0a, 0, 0}, {0x3824, 0x02, 0, 0},
 	{0x5000, 0xa7, 0, 0}, {0x5001, 0xa3, 0, 0}, {0x5180, 0xff, 0, 0},
 	{0x5181, 0xf2, 0, 0}, {0x5182, 0x00, 0, 0}, {0x5183, 0x14, 0, 0},
 	{0x5184, 0x25, 0, 0}, {0x5185, 0x24, 0, 0}, {0x5186, 0x09, 0, 0},
@@ -1103,12 +1103,25 @@ static int ov5640_set_stream_mipi(struct ov5640_dev *sensor, bool on)
 {
 	int ret;
 
-	ret = ov5640_mod_reg(sensor, OV5640_REG_MIPI_CTRL00, BIT(5),
-			     on ? 0 : BIT(5));
-	if (ret)
-		return ret;
-	ret = ov5640_write_reg(sensor, OV5640_REG_PAD_OUTPUT00,
-			       on ? 0x00 : 0x70);
+	/*
+	 * Enable/disable the MIPI interface
+	 *
+	 * 0x300e = on ? 0x45 : 0x40
+	 *
+	 * FIXME: the sensor manual (version 2.03) reports
+	 * [7:5] = 000  : 1 data lane mode
+	 * [7:5] = 001  : 2 data lanes mode
+	 * But this settings do not work, while the following ones
+	 * have been validated for 2 data lanes mode.
+	 *
+	 * [7:5] = 010	: 2 data lanes mode
+	 * [4] = 0	: Power up MIPI HS Tx
+	 * [3] = 0	: Power up MIPI LS Rx
+	 * [2] = 1/0	: MIPI interface enable/disable
+	 * [1:0] = 01/00: FIXME: 'debug'
+	 */
+	ret = ov5640_write_reg(sensor, OV5640_REG_IO_MIPI_CTRL00,
+			       on ? 0x45 : 0x40);
 	if (ret)
 		return ret;
 
@@ -1787,23 +1800,69 @@ static int ov5640_set_power(struct ov5640_dev *sensor, bool on)
 		if (ret)
 			goto power_off;
 
+		/* We're done here for DVP bus, while CSI-2 needs setup. */
+		if (sensor->ep.bus_type != V4L2_MBUS_CSI2)
+			return 0;
+
+		/*
+		 * Power up MIPI HS Tx and LS Rx; 2 data lanes mode
+		 *
+		 * 0x300e = 0x40
+		 * [7:5] = 010	: 2 data lanes mode (see FIXME note in
+		 *		  "ov5640_set_stream_mipi()")
+		 * [4] = 0	: Power up MIPI HS Tx
+		 * [3] = 0	: Power up MIPI LS Rx
+		 * [2] = 0	: MIPI interface disabled
+		 */
+		ret = ov5640_write_reg(sensor,
+				       OV5640_REG_IO_MIPI_CTRL00, 0x40);
+		if (ret)
+			goto power_off;
+
+		/*
+		 * Gate clock and set LP11 in 'no packets mode' (idle)
+		 *
+		 * 0x4800 = 0x24
+		 * [5] = 1	: Gate clock when 'no packets'
+		 * [2] = 1	: MIPI bus in LP11 when 'no packets'
+		 */
+		ret = ov5640_write_reg(sensor,
+				       OV5640_REG_MIPI_CTRL00, 0x24);
+		if (ret)
+			goto power_off;
+
+		/*
+		 * Set data lanes and clock in LP11 when 'sleeping'
+		 *
+		 * 0x3019 = 0x70
+		 * [6] = 1	: MIPI data lane 2 in LP11 when 'sleeping'
+		 * [5] = 1	: MIPI data lane 1 in LP11 when 'sleeping'
+		 * [4] = 1	: MIPI clock lane in LP11 when 'sleeping'
+		 */
+		ret = ov5640_write_reg(sensor,
+				       OV5640_REG_PAD_OUTPUT00, 0x70);
+		if (ret)
+			goto power_off;
+
+		/* Give lanes some time to coax into LP11 state. */
+		usleep_range(500, 1000);
+
+	} else {
 		if (sensor->ep.bus_type == V4L2_MBUS_CSI2) {
-			/*
-			 * start streaming briefly followed by stream off in
-			 * order to coax the clock lane into LP-11 state.
-			 */
-			ret = ov5640_set_stream_mipi(sensor, true);
-			if (ret)
-				goto power_off;
-			usleep_range(1000, 2000);
-			ret = ov5640_set_stream_mipi(sensor, false);
-			if (ret)
-				goto power_off;
+			/* Reset MIPI bus settings to their default values. */
+			ov5640_write_reg(sensor,
+					 OV5640_REG_IO_MIPI_CTRL00, 0x58);
+			ov5640_write_reg(sensor,
+					 OV5640_REG_MIPI_CTRL00, 0x04);
+			ov5640_write_reg(sensor,
+					 OV5640_REG_PAD_OUTPUT00, 0x00);
 		}
 
-		return 0;
+		ov5640_set_power_off(sensor);
 	}
 
+	return 0;
+
 power_off:
 	ov5640_set_power_off(sensor);
 	return ret;