Re: [RFC PATCH 1/4] mipi-dsi-bus: add MIPI DSI bus support

On 10/07/2013 12:47 PM, Bert Kenward wrote:

On Tuesday September 24 2013 at 15:23, Andrzej Hajda wrote:

quoted

MIPI DSI is a high-speed serial interface to transmit
data from/to host to display module.

Signed-off-by: Andrzej Hajda <redacted>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
---
 drivers/video/display/Kconfig        |   4 +
 drivers/video/display/Makefile       |   1 +
 drivers/video/display/mipi-dsi-bus.c | 332
+++++++++++++++++++++++++++++++++++
 include/video/display.h              |   3 +
 include/video/mipi-dsi-bus.h         | 144 +++++++++++++++
 5 files changed, 484 insertions(+)

<snipped as far as mipi-dsi-bus.h

quoted

diff --git a/include/video/mipi-dsi-bus.h b/include/video/mipi-dsi-bus.h
new file mode 100644
index 0000000..a78792d
--- /dev/null
+++ b/include/video/mipi-dsi-bus.h

@@ -0,0 +1,144 @@
+/*
+ * MIPI DSI Bus
+ *
+ * Copyright (C) 2013, Samsung Electronics, Co., Ltd.
+ * Andrzej Hajda <a.hajda@samsung.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef __MIPI_DSI_BUS_H__
+#define __MIPI_DSI_BUS_H__
+
+#include <linux/device.h>
+#include <video/videomode.h>
+
+struct mipi_dsi_bus;
+struct mipi_dsi_device;
+
+struct mipi_dsi_bus_ops {
+	int (*set_power)(struct mipi_dsi_bus *bus, struct mipi_dsi_device

*dev,
+			 bool on);
+	int (*set_stream)(struct mipi_dsi_bus *bus, struct mipi_dsi_device
*dev,
+			  bool on);
+	int (*transfer)(struct mipi_dsi_bus *bus, struct mipi_dsi_device
*dev,
+			u8 type, const u8 *tx_buf, size_t tx_len, u8 *rx_buf,
+			size_t rx_len);
+};
+
+#define DSI_MODE_VIDEO			(1 << 0)
+#define DSI_MODE_VIDEO_BURST		(1 << 1)
+#define DSI_MODE_VIDEO_SYNC_PULSE	(1 << 2)
+#define DSI_MODE_VIDEO_AUTO_VERT	(1 << 3)
+#define DSI_MODE_VIDEO_HSE		(1 << 4)
+#define DSI_MODE_VIDEO_HFP		(1 << 5)
+#define DSI_MODE_VIDEO_HBP		(1 << 6)
+#define DSI_MODE_VIDEO_HSA		(1 << 7)
+#define DSI_MODE_VSYNC_FLUSH		(1 << 8)
+#define DSI_MODE_EOT_PACKET		(1 << 9)
+
+enum mipi_dsi_pixel_format {
+	DSI_FMT_RGB888,
+	DSI_FMT_RGB666,
+	DSI_FMT_RGB666_PACKED,
+	DSI_FMT_RGB565,
+};
+
+struct mipi_dsi_interface_params {
+	enum mipi_dsi_pixel_format format;
+	unsigned long mode;
+	unsigned long hs_clk_freq;
+	unsigned long esc_clk_freq;
+	unsigned char data_lanes;
+	unsigned char cmd_allow;
+};
+
+struct mipi_dsi_bus {
+	struct device *dev;
+	const struct mipi_dsi_bus_ops *ops;
+};
+
+#define MIPI_DSI_MODULE_PREFIX		"mipi-dsi:"
+#define MIPI_DSI_NAME_SIZE		32
+
+struct mipi_dsi_device_id {
+	char name[MIPI_DSI_NAME_SIZE];
+	__kernel_ulong_t driver_data	/* Data private to the driver */
+			__aligned(sizeof(__kernel_ulong_t));
+};
+
+struct mipi_dsi_device {
+	char name[MIPI_DSI_NAME_SIZE];
+	int id;
+	struct device dev;
+
+	const struct mipi_dsi_device_id *id_entry;
+	struct mipi_dsi_bus *bus;
+	struct videomode vm;
+	struct mipi_dsi_interface_params params;
+};
+
+#define to_mipi_dsi_device(d)	container_of(d, struct
mipi_dsi_device, dev)
+
+int mipi_dsi_device_register(struct mipi_dsi_device *dev,
+			     struct mipi_dsi_bus *bus);
+void mipi_dsi_device_unregister(struct mipi_dsi_device *dev);
+
+struct mipi_dsi_driver {
+	int(*probe)(struct mipi_dsi_device *);
+	int(*remove)(struct mipi_dsi_device *);
+	struct device_driver driver;
+	const struct mipi_dsi_device_id *id_table;
+};
+
+#define to_mipi_dsi_driver(d)	container_of(d, struct
mipi_dsi_driver, driver)
+
+int mipi_dsi_driver_register(struct mipi_dsi_driver *drv);
+void mipi_dsi_driver_unregister(struct mipi_dsi_driver *drv);
+
+static inline void *mipi_dsi_get_drvdata(const struct mipi_dsi_device
*dev)
+{
+	return dev_get_drvdata(&dev->dev);
+}
+
+static inline void mipi_dsi_set_drvdata(struct mipi_dsi_device *dev,
+					void *data)
+{
+	dev_set_drvdata(&dev->dev, data);
+}
+
+int of_mipi_dsi_register_devices(struct mipi_dsi_bus *bus);
+void mipi_dsi_unregister_devices(struct mipi_dsi_bus *bus);
+
+/* module_mipi_dsi_driver() - Helper macro for drivers that don't do
+ * anything special in module init/exit.  This eliminates a lot of
+ * boilerplate.  Each module may only use this macro once, and
+ * calling it replaces module_init() and module_exit()
+ */
+#define module_mipi_dsi_driver(__mipi_dsi_driver) \
+	module_driver(__mipi_dsi_driver, mipi_dsi_driver_register, \
+			mipi_dsi_driver_unregister)
+
+int mipi_dsi_set_power(struct mipi_dsi_device *dev, bool on);
+int mipi_dsi_set_stream(struct mipi_dsi_device *dev, bool on);
+int mipi_dsi_dcs_write(struct mipi_dsi_device *dev, int channel, const u8
*data,
+		       size_t len);
+int mipi_dsi_dcs_read(struct mipi_dsi_device *dev, int channel, u8 cmd,
+		      u8 *data, size_t len);
+
+#define mipi_dsi_dcs_write_seq(dev, channel, seq...) \
+({\
+	const u8 d[] = { seq };\
+	BUILD_BUG_ON_MSG(ARRAY_SIZE(d) > 64, "DCS sequence too long for
stack");\
+	mipi_dsi_dcs_write(dev, channel, d, ARRAY_SIZE(d));\
+})
+
+#define mipi_dsi_dcs_write_static_seq(dev, channel, seq...) \
+({\
+	static const u8 d[] = { seq };\
+	mipi_dsi_dcs_write(dev, channel, d, ARRAY_SIZE(d));\
+})
+
+#endif /* __MIPI_DSI_BUS__ */

I may well have missed something,
 but I can't see exactly how a command mode
update would be done with this interface. Would this require repeated calls to
.transfer? Such transfers would need to be flagged as requiring
synchronisation with a tearing effect control signal - either the inband
method or a dedicated line. I suspect many hardware implementations will have
a specific method for transferring pixel data in a DSI command mode transfer.

The command sending period during video mode should probably be configurable
on a per-transfer basis. Some commands have to be synchronised with vertical
blanking, others do not. This could perhaps be combined with a wider
configuration option for a given panel or interface. Similarly, selection of
low power (LP) and high speed (HS) mode on a per-transfer basis can be needed
for some panels.

Is there a mechanism for controlling ultra-low power state (ULPS) entry? Also,
is there a method for sending arbitrary trigger messages (eg the reset
trigger)?

Thanks for the feedback.
The current dsi bus implementation was just made to work with the
hw I have. It should be extended to be more generic, but I hope
now it is just matter of adding good opses and parameters.
Feel free to propose new opses.

Andrzej

Thanks,

Bert.