Hi,
I would like to write a DRM bridge driver that is an I2C device and a DRM MIPI DSI device.
It looks like that both - 'i2c-core.c: of_i2c_register_devices' and 'drm_mipi_dsi.c: mipi_dsi_host_register' are registering their devices by iterating over devicetree child nodes with for_each_available_child_of_node.
Since I can't make the bridge a child node of both, I don't know how to resolve it.
Best regards -Carsten
Hi,
I would like to write a DRM bridge driver that is an I2C device and a DRM
MIPI DSI device.
It looks like that both - 'i2c-core.c: of_i2c_register_devices' and
'drm_mipi_dsi.c: mipi_dsi_host_register' are registering their devices by iterating over devicetree child nodes with for_each_available_child_of_node.
Since I can't make the bridge a child node of both, I don't know how to
resolve it.
Found the answer myself. adv7533 driver is a good example. Devicetree exists for qcom apq8016-sbc. No need to make the bridge a MIPI DSI child node.
Best regards -Carsten
Hi Carsten,
On Wednesday, 4 April 2018 11:41:05 EEST Carsten Behling wrote:
Hi,
I would like to write a DRM bridge driver that is an I2C device and a DRM MIPI DSI device.
It looks like that both - 'i2c-core.c: of_i2c_register_devices' and 'drm_mipi_dsi.c: mipi_dsi_host_register' are registering their devices by iterating over devicetree child nodes with for_each_available_child_of_node.
Since I can't make the bridge a child node of both, I don't know how to resolve it.
Found the answer myself. adv7533 driver is a good example. Devicetree exists for qcom apq8016-sbc. No need to make the bridge a MIPI DSI child node.
This is an issue that has largely been ignored so far in Linux. Both DT and the Linux kernel device model organize devices in a tree structure based on the control buses. Devices that are connected to multiple control buses haven't been taken into account in the design and are thus hard to support.
As you may know, DSI can work in command mode or data mode. In data mode the DSI bus is only use to transfer video data, while in command mode it is also used to control the device (reading and writing registers).
A DSI device operating in data mode and controlled through I2C isn't a problem, as there's a single control bus in that case. The device should be a child of the I2C controller in DT, and will be instantiated through of_i2c_register_devices(). A DSI device operating in command mode without any other control bus isn't a problem either, it will be a child of the DSI master in DT, and will bee instantiated through mipi_dsi_host_register().
A DSI device operating in command mode that also require configuration through a separate control bus (such as I2C, but also SPI) is much more problematic to support. Fortunately those devices are rare. Hopefully your device won't fall in this category. If it does, we can discuss how to best support it.
On 05.04.2018 12:28, Laurent Pinchart wrote:
Hi Carsten,
On Wednesday, 4 April 2018 11:41:05 EEST Carsten Behling wrote:
Hi,
I would like to write a DRM bridge driver that is an I2C device and a DRM MIPI DSI device.
It looks like that both - 'i2c-core.c: of_i2c_register_devices' and 'drm_mipi_dsi.c: mipi_dsi_host_register' are registering their devices by iterating over devicetree child nodes with for_each_available_child_of_node.
Since I can't make the bridge a child node of both, I don't know how to resolve it.
Found the answer myself. adv7533 driver is a good example. Devicetree exists for qcom apq8016-sbc. No need to make the bridge a MIPI DSI child node.
This is an issue that has largely been ignored so far in Linux. Both DT and the Linux kernel device model organize devices in a tree structure based on the control buses. Devices that are connected to multiple control buses haven't been taken into account in the design and are thus hard to support.
As you may know, DSI can work in command mode or data mode. In data mode the DSI bus is only use to transfer video data, while in command mode it is also used to control the device (reading and writing registers).
I am not sure what you mean by data and command mode. MIPI DSI specs says about video and command mode - modes to transfer video data. In both cases DSI can be used to control the device.
A DSI device operating in data mode and controlled through I2C isn't a problem, as there's a single control bus in that case. The device should be a child of the I2C controller in DT, and will be instantiated through of_i2c_register_devices(). A DSI device operating in command mode without any other control bus isn't a problem either, it will be a child of the DSI master in DT, and will bee instantiated through mipi_dsi_host_register().
A DSI device operating in command mode that also require configuration through a separate control bus (such as I2C, but also SPI) is much more problematic to support. Fortunately those devices are rare. Hopefully your device won't fall in this category. If it does, we can discuss how to best support it.
As you have already found adv bridge is a good example. It is not clear from the emails if DSI is used only to send video, or also to control? And if to control, is it used to pass only specific commands
or can be used as alternative to i2c interface?
Regards
Andrzej
Hi Andrzej,
On Thursday, 5 April 2018 14:28:51 EEST Andrzej Hajda wrote:
On 05.04.2018 12:28, Laurent Pinchart wrote:
On Wednesday, 4 April 2018 11:41:05 EEST Carsten Behling wrote:
Hi,
I would like to write a DRM bridge driver that is an I2C device and a DRM MIPI DSI device.
It looks like that both - 'i2c-core.c: of_i2c_register_devices' and 'drm_mipi_dsi.c: mipi_dsi_host_register' are registering their devices by iterating over devicetree child nodes with for_each_available_child_of_node.
Since I can't make the bridge a child node of both, I don't know how to resolve it.
Found the answer myself. adv7533 driver is a good example. Devicetree exists for qcom apq8016-sbc. No need to make the bridge a MIPI DSI child node.
This is an issue that has largely been ignored so far in Linux. Both DT and the Linux kernel device model organize devices in a tree structure based on the control buses. Devices that are connected to multiple control buses haven't been taken into account in the design and are thus hard to support.
As you may know, DSI can work in command mode or data mode. In data mode the DSI bus is only use to transfer video data, while in command mode it is also used to control the device (reading and writing registers).
I am not sure what you mean by data and command mode. MIPI DSI specs says about video and command mode - modes to transfer video data. In both cases DSI can be used to control the device.
Sorry, I meant pure video mode, when a panel only uses DSI to receive video data but handles all control communication through a separate control bus.
A DSI device operating in data mode and controlled through I2C isn't a problem, as there's a single control bus in that case. The device should be a child of the I2C controller in DT, and will be instantiated through of_i2c_register_devices(). A DSI device operating in command mode without any other control bus isn't a problem either, it will be a child of the DSI master in DT, and will bee instantiated through mipi_dsi_host_register().
A DSI device operating in command mode that also require configuration through a separate control bus (such as I2C, but also SPI) is much more problematic to support. Fortunately those devices are rare. Hopefully your device won't fall in this category. If it does, we can discuss how to best support it.
As you have already found adv bridge is a good example. It is not clear from the emails if DSI is used only to send video, or also to control? And if to control, is it used to pass only specific commands or can be used as alternative to i2c interface?
Carsten, could you please provide more information about the panel you're using ?
2018-04-05 13:39 GMT+02:00 Laurent Pinchart <
laurent.pinchart@ideasonboard.com>:
Hi Andrzej,
On Thursday, 5 April 2018 14:28:51 EEST Andrzej Hajda wrote:
On 05.04.2018 12:28, Laurent Pinchart wrote:
On Wednesday, 4 April 2018 11:41:05 EEST Carsten Behling wrote:
Hi,
I would like to write a DRM bridge driver that is an I2C device and a DRM MIPI DSI device.
It looks like that both - 'i2c-core.c: of_i2c_register_devices' and 'drm_mipi_dsi.c: mipi_dsi_host_register' are registering their
devices
by iterating over devicetree child nodes with for_each_available_child_of_node.
Since I can't make the bridge a child node of both, I don't know how
to
resolve it.
Found the answer myself. adv7533 driver is a good example. Devicetree exists for qcom apq8016-sbc. No need to make the bridge a MIPI DSI
child
node.
This is an issue that has largely been ignored so far in Linux. Both DT and the Linux kernel device model organize devices in a tree structure based on the control buses. Devices that are connected to multiple
control
buses haven't been taken into account in the design and are thus hard to support.
As you may know, DSI can work in command mode or data mode. In data mode the DSI bus is only use to transfer video data, while in command mode it is also used to control the device (reading and writing registers).
I am not sure what you mean by data and command mode. MIPI DSI specs says about video and command mode - modes to transfer video data. In both cases DSI can be used to control the device.
Sorry, I meant pure video mode, when a panel only uses DSI to receive
video
data but handles all control communication through a separate control bus.
A DSI device operating in data mode and controlled through I2C isn't a problem, as there's a single control bus in that case. The device should be a child of the I2C controller in DT, and will be instantiated through of_i2c_register_devices(). A DSI device operating in command mode
without
any other control bus isn't a problem either, it will be a child of the DSI master in DT, and will bee instantiated through mipi_dsi_host_register().
A DSI device operating in command mode that also require configuration through a separate control bus (such as I2C, but also SPI) is much more problematic to support. Fortunately those devices are rare. Hopefully your device won't fall in this category. If it does, we can discuss how to best support it.
As you have already found adv bridge is a good example. It is not clear from the emails if DSI is used only to send video, or also to control? And if to control, is it used to pass only specific commands or can be used as alternative to i2c interface?
Carsten, could you please provide more information about the panel you're using ?
Sure, it's an TI SN65DSI84. It is just receiving pixel data on the input lines. I got an incomplete driver from Variscite that just writes a hardcoded I2C regmap from DTS. I'm currently writing a real DRM bridge driver based on that. I didn't find a better one.
Regards -Carsten
On 05.04.2018 13:51, Carsten Behling wrote:
2018-04-05 13:39 GMT+02:00 Laurent Pinchart
<laurent.pinchart@ideasonboard.com mailto:laurent.pinchart@ideasonboard.com>:
Hi Andrzej,
On Thursday, 5 April 2018 14:28:51 EEST Andrzej Hajda wrote:
On 05.04.2018 12:28, Laurent Pinchart wrote:
On Wednesday, 4 April 2018 11:41:05 EEST Carsten Behling wrote:
Hi,
I would like to write a DRM bridge driver that is an I2C device and a DRM MIPI DSI device.
It looks like that both - 'i2c-core.c: of_i2c_register_devices' and 'drm_mipi_dsi.c: mipi_dsi_host_register' are registering their devices by iterating over devicetree child nodes with for_each_available_child_of_node.
> Since I can't make the bridge a child node of both, I don't know how to resolve it.
Found the answer myself. adv7533 driver is a good example. Devicetree exists for qcom apq8016-sbc. No need to make the bridge a MIPI DSI child node.
This is an issue that has largely been ignored so far in Linux. Both DT and the Linux kernel device model organize devices in a tree structure based on the control buses. Devices that are connected to multiple
control
buses haven't been taken into account in the design and are thus hard to support.
As you may know, DSI can work in command mode or data mode. In data mode the DSI bus is only use to transfer video data, while in command mode it is also used to control the device (reading and writing registers).
I am not sure what you mean by data and command mode. MIPI DSI specs says about video and command mode - modes to transfer video data. In both cases DSI can be used to control the device.
Sorry, I meant pure video mode, when a panel only uses DSI to
receive video
data but handles all control communication through a separate
control bus.
A DSI device operating in data mode and controlled through I2C isn't a problem, as there's a single control bus in that case. The device
should
be a child of the I2C controller in DT, and will be instantiated
through
of_i2c_register_devices(). A DSI device operating in command mode
without
any other control bus isn't a problem either, it will be a child
of the
DSI master in DT, and will bee instantiated through mipi_dsi_host_register().
A DSI device operating in command mode that also require configuration through a separate control bus (such as I2C, but also SPI) is much
more
problematic to support. Fortunately those devices are rare. Hopefully your device won't fall in this category. If it does, we can
discuss how
to best support it.
As you have already found adv bridge is a good example. It is not clear from the emails if DSI is used only to send video, or also to control? And if to control, is it used to pass only specific commands or can be used as alternative to i2c interface?
Carsten, could you please provide more information about the panel you're using ?
Sure, it's an TI SN65DSI84. It is just receiving pixel data on the input lines. I got an incomplete driver from Variscite that just writes a hardcoded I2C regmap from DTS. I'm currently writing a real DRM bridge driver based on that. I didn't find a better one.
According to datasheet it looks like i2c controlled only DSI bridge, so adv driver should be a good reference.
Regards Andrzej
Regards -Carsten
dri-devel@lists.freedesktop.org
-
Andrzej Hajda -
Carsten Behling -
Laurent Pinchart