[PATCH v1 3/3] drm/stm: Add STM32 DSI host driver

[Philippe CORNU]

Hi Neil,
Many thanks for your comments.

The PHY part of the MIPI DSI is the main difference between all chipsets 
based on the Synopsys DesignWare MIPI DSI.
There is no "generic DSI PHY interface" and that is probably why all soc 
vendors have implemented their own drivers (RockChip, NXP/Freescale, 
HiSilicon and now STM32).

Regarding creating a "generic dw MIPI DSI bridge" as the recent dw hdmi 
bridge, several attempts have been done in the past but without success:
* Liu Ying from Freescale in February 2015 
(https://lkml.org/lkml/2015/2/12/38).
* Chris Zhong from Rockchip in November 2015 
(http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1024586.html).

The Rockchip driver looks nice and is updated regularly.
So, instead of creating a new driver for the STM32 family, we decided to 
use Rockchip’s in our own drm/stm directory and replace the 
Rockchip-specific PHY by the STM32.

Comments are welcome :-)
Many thanks,
Philippe


On 05/15/2017 10:22 AM, Neil Armstrong wrote:
> On 05/12/2017 04:56 PM, Philippe CORNU wrote:
>> This mipi dsi host driver is based on the Rockchip version of the
>> Synopsys Designware mipi dsi driver (rockchip/dw-mipi-dsi.c)
>> modified for the stm32 family:
>> - replace Rockchip digital & phy specific extensions with stm32's ones.
>> - add a bridge
>>
>> Signed-off-by: Philippe CORNU <philippe.cornu at st.com>
>> ---
>>  drivers/gpu/drm/stm/Kconfig       |    7 +
>>  drivers/gpu/drm/stm/Makefile      |    2 +
>>  drivers/gpu/drm/stm/dw-mipi-dsi.c | 1197 +++++++++++++++++++++++++++++++++++++
>>  3 files changed, 1206 insertions(+)
>>  create mode 100644 drivers/gpu/drm/stm/dw-mipi-dsi.c
>>
>> diff --git a/drivers/gpu/drm/stm/Kconfig b/drivers/gpu/drm/stm/Kconfig
>> index 2c4817f..0007789 100644
>> --- a/drivers/gpu/drm/stm/Kconfig
>> +++ b/drivers/gpu/drm/stm/Kconfig
>> @@ -14,3 +14,10 @@ config DRM_STM
>>  	  STMicroelectronics STM32 MCUs.
>>  	  To compile this driver as a module, choose M here: the module
>>  	  will be called stm-drm.
>> +
>> +config DRM_STM_DSI
>> +	tristate "MIPI DSI support for STMicroelectronics SoC"
>> +	depends on DRM_STM
>> +	select DRM_MIPI_DSI
>> +	help
>> +	  Choose this option for MIPI DSI support on STMicroelectronics SoC.
>> diff --git a/drivers/gpu/drm/stm/Makefile b/drivers/gpu/drm/stm/Makefile
>> index e114d45..e448a93 100644
>> --- a/drivers/gpu/drm/stm/Makefile
>> +++ b/drivers/gpu/drm/stm/Makefile
>> @@ -4,4 +4,6 @@ stm-drm-y := \
>>  	drv.o \
>>  	ltdc.o
>>
>> +obj-$(CONFIG_DRM_STM_DSI) += dw-mipi-dsi.o
>> +
>>  obj-$(CONFIG_DRM_STM) += stm-drm.o
>> diff --git a/drivers/gpu/drm/stm/dw-mipi-dsi.c b/drivers/gpu/drm/stm/dw-mipi-dsi.c
>> new file mode 100644
>> index 0000000..4b7f7b9
>> --- /dev/null
>> +++ b/drivers/gpu/drm/stm/dw-mipi-dsi.c
>
>
> Hi Philippe,
>
> First question, why couldn't this be transformed as a bridge driver along the Synopsys DW-HDMI driver ?
>
> Neil
>