[PATCH 1/2] drm/bridge: add Silicon Image SiI9234 driver

[Marek Szyprowski]

Hi Laurent,

Thanks for your detailed comments. Maciej resurrected some orphaned code,
which is still useful today (Tomasz has left Samsung a few years ago).
I'm not sure we will be able to answer all your questions without deep
investigation, especially about the driver operation details, but we
will try.

On 2017-08-03 12:24, Laurent Pinchart wrote:
> Hi Maciej,
>
> Thank you for the patch.
>
> On Thursday 03 Aug 2017 09:45:22 Maciej Purski wrote:
>> SiI9234 transmitter converts eTMDS/HDMI signal to MHL 1.0.
>> It is controlled via I2C bus. Its interaction with other
>> devices in video pipeline is performed mainly on HW level.
>> The only interaction it does on device driver level is
>> filtering-out unsupported video modes, it exposes drm_bridge
>> interface to perform this operation.
>>
>> This patch is based on the code refactored by Tomasz Stanislawski
>> <t.stanislaws at samsung.com>, which was initially developed by:
>> Adam Hampson <ahampson at sta.samsung.com>
>> Erik Gilling <konkers at android.com>
>> Shankar Bandal <shankar.b at samsung.com>
>> Dharam Kumar <dharam.kr at samsung.com>
>>
>> Signed-off-by: Maciej Purski <m.purski at samsung.com>
>> ---
>>   .../devicetree/bindings/display/bridge/sii9234.txt |   20 +
>>   drivers/gpu/drm/bridge/Kconfig                     |    8 +
>>   drivers/gpu/drm/bridge/Makefile                    |    1 +
>>   drivers/gpu/drm/bridge/sii9234.c                   | 1019 +++++++++++++++++
>>   4 files changed, 1048 insertions(+)
>>   create mode 100644
>> Documentation/devicetree/bindings/display/bridge/sii9234.txt create mode
>> 100644 drivers/gpu/drm/bridge/sii9234.c
>>
>> diff --git a/Documentation/devicetree/bindings/display/bridge/sii9234.txt
>> b/Documentation/devicetree/bindings/display/bridge/sii9234.txt new file
>> mode 100644
>> index 0000000..2cdf286
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/display/bridge/sii9234.txt
> DT reviewers might ask you to submit DT bindings as a separate patch.
>
>> @@ -0,0 +1,20 @@
>> +SiI9234 Mobile HD Link Transmitter
>> +
>> +Required properties:
>> +- compatible : "sil,sii9234".
>> +- reg : I2C address for TPI interface, use 0x39
>> +- vcc-supply : regulator that supplies the chip
> Is there a single power supply only ? Transceivers usually have at least one
> digital and one analog power supply.

Acording to the schematic there are four power supplies used for SII9234 
MHL chip in
Trats2 board: VSIL_1.2A, VSIL_1.2C, VCC_3.3V_MHL and VCC_1.8V_MHL. First 
two are
derived directly from VSIL_1.2 signal, which is modeled as a fixed 
regulator. The
latter two are derived directly from VBAT using some level converter, 
which is
controlled by the same GPIO pin as VSIL fixed regulator. Any idea how 
this should
be represented better in device tree instead of having single vcc-supply?

>
>> +- interrupts, interrupt-parent: interrupt specifier of INT pin
>> +- reset-gpios: gpio specifier of RESET pin
> Is this mandatory to connect the reset pin to the SoC ?

IMHO yes, the chip has to be reset during the initialization procedure 
and doesn't
work properly without reset.

> > [...] 

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland