linux-kernel - Re: [PATCH v7 0/4] drm: add support for Cadence MHDP DPI/DP bridge.

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Date:   Wed, 20 Mar 2019 11:33:46 +0200
From:   Tomi Valkeinen <tomi.valkeinen@...com>
To:     Damian Kos <dkos@...ence.com>
CC:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>, Sandy Huang <hjc@...k-chips.com>,
        Heiko Stübner <heiko@...ech.de>,
        <dri-devel@...ts.freedesktop.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-rockchip@...ts.infradead.org>, <jbergsagel@...com>,
        <quentin.schulz@...tlin.com>, <piotrs@...ence.com>,
        <rafalc@...ence.com>
Subject: Re: [PATCH v7 0/4] drm: add support for Cadence MHDP DPI/DP bridge.

Damian, ping.

On 31/01/2019 14:08, Tomi Valkeinen wrote:
> Hi,
> 
> On 30/01/2019 13:03, Damian Kos wrote:
>> Hello!
>>
>> This is the series of patches that will add support for the Cadence's DPI/DP
>> bridge. Please note that this is a preliminary version of the driver and there
>> will be more patches in the future with updates, fixes and improvements.
>> Please keep that in mind when looking at FIXME/TODO/XXX comments.
>>
>> Initially, MHDP driver was developed as a DRM bridge driver and was planed to
>> be placed in drivers/gpu/drm/bridge/mhdp.c.  However, there was already
>> a driver for Cadence's DP controller developed by RockChip, but that driver
>> uses the different DRM framework and looks like a part of a bigger system.
>> Both controllers (including firmware) are quite different internally
>> (MST/FEC/DSC support, link training done by driver, additional commands, IRQ's
>> etc.) but they have similar register map, except for Framer/Streamer (which is
>> noticeably different), so they appear similar.
>>
>> The following patches contain:
>> - Moving common code to drivers/gpu/drm/bridge/cdns-mhdp-common.* and
>>   modifying it a bit (mostly new prefixes for functions and data types) so it
>>   can be used by two, higher level, drivers.
>> - Modifying existing RockChip's DP driver to use the common code after changes
>>   made to it (use the new cdns_mhdp_device structure and new function names).
>> - Modifying DRM helpers a bit. Some are required for new driver, some are
>>   updates from DP 1.2 to 1.3 or 1.4.
>> - Adding documentation for device tree bindings.
>> - Adding preliminary Cadence DPI/DP bridge driver.
>>
>> Some of the things that will be added later on include (but are not limited
>> to):
>> - DSC support
>> - FEC support
>> - HDCP support
> 
> A few random comments/questions after a quick look at the patches.
> 
> The names of the source files and the kernel Kconfig are only about
> "Cadence DP". But the DT bindings is for cdns,mhdp8546, and the
> resulting module file is mhdp8546.ko. I think more consistency here
> would be good.
> 
> I presume the part number (or family? are there other similar parts with
> similar part numbers?) is relevant, so it should be in the Kconfig
> option and help text, and probably in the file names too. The module
> name should have "cdns" prefix there, similar to the source files and
> the cdns-dsi.ko.
> 
> Or maybe the same driver will handle all Cadence DP parts, in which case
> generic filenames are fine, but then the resulting kernel module should
> also be just "cdns-mhdp.ko".
> 
> I see some audio functions in the code, but it's not mentioned in the DT
> bindings. I'm not an audio guy, but the display bridges with audio
> support I have seen have had DT bindings for the audio source too. Is
> audio supported in the current driver?
> 
>  Tomi
> 

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