linux-kernel - Re: [PATCH v2 15/15] drm/mediatek: Introduce HDMI/DDC v2 for MT8195/MT8188

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Message-ID: <e5788187-e894-4aab-a41e-a3d7a64762c6@collabora.com>
Date: Mon, 16 Dec 2024 12:04:06 +0100
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: CK Hu (胡俊光) <ck.hu@...iatek.com>,
 "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>
Cc: "robh@...nel.org" <robh@...nel.org>,
 "jie.qiu@...iatek.com" <jie.qiu@...iatek.com>,
 "tzimmermann@...e.de" <tzimmermann@...e.de>,
 "simona@...ll.ch" <simona@...ll.ch>, "mripard@...nel.org"
 <mripard@...nel.org>, Jitao Shi (石记涛)
 <jitao.shi@...iatek.com>,
 "linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
 "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
 "maarten.lankhorst@...ux.intel.com" <maarten.lankhorst@...ux.intel.com>,
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 "junzhi.zhao@...iatek.com" <junzhi.zhao@...iatek.com>
Subject: Re: [PATCH v2 15/15] drm/mediatek: Introduce HDMI/DDC v2 for
 MT8195/MT8188

Il 16/12/24 09:57, CK Hu (胡俊光) ha scritto:
> Hi, Angelo:
> 
> On Thu, 2024-12-05 at 12:45 +0100, AngeloGioacchino Del Regno wrote:
>> External email : Please do not click links or open attachments until you have verified the sender or the content.
>>
>>
>> Add support for the newer HDMI-TX (Encoder) v2 and DDC v2 IPs
>> found in MediaTek's MT8195, MT8188 SoC and their variants, and
>> including support for display modes up to 4k60 and for HDMI
>> Audio, as per the HDMI 2.0 spec.
>>
>> HDCP and CEC functionalities are also supported by this hardware,
>> but are not included in this commit and that also poses a slight
>> difference between the V2 and V1 controllers in how they handle
>> Hotplug Detection (HPD).
>>
>> While the v1 controller was using the CEC controller to check
>> HDMI cable connection and disconnection, in this driver the v2
>> one does not.
>>
>> This is due to the fact that on parts with v2 designs, like the
>> MT8195 SoC, there is one CEC controller shared between the HDMI
>> Transmitter (HDMI-TX) and Receiver (HDMI-RX): before eventually
>> adding support to use the CEC HW to wake up the HDMI controllers
>> it is necessary to have support for one TX, one RX *and* for both
>> at the same time.
>>
>> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
>> ---
> 
> [snip]
> 
>> +static int mtk_hdmi_v2_bridge_atomic_check(struct drm_bridge *bridge,
>> +                                          struct drm_bridge_state *bridge_state,
>> +                                          struct drm_crtc_state *crtc_state,
>> +                                          struct drm_connector_state *conn_state)
>> +{
> 
> I would like v1 and v2 has the same behavior.
> Why v2 has atomic check but v1 has no?
> If this is better to have, add atomic check to v1, and this function would be common function.
> 

That's because v2 uses the new helpers, while v1 does not.
The v1 must be converted to the new helpers in order to use atomic_check() like v2.

Cheers,
Angelo

> Regards,
> CK
> 
>> +       return drm_atomic_helper_connector_hdmi_check(conn_state->connector,
>> +                                                     conn_state->state);
>> +}
>> +
> 
>