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

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Message-ID: <482ccf9c-fad5-470c-964f-a2c422f79555@collabora.com>
Date: Tue, 17 Dec 2024 15:49:18 +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>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
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 "airlied@...il.com" <airlied@...il.com>,
 "linux-arm-kernel@...ts.infradead.org"
 <linux-arm-kernel@...ts.infradead.org>,
 "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
 "junzhi.zhao@...iatek.com" <junzhi.zhao@...iatek.com>
Subject: Re: [PATCH v2 15/15] drm/mediatek: Introduce HDMI/DDC v2 for
 MT8195/MT8188

Il 17/12/24 10:21, 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 void mtk_hdmi_v2_bridge_pre_enable(struct drm_bridge *bridge,
>> +                                         struct drm_bridge_state *old_state)
>> +{
>> +       struct mtk_hdmi *hdmi = hdmi_ctx_from_bridge(bridge);
>> +       struct drm_atomic_state *state = old_state->base.state;
>> +       struct drm_connector_state *conn_state;
>> +       union phy_configure_opts opts = {
>> +               .dp = { .link_rate = hdmi->mode.clock * KILO }
>> +       };
>> +
>> +       /* Retrieve the connector through the atomic state */
>> +       hdmi->curr_conn = drm_atomic_get_new_connector_for_encoder(state, bridge->encoder);
>> +
>> +       conn_state = drm_atomic_get_new_connector_state(state, hdmi->curr_conn);
>> +       if (WARN_ON(!conn_state))
>> +               return;
>> +
>> +       /*
>> +        * Preconfigure the HDMI controller and the HDMI PHY at pre_enable
>> +        * stage to make sure that this IP is ready and clocked before the
>> +        * mtk_dpi gets powered on and before it enables the output.
> 
> In patch [6/15], you does not power on DPI power in DPI driver.
> Could you point out the code about 'mtk_dpi gets powered on'?
> 

DPI gets powered on in mtk_dpi_bridge_enable() -> mtk_dpi_power_on(dpi)

Cheers,
Angelo

> Regards,
> CK
> 
>> +        */
>> +       hdmi->dvi_mode = !hdmi->curr_conn->display_info.is_hdmi;
>> +       mtk_hdmi_v2_output_set_display_mode(hdmi, &hdmi->mode);
>> +
>> +       /* Reconfigure phy clock link with appropriate rate */
>> +       phy_configure(hdmi->phy, &opts);
>> +
>> +       /* Power on the PHY here to make sure that DPI_HDMI is clocked */
>> +       phy_power_on(hdmi->phy);
>> +
>> +       hdmi->powered = true;
>> +}
>> +
> 
>