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Message-ID: <e6337c08e2c40653b4a6542f1dd9fc350036b8c5.camel@mediatek.com>
Date: Mon, 1 Sep 2025 07:08:13 +0000
From: CK Hu (胡俊光) <ck.hu@...iatek.com>
To: "simona@...ll.ch" <simona@...ll.ch>, Mac Shen (沈俊)
<Mac.Shen@...iatek.com>, AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com>, "chunkuang.hu@...nel.org"
<chunkuang.hu@...nel.org>, "airlied@...il.com" <airlied@...il.com>,
Project_Global_Chrome_Upstream_Group
<Project_Global_Chrome_Upstream_Group@...iatek.com>, "p.zabel@...gutronix.de"
<p.zabel@...gutronix.de>, "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
Peng Liu (刘鹏) <Peng.Liu@...iatek.com>,
LIANKUN YANG (杨连坤) <Liankun.Yang@...iatek.com>
CC: "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 1/1] drm/mediatek: Adjust bandwidth limit for DP
On Fri, 2025-08-22 at 20:04 +0800, Liankun Yang wrote:
> By adjusting the order of link training and relocating it to HPD,
> link training can identify the usability of each lane in the current link.
>
> It also supports handling signal instability and weakness due to
> environmental issues, enabling the acquisition of a stable bandwidth
> for the current link. Subsequently, DP work can proceed based on
> the actual maximum bandwidth.
>
> It should training in the hpd event thread.
> Check the mode with lane count and link rate of training.
>
> If we're eDP and capabilities were already parsed we can skip
> reading again because eDP panels aren't hotpluggable hence the
> caps and training information won't ever change in a boot life
>
> Therefore, bridge typec judgment is required for edp training in
> atomic_enable function.
>
> Signed-off-by: Liankun Yang <liankun.yang@...iatek.com>
> ---
> Change in V6:
> - Fixed power on in atomic enable.
> - Fixed parse capability for edp.
> Per suggestion from the previous thread:
> https://urldefense.com/v3/__https://patchwork.kernel.org/project/linux-mediatek/patch/20250630080824.7107-1-liankun.yang@mediatek.com/__;!!CTRNKA9wMg0ARbw!kSLrY_ehXtIJ21a_ljnX7EmDtD92n8RfjW9Jee6qRfKzC8ekpkvvRcMoJRIo03WgQAm_L7R3zKrr5kS1FUKM6ag$
>
> Change in V5:
> - Fixed the issue that the 4th version of the patch caused DP to have no screen.
> Per suggestion from the previous thread:
> https://urldefense.com/v3/__https://patchwork.kernel.org/project/linux-mediatek/patch/20250625095446.31726-1-liankun.yang@mediatek.com/__;!!CTRNKA9wMg0ARbw!kSLrY_ehXtIJ21a_ljnX7EmDtD92n8RfjW9Jee6qRfKzC8ekpkvvRcMoJRIo03WgQAm_L7R3zKrr5kS1Nx-fs5M$
>
> Change in V4:
> - Tested the internal eDP display on MT8195 Tomato and it is fine.
> Per suggestion from the previous thread:
> https://urldefense.com/v3/__https://patchwork.kernel.org/project/linux-mediatek/patch/20250318140236.13650-2-liankun.yang@mediatek.com/__;!!CTRNKA9wMg0ARbw!kSLrY_ehXtIJ21a_ljnX7EmDtD92n8RfjW9Jee6qRfKzC8ekpkvvRcMoJRIo03WgQAm_L7R3zKrr5kS1osP1SG0$
>
> Change in V3:
> - Remove 'mtk_dp->enabled = false" in atomic disable.
> - Remove 'mtk_dp->enabled = true" in atomic enable.
> Per suggestion from the previous thread:
> https://urldefense.com/v3/__https://patchwork.kernel.org/project/linux-mediatek/patch/20241025083036.8829-4-liankun.yang@mediatek.com/__;!!CTRNKA9wMg0ARbw!kSLrY_ehXtIJ21a_ljnX7EmDtD92n8RfjW9Jee6qRfKzC8ekpkvvRcMoJRIo03WgQAm_L7R3zKrr5kS1MjQ5GiU$
>
> Change in V2:
> - Adjust DP training timing.
> - Adjust parse capabilities timing.
> - Add power on/off for connect/disconnect.
> Per suggestion from the previous thread:
> https://urldefense.com/v3/__https://patchwork.kernel.org/project/linux-mediatek/patch/20240315015233.2023-1-liankun.yang@mediatek.com/__;!!CTRNKA9wMg0ARbw!kSLrY_ehXtIJ21a_ljnX7EmDtD92n8RfjW9Jee6qRfKzC8ekpkvvRcMoJRIo03WgQAm_L7R3zKrr5kS1iJHpMzY$
> ---
> drivers/gpu/drm/mediatek/mtk_dp.c | 41 ++++++++++++++++++++++++-------
> 1 file changed, 32 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
> index bef6eeb30d3e..384496e49118 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dp.c
> @@ -1976,6 +1976,7 @@ static irqreturn_t mtk_dp_hpd_event_thread(int hpd, void *dev)
> struct mtk_dp *mtk_dp = dev;
> unsigned long flags;
> u32 status;
> + int ret;
>
> if (mtk_dp->need_debounce && mtk_dp->train_info.cable_plugged_in)
> msleep(100);
> @@ -1994,9 +1995,28 @@ static irqreturn_t mtk_dp_hpd_event_thread(int hpd, void *dev)
> memset(&mtk_dp->info.audio_cur_cfg, 0,
> sizeof(mtk_dp->info.audio_cur_cfg));
>
> + mtk_dp->enabled = false;
I'm not sure eDP would have hot-plug event or not.
If eDP also has hot-plug event (once), add do this only for DP
if (mtk_dp->data->bridge_type != DRM_MODE_CONNECTOR_eDP) {
/* Action only for DP */
}
> + /* power off aux */
> + mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
> + DP_PWR_STATE_BANDGAP_TPLL,
> + DP_PWR_STATE_MASK);
Why not use mtk_dp_aux_panel_poweron(mtk_dp, false)?
When plug in, you call mtk_dp_aux_panel_poweron(mtk_dp, true),
I would like it to be symmetric.
If not symmetric, add comment to describe why it's not symmetric.
> +
> mtk_dp->need_debounce = false;
> mod_timer(&mtk_dp->debounce_timer,
> jiffies + msecs_to_jiffies(100) - 1);
> + } else {
> + mtk_dp_aux_panel_poweron(mtk_dp, true);
> +
> + ret = mtk_dp_parse_capabilities(mtk_dp);
> + if (ret)
> + drm_err(mtk_dp->drm_dev, "Can't parse capabilities\n");
> +
> + /* Training */
> + ret = mtk_dp_training(mtk_dp);
> + if (ret)
> + drm_err(mtk_dp->drm_dev, "Training failed, %d\n", ret);
> +
> + mtk_dp->enabled = true;
> }
> }
>
> @@ -2167,7 +2187,8 @@ static const struct drm_edid *mtk_dp_edid_read(struct drm_bridge *bridge,
> * Parse capability here to let atomic_get_input_bus_fmts and
> * mode_valid use the capability to calculate sink bitrates.
> */
> - if (mtk_dp_parse_capabilities(mtk_dp)) {
> + if (mtk_dp->bridge.type == DRM_MODE_CONNECTOR_eDP &&
> + mtk_dp_parse_capabilities(mtk_dp)) {
I think this modification is related to what you say:
"If we're eDP and capabilities were already parsed we can skip
reading again because eDP panels aren't hotpluggable hence the
caps and training information won't ever change in a boot life"
I think this modification is not related to the title.
This is to improve eDP function not DP.
So separate this to another patch.
> drm_err(mtk_dp->drm_dev, "Can't parse capabilities\n");
> drm_edid_free(drm_edid);
> drm_edid = NULL;
> @@ -2355,6 +2376,7 @@ static void mtk_dp_bridge_atomic_enable(struct drm_bridge *bridge,
> struct drm_atomic_state *state)
> {
> struct mtk_dp *mtk_dp = mtk_dp_from_bridge(bridge);
> + bool enabled = mtk_dp->enabled;
> int ret;
>
> mtk_dp->conn = drm_atomic_get_new_connector_for_encoder(state,
> @@ -2365,13 +2387,16 @@ static void mtk_dp_bridge_atomic_enable(struct drm_bridge *bridge,
> return;
> }
>
> - mtk_dp_aux_panel_poweron(mtk_dp, true);
> + if (!enabled)
> + mtk_dp_aux_panel_poweron(mtk_dp, true);
>
> - /* Training */
> - ret = mtk_dp_training(mtk_dp);
> - if (ret) {
> - drm_err(mtk_dp->drm_dev, "Training failed, %d\n", ret);
> - goto power_off_aux;
> + if (mtk_dp->data->bridge_type == DRM_MODE_CONNECTOR_eDP) {
> + /* Training */
> + ret = mtk_dp_training(mtk_dp);
> + if (ret) {
> + drm_err(mtk_dp->drm_dev, "Training failed, %d\n", ret);
> + goto power_off_aux;
> + }
> }
if (mtk_dp->data->bridge_type == DRM_MODE_CONNECTOR_eDP) {
mtk_dp_aux_panel_poweron(mtk_dp, true);
/* Training */
ret = mtk_dp_training(mtk_dp);
if (ret) {
drm_err(mtk_dp->drm_dev, "Training failed, %d\n", ret);
goto power_off_aux;
}
}
>
> ret = mtk_dp_video_config(mtk_dp);
> @@ -2391,7 +2416,6 @@ static void mtk_dp_bridge_atomic_enable(struct drm_bridge *bridge,
> sizeof(mtk_dp->info.audio_cur_cfg));
> }
>
> - mtk_dp->enabled = true;
if (mtk_dp->data->bridge_type == DRM_MODE_CONNECTOR_eDP)
mtk_dp->enabled = true;
> mtk_dp_update_plugged_status(mtk_dp);
>
> return;
> @@ -2406,7 +2430,6 @@ static void mtk_dp_bridge_atomic_disable(struct drm_bridge *bridge,
> {
> struct mtk_dp *mtk_dp = mtk_dp_from_bridge(bridge);
>
> - mtk_dp->enabled = false;
if (mtk_dp->data->bridge_type == DRM_MODE_CONNECTOR_eDP)
mtk_dp->enabled = false;
Regards,
CK
> mtk_dp_update_plugged_status(mtk_dp);
> mtk_dp_video_enable(mtk_dp, false);
> mtk_dp_audio_mute(mtk_dp, true);
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